| // Copyright 2023 The Dawn & Tint Authors | 
 | // | 
 | // Redistribution and use in source and binary forms, with or without | 
 | // modification, are permitted provided that the following conditions are met: | 
 | // | 
 | // 1. Redistributions of source code must retain the above copyright notice, this | 
 | //    list of conditions and the following disclaimer. | 
 | // | 
 | // 2. Redistributions in binary form must reproduce the above copyright notice, | 
 | //    this list of conditions and the following disclaimer in the documentation | 
 | //    and/or other materials provided with the distribution. | 
 | // | 
 | // 3. Neither the name of the copyright holder nor the names of its | 
 | //    contributors may be used to endorse or promote products derived from | 
 | //    this software without specific prior written permission. | 
 | // | 
 | // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" | 
 | // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | 
 | // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE | 
 | // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE | 
 | // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | 
 | // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR | 
 | // SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER | 
 | // CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, | 
 | // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE | 
 | // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | 
 |  | 
 | #include "src/tint/lang/spirv/reader/parser/parser.h" | 
 |  | 
 | #include <algorithm> | 
 | #include <list> | 
 | #include <memory> | 
 | #include <string> | 
 | #include <unordered_map> | 
 | #include <unordered_set> | 
 | #include <utility> | 
 | #include <vector> | 
 |  | 
 | // This header is in an external dependency, so warnings cannot be fixed without upstream changes. | 
 | TINT_BEGIN_DISABLE_WARNING(NEWLINE_EOF); | 
 | TINT_BEGIN_DISABLE_WARNING(OLD_STYLE_CAST); | 
 | TINT_BEGIN_DISABLE_WARNING(SIGN_CONVERSION); | 
 | TINT_BEGIN_DISABLE_WARNING(WEAK_VTABLES); | 
 | TINT_BEGIN_DISABLE_WARNING(UNSAFE_BUFFER_USAGE); | 
 | #include "source/opt/build_module.h" | 
 | #include "source/opt/split_combined_image_sampler_pass.h" | 
 | TINT_END_DISABLE_WARNING(UNSAFE_BUFFER_USAGE); | 
 | TINT_END_DISABLE_WARNING(WEAK_VTABLES); | 
 | TINT_END_DISABLE_WARNING(SIGN_CONVERSION); | 
 | TINT_END_DISABLE_WARNING(OLD_STYLE_CAST); | 
 | TINT_END_DISABLE_WARNING(NEWLINE_EOF); | 
 |  | 
 | #include "src/tint/lang/core/ir/builder.h" | 
 | #include "src/tint/lang/core/ir/module.h" | 
 | #include "src/tint/lang/core/ir/referenced_module_vars.h" | 
 | #include "src/tint/lang/core/type/builtin_structs.h" | 
 | #include "src/tint/lang/spirv/builtin_fn.h" | 
 | #include "src/tint/lang/spirv/ir/builtin_call.h" | 
 | #include "src/tint/lang/spirv/type/explicit_layout_array.h" | 
 | #include "src/tint/lang/spirv/type/image.h" | 
 | #include "src/tint/lang/spirv/type/sampled_image.h" | 
 | #include "src/tint/lang/spirv/validate/validate.h" | 
 |  | 
 | using namespace tint::core::number_suffixes;  // NOLINT | 
 | using namespace tint::core::fluent_types;     // NOLINT | 
 |  | 
 | namespace tint::spirv::reader { | 
 |  | 
 | namespace { | 
 |  | 
 | // Stores information for operands which need to be calculated after a block is complete. Because | 
 | // a phi can store values which come after it, we can't calculate the value when the `OpPhi` is | 
 | // seen. | 
 | struct ReplacementValue { | 
 |     // The terminator instruction the operand belongs to | 
 |     core::ir::Terminator* terminator; | 
 |     // The operand index in `terminator` to replace | 
 |     uint32_t idx; | 
 |     // The SPIR-V value id to create the value from | 
 |     uint32_t value_id; | 
 | }; | 
 |  | 
 | /// The SPIR-V environment that we validate against. | 
 | constexpr auto kTargetEnv = SPV_ENV_VULKAN_1_1; | 
 |  | 
 | /// PIMPL class for SPIR-V parser. | 
 | /// Validates the SPIR-V module and then parses it to produce a Tint IR module. | 
 | class Parser { | 
 |   public: | 
 |     explicit Parser(const Options& options) : options_(options) {} | 
 |     ~Parser() = default; | 
 |  | 
 |     /// @param spirv the SPIR-V binary data | 
 |     /// @returns the generated SPIR-V IR module on success, or failure | 
 |     Result<core::ir::Module> Run(Slice<const uint32_t> spirv) { | 
 |         // Validate the incoming SPIR-V binary. | 
 |         auto result = validate::Validate(spirv, kTargetEnv); | 
 |         if (result != Success) { | 
 |             return result.Failure(); | 
 |         } | 
 |  | 
 |         // Build the SPIR-V tools internal representation of the SPIR-V module. | 
 |         spvtools::Context context(kTargetEnv); | 
 |         spirv_context_ = | 
 |             spvtools::BuildModule(kTargetEnv, context.CContext()->consumer, spirv.data, spirv.len); | 
 |         if (!spirv_context_) { | 
 |             return Failure("failed to build the internal representation of the module"); | 
 |         } | 
 |  | 
 |         { | 
 |             spvtools::opt::SplitCombinedImageSamplerPass pass; | 
 |             auto status = pass.Run(spirv_context_.get()); | 
 |             if (status == spvtools::opt::Pass::Status::Failure) { | 
 |                 return Failure("failed to run SplitCombinedImageSamplerPass in SPIR-V opt"); | 
 |             } | 
 |         } | 
 |  | 
 |         // Check for unsupported extensions. | 
 |         for (const auto& ext : spirv_context_->extensions()) { | 
 |             auto name = ext.GetOperand(0).AsString(); | 
 |             if (name != "SPV_KHR_storage_buffer_storage_class" && | 
 |                 name != "SPV_KHR_non_semantic_info" &&  // | 
 |                 // TODO(423644565): We assume the barriers are correct. We should check for any | 
 |                 // operation that makes barrier assumptions that aren't consistent with WGSL and | 
 |                 // generate the needed barriers. | 
 |                 name != "SPV_KHR_vulkan_memory_model") { | 
 |                 return Failure("SPIR-V extension '" + name + "' is not supported"); | 
 |             } | 
 |         } | 
 |  | 
 |         // Register imported instruction sets | 
 |         for (const auto& import : spirv_context_->ext_inst_imports()) { | 
 |             auto name = import.GetInOperand(0).AsString(); | 
 |  | 
 |             // TODO(dneto): Handle other extended instruction sets when needed. | 
 |             if (name == "GLSL.std.450") { | 
 |                 glsl_std_450_imports_.insert(import.result_id()); | 
 |             } else if (name.find("NonSemantic.") == 0) { | 
 |                 ignored_imports_.insert(import.result_id()); | 
 |             } else { | 
 |                 return Failure("Unrecognized extended instruction set: " + name); | 
 |             } | 
 |         } | 
 |  | 
 |         RegisterNames(); | 
 |  | 
 |         id_stack_.emplace_back(); | 
 |         { | 
 |             TINT_SCOPED_ASSIGNMENT(current_block_, ir_.root_block); | 
 |             EmitSpecConstants(); | 
 |             EmitModuleScopeVariables(); | 
 |         } | 
 |  | 
 |         EmitFunctions(); | 
 |         EmitEntryPointAttributes(); | 
 |  | 
 |         // TODO(crbug.com/tint/1907): Handle annotation instructions. | 
 |  | 
 |         RemapSamplers(); | 
 |         RemapBufferBlockAddressSpace(); | 
 |         AddRefToOutputsIfNeeded(); | 
 |  | 
 |         return std::move(ir_); | 
 |     } | 
 |  | 
 |     // If the spir-v struct was marked as `BufferBlock` then we always treat this as a storage | 
 |     // address space. We do this as a post-pass because we have to propagate the change through all | 
 |     // the types that derive from the buffer block, e.g. any access needs to change from `Uniform` | 
 |     // to `Storage` address space. | 
 |     void RemapBufferBlockAddressSpace() { | 
 |         for (auto* inst : *ir_.root_block) { | 
 |             auto* var = inst->As<core::ir::Var>(); | 
 |             if (!var) { | 
 |                 continue; | 
 |             } | 
 |  | 
 |             auto* ptr = var->Result()->Type()->As<core::type::Pointer>(); | 
 |             TINT_ASSERT(ptr); | 
 |  | 
 |             auto* str = ptr->UnwrapPtr()->As<core::type::Struct>(); | 
 |             if (!str) { | 
 |                 continue; | 
 |             } | 
 |             if (!storage_buffer_types_.contains(str)) { | 
 |                 continue; | 
 |             } | 
 |             auto iter = var_to_original_access_mode_.find(var); | 
 |             TINT_ASSERT(iter != var_to_original_access_mode_.end()); | 
 |             auto access_mode = iter->second; | 
 |  | 
 |             var->Result()->SetType(ty_.ptr(core::AddressSpace::kStorage, str, access_mode)); | 
 |             UpdateUsagesToStorageAddressSpace(var->Result(), access_mode); | 
 |         } | 
 |     } | 
 |  | 
 |     void UpdateUsagesToStorageAddressSpace(core::ir::Value* val, core::Access access_mode) { | 
 |         for (auto& usage : val->UsagesUnsorted()) { | 
 |             if (usage->instruction->Results().IsEmpty()) { | 
 |                 continue; | 
 |             } | 
 |  | 
 |             auto* res = usage->instruction->Result(); | 
 |             auto* ptr = res->Type()->As<core::type::Pointer>(); | 
 |             if (!ptr) { | 
 |                 continue; | 
 |             } | 
 |             TINT_ASSERT(ptr->AddressSpace() == core::AddressSpace::kUniform); | 
 |  | 
 |             res->SetType(ty_.ptr(core::AddressSpace::kStorage, ptr->StoreType(), access_mode)); | 
 |             UpdateUsagesToStorageAddressSpace(res, access_mode); | 
 |         } | 
 |     } | 
 |  | 
 |     void AddRefToOutputsIfNeeded() { | 
 |         for (auto& entry_point : spirv_context_->module()->entry_points()) { | 
 |             uint32_t spv_id = entry_point.GetSingleWordInOperand(1); | 
 |             TINT_ASSERT(functions_.Contains(spv_id)); | 
 |  | 
 |             auto* func = *(functions_.Get(spv_id)); | 
 |             for (uint32_t i = 3; i < entry_point.NumInOperands(); ++i) { | 
 |                 auto* val = Value(entry_point.GetSingleWordInOperand(i)); | 
 |                 b_.Phony(val)->InsertBefore(func->Block()->Front()); | 
 |             } | 
 |         } | 
 |     } | 
 |  | 
 |     void RemapSamplers() { | 
 |         for (auto* inst : *ir_.root_block) { | 
 |             auto* var = inst->As<core::ir::Var>(); | 
 |             if (!var) { | 
 |                 continue; | 
 |             } | 
 |             auto* ptr = var->Result()->Type()->As<core::type::Pointer>(); | 
 |             TINT_ASSERT(ptr); | 
 |  | 
 |             if (!ptr->StoreType()->As<core::type::Sampler>()) { | 
 |                 continue; | 
 |             } | 
 |  | 
 |             TINT_ASSERT(var->BindingPoint().has_value()); | 
 |  | 
 |             auto bp = var->BindingPoint().value(); | 
 |             auto used = used_bindings.GetOrAddZero(bp); | 
 |  | 
 |             // Only one use is the sampler itself. | 
 |             if (used == 1) { | 
 |                 continue; | 
 |             } | 
 |  | 
 |             auto& binding = max_binding.GetOrAddZero(bp.group); | 
 |             binding += 1; | 
 |  | 
 |             var->SetBindingPoint(bp.group, binding); | 
 |         } | 
 |     } | 
 |  | 
 |     std::optional<uint16_t> GetSpecId(const spvtools::opt::Instruction& inst) { | 
 |         auto decos = | 
 |             spirv_context_->get_decoration_mgr()->GetDecorationsFor(inst.result_id(), true); | 
 |         for (const auto* deco_inst : decos) { | 
 |             TINT_ASSERT(deco_inst->opcode() == spv::Op::OpDecorate); | 
 |  | 
 |             if (deco_inst->GetSingleWordInOperand(1) == | 
 |                 static_cast<uint32_t>(spv::Decoration::SpecId)) { | 
 |                 return {static_cast<uint16_t>(deco_inst->GetSingleWordInOperand(2))}; | 
 |             } | 
 |         } | 
 |         return std::nullopt; | 
 |     } | 
 |  | 
 |     void CreateOverride(const spvtools::opt::Instruction& inst, | 
 |                         core::ir::Value* value, | 
 |                         std::optional<uint16_t> spec_id) { | 
 |         auto* override_ = b_.Override(Type(inst.type_id())); | 
 |         override_->SetInitializer(value); | 
 |  | 
 |         if (spec_id.has_value()) { | 
 |             override_->SetOverrideId(OverrideId{spec_id.value()}); | 
 |         } | 
 |  | 
 |         Emit(override_, inst.result_id()); | 
 |  | 
 |         Symbol name = GetSymbolFor(inst.result_id()); | 
 |         if (name.IsValid()) { | 
 |             ir_.SetName(override_, name); | 
 |         } | 
 |     } | 
 |  | 
 |     // Generate a module-scope const declaration for each instruction | 
 |     // that is OpSpecConstantTrue, OpSpecConstantFalse, or OpSpecConstant. | 
 |     void EmitSpecConstants() { | 
 |         for (auto& inst : spirv_context_->types_values()) { | 
 |             switch (inst.opcode()) { | 
 |                 case spv::Op::OpSpecConstantTrue: | 
 |                 case spv::Op::OpSpecConstantFalse: { | 
 |                     auto* value = b_.Value(inst.opcode() == spv::Op::OpSpecConstantTrue); | 
 |                     auto spec_id = GetSpecId(inst); | 
 |  | 
 |                     if (spec_id.has_value()) { | 
 |                         CreateOverride(inst, value, spec_id); | 
 |                     } else { | 
 |                         // No spec_id means treat this as a constant. | 
 |                         AddValue(inst.result_id(), value); | 
 |                     } | 
 |                     break; | 
 |                 } | 
 |                 case spv::Op::OpSpecConstant: { | 
 |                     auto literal = inst.GetSingleWordInOperand(0); | 
 |                     auto* ty = spirv_context_->get_type_mgr()->GetType(inst.type_id()); | 
 |  | 
 |                     auto* constant = | 
 |                         spirv_context_->get_constant_mgr()->GetConstant(ty, std::vector{literal}); | 
 |  | 
 |                     core::ir::Value* value = tint::Switch( | 
 |                         Type(ty),  // | 
 |                         [&](const core::type::I32*) { | 
 |                             return b_.Constant(i32(constant->GetS32())); | 
 |                         }, | 
 |                         [&](const core::type::U32*) { | 
 |                             return b_.Constant(u32(constant->GetU32())); | 
 |                         }, | 
 |                         [&](const core::type::F32*) { | 
 |                             return b_.Constant(f32(constant->GetFloat())); | 
 |                         }, | 
 |                         [&](const core::type::F16*) { | 
 |                             auto bits = constant->AsScalarConstant()->GetU32BitValue(); | 
 |                             return b_.Constant(f16::FromBits(static_cast<uint16_t>(bits))); | 
 |                         }, | 
 |                         TINT_ICE_ON_NO_MATCH); | 
 |  | 
 |                     auto spec_id = GetSpecId(inst); | 
 |                     CreateOverride(inst, value, spec_id); | 
 |                     break; | 
 |                 } | 
 |                 case spv::Op::OpSpecConstantOp: { | 
 |                     auto op = inst.GetSingleWordInOperand(0); | 
 |  | 
 |                     // Store the name away and remove it from the name list. | 
 |                     // This keeps any `Emit*` call in the switch below for | 
 |                     // gaining the name we want associated to the override. | 
 |                     std::string name; | 
 |                     auto iter = id_to_name_.find(inst.result_id()); | 
 |                     if (iter != id_to_name_.end()) { | 
 |                         name = iter->second; | 
 |                         id_to_name_.erase(inst.result_id()); | 
 |                     } | 
 |  | 
 |                     switch (static_cast<spv::Op>(op)) { | 
 |                         case spv::Op::OpBitwiseAnd: | 
 |                             EmitSpirvExplicitBuiltinCall(inst, spirv::BuiltinFn::kBitwiseAnd, 3); | 
 |                             break; | 
 |                         case spv::Op::OpBitwiseOr: | 
 |                             EmitSpirvExplicitBuiltinCall(inst, spirv::BuiltinFn::kBitwiseOr, 3); | 
 |                             break; | 
 |                         case spv::Op::OpBitwiseXor: | 
 |                             EmitSpirvExplicitBuiltinCall(inst, spirv::BuiltinFn::kBitwiseXor, 3); | 
 |                             break; | 
 |                         case spv::Op::OpIEqual: | 
 |                             EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kEqual, 3); | 
 |                             break; | 
 |                         case spv::Op::OpINotEqual: | 
 |                             EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kNotEqual, 3); | 
 |                             break; | 
 |                         case spv::Op::OpSGreaterThan: | 
 |                             EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kSGreaterThan, 3); | 
 |                             break; | 
 |                         case spv::Op::OpSGreaterThanEqual: | 
 |                             EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kSGreaterThanEqual, 3); | 
 |                             break; | 
 |                         case spv::Op::OpSLessThan: | 
 |                             EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kSLessThan, 3); | 
 |                             break; | 
 |                         case spv::Op::OpSLessThanEqual: | 
 |                             EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kSLessThanEqual, 3); | 
 |                             break; | 
 |                         case spv::Op::OpUGreaterThan: | 
 |                             EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kUGreaterThan, 3); | 
 |                             break; | 
 |                         case spv::Op::OpUGreaterThanEqual: | 
 |                             EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kUGreaterThanEqual, 3); | 
 |                             break; | 
 |                         case spv::Op::OpULessThan: | 
 |                             EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kULessThan, 3); | 
 |                             break; | 
 |                         case spv::Op::OpULessThanEqual: | 
 |                             EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kULessThanEqual, 3); | 
 |                             break; | 
 |                         case spv::Op::OpLogicalAnd: | 
 |                             EmitBinary(inst, core::BinaryOp::kAnd, 3); | 
 |                             break; | 
 |                         case spv::Op::OpLogicalOr: | 
 |                             EmitBinary(inst, core::BinaryOp::kOr, 3); | 
 |                             break; | 
 |                         case spv::Op::OpLogicalNot: | 
 |                             EmitUnary(inst, core::UnaryOp::kNot, 3); | 
 |                             break; | 
 |                         case spv::Op::OpLogicalEqual: | 
 |                             EmitBinary(inst, core::BinaryOp::kEqual, 3); | 
 |                             break; | 
 |                         case spv::Op::OpLogicalNotEqual: | 
 |                             EmitBinary(inst, core::BinaryOp::kNotEqual, 3); | 
 |                             break; | 
 |                         case spv::Op::OpNot: | 
 |                             EmitSpirvExplicitBuiltinCall(inst, spirv::BuiltinFn::kNot, 3); | 
 |                             break; | 
 |                         case spv::Op::OpSConvert: | 
 |                             TINT_ICE() << "can't translate SConvert: WGSL does not have concrete " | 
 |                                           "integer types of different widths"; | 
 |                         case spv::Op::OpUConvert: | 
 |                             TINT_ICE() << "can't translate UConvert: WGSL does not have concrete " | 
 |                                           "integer types of different widths"; | 
 |                         case spv::Op::OpFConvert: | 
 |                             Emit(b_.Convert(Type(inst.type_id()), | 
 |                                             Value(inst.GetSingleWordInOperand(1))), | 
 |                                  inst.result_id()); | 
 |                             break; | 
 |                         case spv::Op::OpSNegate: | 
 |                             EmitSpirvExplicitBuiltinCall(inst, spirv::BuiltinFn::kSNegate, 3); | 
 |                             break; | 
 |                         case spv::Op::OpIAdd: | 
 |                             EmitSpirvExplicitBuiltinCall(inst, spirv::BuiltinFn::kAdd, 3); | 
 |                             break; | 
 |                         case spv::Op::OpISub: | 
 |                             EmitSpirvExplicitBuiltinCall(inst, spirv::BuiltinFn::kSub, 3); | 
 |                             break; | 
 |                         case spv::Op::OpIMul: | 
 |                             EmitSpirvExplicitBuiltinCall(inst, spirv::BuiltinFn::kMul, 3); | 
 |                             break; | 
 |                         case spv::Op::OpSDiv: | 
 |                             EmitSpirvExplicitBuiltinCall(inst, spirv::BuiltinFn::kSDiv, 3); | 
 |                             break; | 
 |                         case spv::Op::OpUDiv: | 
 |                             EmitBinary(inst, core::BinaryOp::kDivide, 3); | 
 |                             break; | 
 |                         case spv::Op::OpUMod: | 
 |                             EmitBinary(inst, core::BinaryOp::kModulo, 3); | 
 |                             break; | 
 |                         case spv::Op::OpSMod: | 
 |                         case spv::Op::OpSRem: | 
 |                             EmitSpirvExplicitBuiltinCall(inst, spirv::BuiltinFn::kSMod, 3); | 
 |                             break; | 
 |                         default: | 
 |                             TINT_ICE() << "Unknown spec constant operation: " << op; | 
 |                     } | 
 |  | 
 |                     // Restore the saved name, if any, in order to provide that | 
 |                     // name to the override. | 
 |                     if (!name.empty()) { | 
 |                         id_to_name_.insert({inst.result_id(), name}); | 
 |                     } | 
 |  | 
 |                     CreateOverride(inst, Value(inst.result_id()), std::nullopt); | 
 |                     break; | 
 |                 } | 
 |                 case spv::Op::OpSpecConstantComposite: { | 
 |                     auto spec_id = GetSpecId(inst); | 
 |                     if (spec_id.has_value()) { | 
 |                         TINT_ICE() | 
 |                             << "OpSpecConstantCompositeOp not supported when set with a SpecId"; | 
 |                     } | 
 |  | 
 |                     auto* cnst = SpvConstant(inst.result_id()); | 
 |                     if (cnst != nullptr) { | 
 |                         // The spec constant is made of literals, so it's return as a constant from | 
 |                         // SPIR-V Tools Opt. We can just ignore it and let the normal constant | 
 |                         // handling take over. | 
 |                         break; | 
 |                     } | 
 |  | 
 |                     Vector<uint32_t, 4> args; | 
 |                     args.Reserve(inst.NumInOperands()); | 
 |  | 
 |                     for (uint32_t i = 0; i < inst.NumInOperands(); ++i) { | 
 |                         uint32_t id = inst.GetSingleWordInOperand(i); | 
 |                         args.Push(id); | 
 |                     } | 
 |  | 
 |                     spec_composites_.insert({inst.result_id(), SpecComposite{ | 
 |                                                                    .type = Type(inst.type_id()), | 
 |                                                                    .args = args, | 
 |                                                                }}); | 
 |                     break; | 
 |                 } | 
 |                 default: | 
 |                     break; | 
 |             } | 
 |         } | 
 |     } | 
 |  | 
 |     void RegisterNames() { | 
 |         // Register names from OpName | 
 |         for (const auto& inst : spirv_context_->debugs2()) { | 
 |             switch (inst.opcode()) { | 
 |                 case spv::Op::OpName: { | 
 |                     const auto name = inst.GetInOperand(1).AsString(); | 
 |                     if (!name.empty()) { | 
 |                         id_to_name_[inst.GetSingleWordInOperand(0)] = name; | 
 |                     } | 
 |                     break; | 
 |                 } | 
 |                 case spv::Op::OpMemberName: { | 
 |                     const auto name = inst.GetInOperand(2).AsString(); | 
 |                     if (!name.empty()) { | 
 |                         uint32_t struct_id = inst.GetSingleWordInOperand(0); | 
 |                         uint32_t member_idx = inst.GetSingleWordInOperand(1); | 
 |                         auto iter = struct_to_member_names_.insert({struct_id, {}}); | 
 |                         auto& members = (*(iter.first)).second; | 
 |  | 
 |                         if (members.size() < (member_idx + 1)) { | 
 |                             members.resize(member_idx + 1); | 
 |                         } | 
 |                         members[member_idx] = name; | 
 |                     } | 
 |                     break; | 
 |                 } | 
 |                 default: | 
 |                     break; | 
 |             } | 
 |         } | 
 |     } | 
 |  | 
 |     /// @param sc a SPIR-V storage class | 
 |     /// @returns the Tint address space for a SPIR-V storage class | 
 |     core::AddressSpace AddressSpace(spv::StorageClass sc) { | 
 |         switch (sc) { | 
 |             case spv::StorageClass::Input: | 
 |                 return core::AddressSpace::kIn; | 
 |             case spv::StorageClass::Output: | 
 |                 return core::AddressSpace::kOut; | 
 |             case spv::StorageClass::Function: | 
 |                 return core::AddressSpace::kFunction; | 
 |             case spv::StorageClass::Private: | 
 |                 return core::AddressSpace::kPrivate; | 
 |             case spv::StorageClass::StorageBuffer: | 
 |                 return core::AddressSpace::kStorage; | 
 |             case spv::StorageClass::Uniform: | 
 |                 return core::AddressSpace::kUniform; | 
 |             case spv::StorageClass::UniformConstant: | 
 |                 return core::AddressSpace::kHandle; | 
 |             case spv::StorageClass::Workgroup: | 
 |                 return core::AddressSpace::kWorkgroup; | 
 |             default: | 
 |                 TINT_UNIMPLEMENTED() | 
 |                     << "unhandled SPIR-V storage class: " << static_cast<uint32_t>(sc); | 
 |         } | 
 |     } | 
 |  | 
 |     /// @param b a SPIR-V BuiltIn | 
 |     /// @returns the Tint builtin value for a SPIR-V BuiltIn decoration | 
 |     core::BuiltinValue Builtin(spv::BuiltIn b) { | 
 |         switch (b) { | 
 |             case spv::BuiltIn::FragCoord: | 
 |                 return core::BuiltinValue::kPosition; | 
 |             case spv::BuiltIn::FragDepth: | 
 |                 return core::BuiltinValue::kFragDepth; | 
 |             case spv::BuiltIn::FrontFacing: | 
 |                 return core::BuiltinValue::kFrontFacing; | 
 |             case spv::BuiltIn::GlobalInvocationId: | 
 |                 return core::BuiltinValue::kGlobalInvocationId; | 
 |             case spv::BuiltIn::InstanceIndex: | 
 |                 return core::BuiltinValue::kInstanceIndex; | 
 |             case spv::BuiltIn::LocalInvocationId: | 
 |                 return core::BuiltinValue::kLocalInvocationId; | 
 |             case spv::BuiltIn::LocalInvocationIndex: | 
 |                 return core::BuiltinValue::kLocalInvocationIndex; | 
 |             case spv::BuiltIn::NumWorkgroups: | 
 |                 return core::BuiltinValue::kNumWorkgroups; | 
 |             case spv::BuiltIn::PointSize: | 
 |                 return core::BuiltinValue::kPointSize; | 
 |             case spv::BuiltIn::Position: | 
 |                 return core::BuiltinValue::kPosition; | 
 |             case spv::BuiltIn::SampleId: | 
 |                 return core::BuiltinValue::kSampleIndex; | 
 |             case spv::BuiltIn::SampleMask: | 
 |                 return core::BuiltinValue::kSampleMask; | 
 |             case spv::BuiltIn::VertexIndex: | 
 |                 return core::BuiltinValue::kVertexIndex; | 
 |             case spv::BuiltIn::WorkgroupId: | 
 |                 return core::BuiltinValue::kWorkgroupId; | 
 |             case spv::BuiltIn::ClipDistance: | 
 |                 return core::BuiltinValue::kClipDistances; | 
 |             case spv::BuiltIn::CullDistance: | 
 |                 return core::BuiltinValue::kCullDistance; | 
 |             default: | 
 |                 TINT_UNIMPLEMENTED() << "unhandled SPIR-V BuiltIn: " << static_cast<uint32_t>(b); | 
 |         } | 
 |     } | 
 |  | 
 |     /// @param type a SPIR-V type object | 
 |     /// @param access_mode an optional access mode (for pointers) | 
 |     /// @returns a Tint type object | 
 |     const core::type::Type* Type(const spvtools::opt::analysis::Type* type, | 
 |                                  core::Access access_mode = core::Access::kUndefined) { | 
 |         auto key_mode = core::Access::kUndefined; | 
 |         if (type->kind() == spvtools::opt::analysis::Type::kImage) { | 
 |             key_mode = access_mode; | 
 |         } else if (type->kind() == spvtools::opt::analysis::Type::kPointer) { | 
 |             // Pointers use the access mode, unless they're handle pointers in which case they get | 
 |             // Read. | 
 |             key_mode = access_mode; | 
 |  | 
 |             auto* ptr = type->AsPointer(); | 
 |             if (ptr->pointee_type()->kind() == spvtools::opt::analysis::Type::kSampler || | 
 |                 ptr->pointee_type()->kind() == spvtools::opt::analysis::Type::kImage) { | 
 |                 key_mode = core::Access::kRead; | 
 |             } | 
 |         } | 
 |  | 
 |         return types_.GetOrAdd(TypeKey{type, key_mode}, [&]() -> const core::type::Type* { | 
 |             // TODO(crbug.com/1907): Handle decorations that affect the type | 
 |             uint32_t array_stride = 0; | 
 |             bool set_as_storage_buffer = false; | 
 |             for (auto& deco : type->decorations()) { | 
 |                 switch (spv::Decoration(deco[0])) { | 
 |                     case spv::Decoration::Block: { | 
 |                         // Ignore, just means it's a memory block. | 
 |                         break; | 
 |                     } | 
 |                     case spv::Decoration::BufferBlock: { | 
 |                         set_as_storage_buffer = true; | 
 |                         break; | 
 |                     } | 
 |                     case spv::Decoration::ArrayStride: { | 
 |                         array_stride = deco[1]; | 
 |                         break; | 
 |                     } | 
 |                     default: { | 
 |                         TINT_UNIMPLEMENTED() << " unhandled type decoration " << deco[0]; | 
 |                     } | 
 |                 } | 
 |             } | 
 |             // Storage buffer is only set ons structs | 
 |             if (set_as_storage_buffer) { | 
 |                 TINT_ASSERT(type->kind() == spvtools::opt::analysis::Type::kStruct); | 
 |             } | 
 |             // ArrayStride is only handled on the array type for now | 
 |             if (array_stride > 0) { | 
 |                 TINT_ASSERT(type->kind() == spvtools::opt::analysis::Type::kArray || | 
 |                             type->kind() == spvtools::opt::analysis::Type::kRuntimeArray); | 
 |             } | 
 |  | 
 |             switch (type->kind()) { | 
 |                 case spvtools::opt::analysis::Type::kVoid: { | 
 |                     return ty_.void_(); | 
 |                 } | 
 |                 case spvtools::opt::analysis::Type::kBool: { | 
 |                     return ty_.bool_(); | 
 |                 } | 
 |                 case spvtools::opt::analysis::Type::kInteger: { | 
 |                     auto* int_ty = type->AsInteger(); | 
 |                     TINT_ASSERT(int_ty->width() == 32); | 
 |                     if (int_ty->IsSigned()) { | 
 |                         return ty_.i32(); | 
 |                     } else { | 
 |                         return ty_.u32(); | 
 |                     } | 
 |                 } | 
 |                 case spvtools::opt::analysis::Type::kFloat: { | 
 |                     auto* float_ty = type->AsFloat(); | 
 |                     if (float_ty->width() == 16) { | 
 |                         return ty_.f16(); | 
 |                     } else if (float_ty->width() == 32) { | 
 |                         return ty_.f32(); | 
 |                     } else { | 
 |                         TINT_UNREACHABLE() | 
 |                             << "unsupported floating point type width: " << float_ty->width(); | 
 |                     } | 
 |                 } | 
 |                 case spvtools::opt::analysis::Type::kVector: { | 
 |                     auto* vec_ty = type->AsVector(); | 
 |                     TINT_ASSERT(vec_ty->element_count() <= 4); | 
 |                     return ty_.vec(Type(vec_ty->element_type()), vec_ty->element_count()); | 
 |                 } | 
 |                 case spvtools::opt::analysis::Type::kMatrix: { | 
 |                     auto* mat_ty = type->AsMatrix(); | 
 |                     TINT_ASSERT(mat_ty->element_count() <= 4); | 
 |                     return ty_.mat(As<core::type::Vector>(Type(mat_ty->element_type())), | 
 |                                    mat_ty->element_count()); | 
 |                 } | 
 |                 case spvtools::opt::analysis::Type::kArray: { | 
 |                     return EmitArray(type->AsArray(), array_stride); | 
 |                 } | 
 |                 case spvtools::opt::analysis::Type::kRuntimeArray: { | 
 |                     auto* arr_ty = type->AsRuntimeArray(); | 
 |  | 
 |                     auto* elem_ty = Type(arr_ty->element_type()); | 
 |                     uint32_t implicit_stride = tint::RoundUp(elem_ty->Align(), elem_ty->Size()); | 
 |                     if (array_stride == 0 || array_stride == implicit_stride) { | 
 |                         return ty_.runtime_array(elem_ty); | 
 |                     } | 
 |  | 
 |                     return ty_.Get<spirv::type::ExplicitLayoutArray>( | 
 |                         elem_ty, ty_.Get<core::type::RuntimeArrayCount>(), elem_ty->Align(), | 
 |                         static_cast<uint32_t>(array_stride), array_stride); | 
 |                 } | 
 |                 case spvtools::opt::analysis::Type::kStruct: { | 
 |                     const core::type::Struct* str_ty = EmitStruct(type->AsStruct()); | 
 |                     if (set_as_storage_buffer) { | 
 |                         storage_buffer_types_.insert(str_ty); | 
 |                     } | 
 |                     return str_ty; | 
 |                 } | 
 |                 case spvtools::opt::analysis::Type::kPointer: { | 
 |                     auto* ptr_ty = type->AsPointer(); | 
 |                     auto* subtype = Type(ptr_ty->pointee_type(), access_mode); | 
 |                     // Handle is always a read pointer | 
 |                     if (subtype->IsHandle()) { | 
 |                         access_mode = core::Access::kRead; | 
 |                     } | 
 |                     return ty_.ptr(AddressSpace(ptr_ty->storage_class()), subtype, access_mode); | 
 |                 } | 
 |                 case spvtools::opt::analysis::Type::kSampler: { | 
 |                     return ty_.sampler(); | 
 |                 } | 
 |                 case spvtools::opt::analysis::Type::kImage: { | 
 |                     auto* img = type->AsImage(); | 
 |  | 
 |                     auto* sampled_ty = Type(img->sampled_type()); | 
 |                     auto dim = static_cast<type::Dim>(img->dim()); | 
 |                     auto depth = static_cast<type::Depth>(img->depth()); | 
 |                     auto arrayed = | 
 |                         img->is_arrayed() ? type::Arrayed::kArrayed : type::Arrayed::kNonArrayed; | 
 |                     auto ms = img->is_multisampled() ? type::Multisampled::kMultisampled | 
 |                                                      : type::Multisampled::kSingleSampled; | 
 |                     auto sampled = static_cast<type::Sampled>(img->sampled()); | 
 |                     auto texel_format = ToTexelFormat(img->format()); | 
 |  | 
 |                     // If the access mode is undefined then default to read/write for the image | 
 |                     access_mode = access_mode == core::Access::kUndefined ? core::Access::kReadWrite | 
 |                                                                           : access_mode; | 
 |  | 
 |                     if (img->dim() != spv::Dim::Dim1D && img->dim() != spv::Dim::Dim2D && | 
 |                         img->dim() != spv::Dim::Dim3D && img->dim() != spv::Dim::Cube && | 
 |                         img->dim() != spv::Dim::SubpassData) { | 
 |                         TINT_ICE() << "Unsupported texture dimension: " | 
 |                                    << static_cast<uint32_t>(img->dim()); | 
 |                     } | 
 |                     if (img->sampled() == 0) { | 
 |                         TINT_ICE() << "Unsupported texture sample setting: Known at Runtime"; | 
 |                     } | 
 |  | 
 |                     return ty_.Get<spirv::type::Image>(sampled_ty, dim, depth, arrayed, ms, sampled, | 
 |                                                        texel_format, access_mode); | 
 |                 } | 
 |                 case spvtools::opt::analysis::Type::kSampledImage: { | 
 |                     auto* sampled = type->AsSampledImage(); | 
 |                     return ty_.Get<spirv::type::SampledImage>(Type(sampled->image_type())); | 
 |                 } | 
 |                 default: { | 
 |                     TINT_UNIMPLEMENTED() << "unhandled SPIR-V type: " << type->str(); | 
 |                 } | 
 |             } | 
 |         }); | 
 |     } | 
 |  | 
 |     core::TexelFormat ToTexelFormat(spv::ImageFormat fmt) { | 
 |         switch (fmt) { | 
 |             case spv::ImageFormat::Unknown: | 
 |                 return core::TexelFormat::kUndefined; | 
 |  | 
 |             // 8 bit channels | 
 |             case spv::ImageFormat::Rgba8: | 
 |                 return core::TexelFormat::kRgba8Unorm; | 
 |             case spv::ImageFormat::Rgba8Snorm: | 
 |                 return core::TexelFormat::kRgba8Snorm; | 
 |             case spv::ImageFormat::Rgba8ui: | 
 |                 return core::TexelFormat::kRgba8Uint; | 
 |             case spv::ImageFormat::Rgba8i: | 
 |                 return core::TexelFormat::kRgba8Sint; | 
 |  | 
 |             // 16 bit channels | 
 |             case spv::ImageFormat::Rgba16ui: | 
 |                 return core::TexelFormat::kRgba16Uint; | 
 |             case spv::ImageFormat::Rgba16i: | 
 |                 return core::TexelFormat::kRgba16Sint; | 
 |             case spv::ImageFormat::Rgba16f: | 
 |                 return core::TexelFormat::kRgba16Float; | 
 |  | 
 |             // 32 bit channels | 
 |             case spv::ImageFormat::R32ui: | 
 |                 return core::TexelFormat::kR32Uint; | 
 |             case spv::ImageFormat::R32i: | 
 |                 return core::TexelFormat::kR32Sint; | 
 |             case spv::ImageFormat::R32f: | 
 |                 return core::TexelFormat::kR32Float; | 
 |             case spv::ImageFormat::Rg32ui: | 
 |                 return core::TexelFormat::kRg32Uint; | 
 |             case spv::ImageFormat::Rg32i: | 
 |                 return core::TexelFormat::kRg32Sint; | 
 |             case spv::ImageFormat::Rg32f: | 
 |                 return core::TexelFormat::kRg32Float; | 
 |             case spv::ImageFormat::Rgba32ui: | 
 |                 return core::TexelFormat::kRgba32Uint; | 
 |             case spv::ImageFormat::Rgba32i: | 
 |                 return core::TexelFormat::kRgba32Sint; | 
 |             case spv::ImageFormat::Rgba32f: | 
 |                 return core::TexelFormat::kRgba32Float; | 
 |             default: | 
 |                 break; | 
 |         } | 
 |         TINT_ICE() << "invalid image format: " << int(fmt); | 
 |     } | 
 |  | 
 |     /// @param id a SPIR-V result ID for a type declaration instruction | 
 |     /// @param access_mode an optional access mode (for pointers) | 
 |     /// @returns a Tint type object | 
 |     const core::type::Type* Type(uint32_t id, core::Access access_mode = core::Access::kUndefined) { | 
 |         return Type(spirv_context_->get_type_mgr()->GetType(id), access_mode); | 
 |     } | 
 |  | 
 |     /// @param arr_ty a SPIR-V array object | 
 |     /// @returns a Tint array object | 
 |     const core::type::Type* EmitArray(const spvtools::opt::analysis::Array* arr_ty, | 
 |                                       uint32_t array_stride) { | 
 |         const auto& length = arr_ty->length_info(); | 
 |         TINT_ASSERT(!length.words.empty()); | 
 |         if (length.words[0] != spvtools::opt::analysis::Array::LengthInfo::kConstant) { | 
 |             TINT_UNIMPLEMENTED() << "specialized array lengths"; | 
 |         } | 
 |  | 
 |         // Get the value from the constant used for the element count. | 
 |         const auto* count_const = | 
 |             spirv_context_->get_constant_mgr()->FindDeclaredConstant(length.id); | 
 |         TINT_ASSERT(count_const); | 
 |         const uint64_t count_val = count_const->GetZeroExtendedValue(); | 
 |         TINT_ASSERT(count_val <= UINT32_MAX); | 
 |  | 
 |         auto* elem_ty = Type(arr_ty->element_type()); | 
 |         uint32_t implicit_stride = tint::RoundUp(elem_ty->Align(), elem_ty->Size()); | 
 |         if (array_stride == 0 || array_stride == implicit_stride) { | 
 |             return ty_.array(elem_ty, static_cast<uint32_t>(count_val)); | 
 |         } | 
 |  | 
 |         return ty_.Get<spirv::type::ExplicitLayoutArray>( | 
 |             elem_ty, ty_.Get<core::type::ConstantArrayCount>(static_cast<uint32_t>(count_val)), | 
 |             elem_ty->Align(), static_cast<uint32_t>(array_stride * count_val), array_stride); | 
 |     } | 
 |  | 
 |     /// @param struct_ty a SPIR-V struct object | 
 |     /// @returns a Tint struct object | 
 |     const core::type::Struct* EmitStruct(const spvtools::opt::analysis::Struct* struct_ty) { | 
 |         if (struct_ty->NumberOfComponents() == 0) { | 
 |             TINT_ICE() << "empty structures are not supported"; | 
 |         } | 
 |  | 
 |         auto* type_mgr = spirv_context_->get_type_mgr(); | 
 |         auto struct_id = type_mgr->GetId(struct_ty); | 
 |  | 
 |         std::vector<std::string>* member_names = nullptr; | 
 |         auto struct_to_member_iter = struct_to_member_names_.find(struct_id); | 
 |         if (struct_to_member_iter != struct_to_member_names_.end()) { | 
 |             member_names = &((*struct_to_member_iter).second); | 
 |         } | 
 |  | 
 |         // Build a list of struct members. | 
 |         uint32_t current_size = 0u; | 
 |         Vector<core::type::StructMember*, 4> members; | 
 |         for (uint32_t i = 0; i < struct_ty->NumberOfComponents(); i++) { | 
 |             auto* member_ty = Type(struct_ty->element_types()[i]); | 
 |             uint32_t align = std::max<uint32_t>(member_ty->Align(), 1u); | 
 |             uint32_t offset = tint::RoundUp(align, current_size); | 
 |             core::IOAttributes attributes; | 
 |             auto interpolation = [&]() -> core::Interpolation& { | 
 |                 // Create the interpolation field with the default values on first call. | 
 |                 if (!attributes.interpolation.has_value()) { | 
 |                     attributes.interpolation = | 
 |                         core::Interpolation{core::InterpolationType::kPerspective, | 
 |                                             core::InterpolationSampling::kUndefined}; | 
 |                 } | 
 |                 return attributes.interpolation.value(); | 
 |             }; | 
 |  | 
 |             bool is_row_major = false; | 
 |             uint32_t matrix_stride = 0; | 
 |             // Handle member decorations that affect layout or attributes. | 
 |             if (struct_ty->element_decorations().count(i)) { | 
 |                 for (auto& deco : struct_ty->element_decorations().at(i)) { | 
 |                     switch (spv::Decoration(deco[0])) { | 
 |                         case spv::Decoration::ColMajor:          // Do nothing, WGSL is column major | 
 |                         case spv::Decoration::NonReadable:       // Not supported in WGSL | 
 |                         case spv::Decoration::NonWritable:       // Not supported in WGSL | 
 |                         case spv::Decoration::RelaxedPrecision:  // Not supported in WGSL | 
 |                             break; | 
 |                         case spv::Decoration::RowMajor: | 
 |                             is_row_major = true; | 
 |                             break; | 
 |                         case spv::Decoration::MatrixStride: | 
 |                             matrix_stride = deco[1]; | 
 |                             break; | 
 |                         case spv::Decoration::Offset: | 
 |                             offset = deco[1]; | 
 |                             break; | 
 |                         case spv::Decoration::BuiltIn: | 
 |                             attributes.builtin = Builtin(spv::BuiltIn(deco[1])); | 
 |                             break; | 
 |                         case spv::Decoration::Invariant: | 
 |                             attributes.invariant = true; | 
 |                             break; | 
 |                         case spv::Decoration::Location: | 
 |                             attributes.location = deco[1]; | 
 |                             break; | 
 |                         case spv::Decoration::NoPerspective: | 
 |                             interpolation().type = core::InterpolationType::kLinear; | 
 |                             break; | 
 |                         case spv::Decoration::Flat: | 
 |                             interpolation().type = core::InterpolationType::kFlat; | 
 |                             break; | 
 |                         case spv::Decoration::Centroid: | 
 |                             interpolation().sampling = core::InterpolationSampling::kCentroid; | 
 |                             break; | 
 |                         case spv::Decoration::Sample: | 
 |                             interpolation().sampling = core::InterpolationSampling::kSample; | 
 |                             break; | 
 |  | 
 |                         default: | 
 |                             TINT_UNIMPLEMENTED() << "unhandled member decoration: " << deco[0]; | 
 |                     } | 
 |                 } | 
 |             } | 
 |  | 
 |             Symbol name; | 
 |             if (member_names && member_names->size() > i) { | 
 |                 auto n = (*member_names)[i]; | 
 |                 if (!n.empty()) { | 
 |                     name = ir_.symbols.Register(n); | 
 |                 } | 
 |             } | 
 |             if (!name.IsValid()) { | 
 |                 name = ir_.symbols.New(); | 
 |             } | 
 |  | 
 |             core::type::StructMember* member = ty_.Get<core::type::StructMember>( | 
 |                 name, member_ty, i, offset, align, member_ty->Size(), std::move(attributes)); | 
 |             if (is_row_major) { | 
 |                 member->SetRowMajor(); | 
 |             } | 
 |             if (matrix_stride > 0) { | 
 |                 member->SetMatrixStride(matrix_stride); | 
 |             } | 
 |  | 
 |             members.Push(member); | 
 |  | 
 |             current_size = offset + member_ty->Size(); | 
 |         } | 
 |  | 
 |         Symbol name = GetUniqueSymbolFor(struct_id); | 
 |         if (!name.IsValid()) { | 
 |             name = ir_.symbols.New(); | 
 |         } | 
 |         return ty_.Struct(name, std::move(members)); | 
 |     } | 
 |  | 
 |     Symbol GetUniqueSymbolFor(uint32_t id) { | 
 |         auto iter = id_to_name_.find(id); | 
 |         if (iter != id_to_name_.end()) { | 
 |             return ir_.symbols.New(iter->second); | 
 |         } | 
 |         return Symbol{}; | 
 |     } | 
 |  | 
 |     Symbol GetSymbolFor(uint32_t id) { | 
 |         auto iter = id_to_name_.find(id); | 
 |         if (iter != id_to_name_.end()) { | 
 |             return ir_.symbols.Register(iter->second); | 
 |         } | 
 |         return Symbol{}; | 
 |     } | 
 |  | 
 |     /// @param id a SPIR-V result ID for a function declaration instruction | 
 |     /// @returns a Tint function object | 
 |     core::ir::Function* Function(uint32_t id) { | 
 |         return functions_.GetOrAdd(id, [&] { return b_.Function(ty_.void_()); }); | 
 |     } | 
 |  | 
 |     // Passes a value up through control flow to make it visible in an outer scope. Because SPIR-V | 
 |     // allows an id to be referenced as long as it's dominated, you can access a variable which is | 
 |     // defined inside an if branch for example. In order for that to be accessed in IR, we have to | 
 |     // propagate the value as a return of the control instruction (like the if). | 
 |     // | 
 |     // e.g. if the IR is similar to the following: | 
 |     // ``` | 
 |     // if (b) { | 
 |     //    %a:i32 = let 4; | 
 |     //    exit_if | 
 |     // } | 
 |     // %c:i32 = %a + %a; | 
 |     // ``` | 
 |     // | 
 |     // We propagate to something like: | 
 |     // ``` | 
 |     // %d:i32 = if (b) { | 
 |     //   %a:i32 = let 4;  // The spir-v ID refers to %a at this point | 
 |     //   exit_if %a | 
 |     // } | 
 |     // %c:i32 = %d + %d  // The spir-v ID will now refer to %d instead of %a | 
 |     // ``` | 
 |     // | 
 |     // We can end up propagating up through multiple levels, so we can end up with something like: | 
 |     // ``` | 
 |     // %k:i32 = if (true) { | 
 |     //   %l:i32 = if (false) { | 
 |     //     %m:i32 = if (true) { | 
 |     //       %n:i32 = switch 4 { | 
 |     //         default: { | 
 |     //           %o:i32 = loop { | 
 |     //             %a:i32 = let 4; | 
 |     //             exit_loop %a | 
 |     //           } | 
 |     //           exit_switch %o | 
 |     //         } | 
 |     //       } | 
 |     //       exit_if %n | 
 |     //     } | 
 |     //     exit_if %m | 
 |     //   } | 
 |     //   exit_if %l | 
 |     // } | 
 |     // %b:i32 = %k + %k | 
 |     // ``` | 
 |     // | 
 |     // @param id the spir-v ID to propagate up | 
 |     // @param src the source value being propagated | 
 |     core::ir::Value* Propagate(uint32_t id, core::ir::Value* src) { | 
 |         // Function params are always in scope so we should never need to propagate. | 
 |         if (src->Is<core::ir::FunctionParam>()) { | 
 |             return src; | 
 |         } | 
 |  | 
 |         auto* blk = tint::Switch( | 
 |             src,  // | 
 |             [&](core::ir::BlockParam* bp) { return bp->Block(); }, | 
 |             [&](core::ir::InstructionResult* res) { return res->Instruction()->Block(); }, | 
 |             TINT_ICE_ON_NO_MATCH); | 
 |  | 
 |         // Walk up the set of control instructions from the current `blk`. We'll update the `src` | 
 |         // instruction as the new result which is to be used for the given SPIR-V `id`. At each | 
 |         // control instruction we'll add the current `src` as a result of each exit from the control | 
 |         // instruction, making a new result which is available in the parent scope. | 
 |         while (blk) { | 
 |             if (InBlock(blk)) { | 
 |                 break; | 
 |             } | 
 |  | 
 |             core::ir::ControlInstruction* ctrl = nullptr; | 
 |             if (auto* mb = blk->As<core::ir::MultiInBlock>()) { | 
 |                 ctrl = mb->Parent()->As<core::ir::ControlInstruction>(); | 
 |                 TINT_ASSERT(ctrl); | 
 |  | 
 |                 for (auto exit : ctrl->Exits()) { | 
 |                     tint::Switch( | 
 |                         exit.Value(),  // | 
 |                         [&](core::ir::ExitLoop* el) { el->PushOperand(src); }, | 
 |                         [&](core::ir::BreakIf* bi) { bi->PushOperand(src); },  // | 
 |                         TINT_ICE_ON_NO_MATCH); | 
 |                 } | 
 |             } else { | 
 |                 TINT_ASSERT(blk->Terminator()); | 
 |  | 
 |                 ctrl = tint::Switch( | 
 |                     blk->Terminator(),  // | 
 |                     [&](core::ir::ExitIf* ei) { return ei->If(); }, | 
 |                     [&](core::ir::ExitSwitch* es) { return es->Switch(); }, | 
 |                     [&](core::ir::ExitLoop* el) { return el->Loop(); }, | 
 |                     [&](core::ir::NextIteration* ni) { return ni->Loop(); }, | 
 |                     [&](core::ir::Continue* cont) { | 
 |                         // The propagation is going through a `continue`. This means | 
 |                         // this is the only path to the continuing block, but it also | 
 |                         // means we're current in the continuing block. We can't do | 
 |                         // normal propagation here, we have to pass a block param | 
 |                         // instead. | 
 |  | 
 |                         auto* param = b_.BlockParam(src->Type()); | 
 |  | 
 |                         // We're in the continuing block, so make the block param available in the | 
 |                         // scope. | 
 |                         id_stack_.back().insert(id); | 
 |  | 
 |                         auto* loop = cont->Loop(); | 
 |                         loop->Continuing()->AddParam(param); | 
 |  | 
 |                         cont->PushOperand(src); | 
 |  | 
 |                         // Set `src` as the `param` so it's returned as the new value | 
 |                         src = param; | 
 |                         return nullptr; | 
 |                     },                                                      // | 
 |                     [&](core::ir::Unreachable*) { return blk->Parent(); },  // | 
 |                     TINT_ICE_ON_NO_MATCH); | 
 |  | 
 |                 if (!ctrl) { | 
 |                     break; | 
 |                 } | 
 |  | 
 |                 for (auto& exit : ctrl->Exits()) { | 
 |                     exit->PushOperand(src); | 
 |                 } | 
 |             } | 
 |  | 
 |             // If this control has no exits, then we don't need to add the result through the | 
 |             // control as we're jumping over the control to its parent control. (This is an | 
 |             // `if` inside a `loop` where the `if` is doing a `break`). | 
 |             if (ctrl->Exits().IsEmpty()) { | 
 |                 TINT_ASSERT(ctrl->Is<core::ir::If>()); | 
 |                 blk = ctrl->Block(); | 
 |                 continue; | 
 |             } | 
 |  | 
 |             // Add a new result to the control instruction | 
 |             ctrl->AddResult(b_.InstructionResult(src->Type())); | 
 |             // The source instruction is now the control result we just inserted | 
 |             src = ctrl->Results().Back(); | 
 |             // The SPIR-V ID now refers to the propagated value. | 
 |             values_.Replace(id, src); | 
 |  | 
 |             blk = ctrl->Block(); | 
 |         } | 
 |         return src; | 
 |     } | 
 |  | 
 |     bool IdIsInScope(uint32_t id) { | 
 |         for (auto iter = id_stack_.rbegin(); iter != id_stack_.rend(); ++iter) { | 
 |             if (iter->count(id) > 0) { | 
 |                 return true; | 
 |             } | 
 |         } | 
 |         return false; | 
 |     } | 
 |  | 
 |     // Get the spirv constant for the given `id`. `nullptr` if no constant exists. | 
 |     const spvtools::opt::analysis::Constant* SpvConstant(uint32_t id) { | 
 |         return spirv_context_->get_constant_mgr()->FindDeclaredConstant(id); | 
 |     } | 
 |  | 
 |     /// Attempts to retrieve the current Tint IR value for `id`. This ignores scoping for the | 
 |     /// variable, if it exists it's returned (or if it's constant it's created). The value will not | 
 |     /// propagate up through control instructions. | 
 |     /// | 
 |     /// @param id a SPIR-V result ID | 
 |     /// @returns a Tint value object | 
 |     core::ir::Value* ValueNoPropagate(uint32_t id) { | 
 |         auto v = values_.Get(id); | 
 |         if (v) { | 
 |             return *v; | 
 |         } | 
 |  | 
 |         if (auto* c = SpvConstant(id)) { | 
 |             auto* val = b_.Constant(Constant(c)); | 
 |             values_.Add(id, val); | 
 |             return val; | 
 |         } | 
 |  | 
 |         // If this was a spec composite, then it currently isn't in scope, so we construct | 
 |         // a new copy and assign the constant ID to the new construct in this scope. | 
 |         auto iter = spec_composites_.find(id); | 
 |         if (iter != spec_composites_.end()) { | 
 |             Vector<core::ir::Value*, 4> args; | 
 |             for (auto arg : iter->second.args) { | 
 |                 args.Push(Value(arg)); | 
 |             } | 
 |  | 
 |             auto* construct = b_.Construct(iter->second.type, args); | 
 |             current_block_->Append(construct); | 
 |             values_.Replace(id, construct->Result()); | 
 |             return construct->Result(); | 
 |         } | 
 |  | 
 |         TINT_UNREACHABLE() << "missing value for result ID " << id; | 
 |     } | 
 |  | 
 |     /// Attempts to retrieve the current Tint IR value for `id`. If the value exists and is not in | 
 |     /// scope it will propagate the value up through the control instructions. | 
 |     /// | 
 |     /// @param id a SPIR-V result ID | 
 |     /// @returns a Tint value object | 
 |     core::ir::Value* Value(uint32_t id) { | 
 |         auto v = ValueNoPropagate(id); | 
 |         TINT_ASSERT(v); | 
 |  | 
 |         if (v->Is<core::ir::Constant>() || IdIsInScope(id)) { | 
 |             return v; | 
 |         } | 
 |  | 
 |         auto* new_v = Propagate(id, v); | 
 |         values_.Replace(id, new_v); | 
 |         return new_v; | 
 |     } | 
 |  | 
 |     /// Creates the Tint IR constant for the SPIR-V `constant` value. | 
 |     /// | 
 |     /// @param constant a SPIR-V constant object | 
 |     /// @returns a Tint constant value | 
 |     const core::constant::Value* Constant(const spvtools::opt::analysis::Constant* constant) { | 
 |         // Handle OpConstantNull for all types. | 
 |         if (constant->AsNullConstant()) { | 
 |             return ir_.constant_values.Zero(Type(constant->type())); | 
 |         } | 
 |  | 
 |         if (auto* bool_ = constant->AsBoolConstant()) { | 
 |             return b_.ConstantValue(bool_->value()); | 
 |         } | 
 |         if (auto* i = constant->AsIntConstant()) { | 
 |             auto* int_ty = i->type()->AsInteger(); | 
 |             TINT_ASSERT(int_ty->width() == 32); | 
 |             if (int_ty->IsSigned()) { | 
 |                 return b_.ConstantValue(i32(i->GetS32BitValue())); | 
 |             } else { | 
 |                 return b_.ConstantValue(u32(i->GetU32BitValue())); | 
 |             } | 
 |         } | 
 |         if (auto* f = constant->AsFloatConstant()) { | 
 |             auto* float_ty = f->type()->AsFloat(); | 
 |             if (float_ty->width() == 16) { | 
 |                 return b_.ConstantValue(f16::FromBits(static_cast<uint16_t>(f->words()[0]))); | 
 |             } else if (float_ty->width() == 32) { | 
 |                 return b_.ConstantValue(f32(f->GetFloat())); | 
 |             } else { | 
 |                 TINT_UNREACHABLE() << "unsupported floating point type width"; | 
 |             } | 
 |         } | 
 |         if (auto* v = constant->AsVectorConstant()) { | 
 |             Vector<const core::constant::Value*, 4> elements; | 
 |             for (auto& el : v->GetComponents()) { | 
 |                 elements.Push(Constant(el)); | 
 |             } | 
 |             return ir_.constant_values.Composite(Type(v->type()), std::move(elements)); | 
 |         } | 
 |         if (auto* m = constant->AsMatrixConstant()) { | 
 |             Vector<const core::constant::Value*, 4> columns; | 
 |             for (auto& el : m->GetComponents()) { | 
 |                 columns.Push(Constant(el)); | 
 |             } | 
 |             return ir_.constant_values.Composite(Type(m->type()), std::move(columns)); | 
 |         } | 
 |         if (auto* a = constant->AsArrayConstant()) { | 
 |             Vector<const core::constant::Value*, 16> elements; | 
 |             for (auto& el : a->GetComponents()) { | 
 |                 elements.Push(Constant(el)); | 
 |             } | 
 |             return ir_.constant_values.Composite(Type(a->type()), std::move(elements)); | 
 |         } | 
 |         if (auto* s = constant->AsStructConstant()) { | 
 |             Vector<const core::constant::Value*, 16> elements; | 
 |             for (auto& el : s->GetComponents()) { | 
 |                 elements.Push(Constant(el)); | 
 |             } | 
 |             return ir_.constant_values.Composite(Type(s->type()), std::move(elements)); | 
 |         } | 
 |         TINT_UNIMPLEMENTED() << "unhandled constant type"; | 
 |     } | 
 |  | 
 |     /// Register an IR value for a SPIR-V result ID. | 
 |     /// @param result_id the SPIR-V result ID | 
 |     /// @param value the IR value | 
 |     void AddValue(uint32_t result_id, core::ir::Value* value) { | 
 |         id_stack_.back().insert(result_id); | 
 |         values_.Replace(result_id, value); | 
 |     } | 
 |  | 
 |     /// Emit an instruction to the current block and associates the result to | 
 |     /// the spirv result id. | 
 |     /// @param inst the instruction to emit | 
 |     /// @param result_id the SPIR-V result ID to register the instruction result for | 
 |     void Emit(core::ir::Instruction* inst, uint32_t result_id) { | 
 |         current_block_->Append(inst); | 
 |         TINT_ASSERT(inst->Results().Length() == 1u); | 
 |         AddValue(result_id, inst->Result()); | 
 |  | 
 |         Symbol name = GetSymbolFor(result_id); | 
 |         if (name.IsValid()) { | 
 |             ir_.SetName(inst, name); | 
 |         } | 
 |     } | 
 |  | 
 |     /// Emit an instruction to the current block. | 
 |     /// @param inst the instruction to emit | 
 |     void EmitWithoutSpvResult(core::ir::Instruction* inst) { | 
 |         current_block_->Append(inst); | 
 |         TINT_ASSERT(inst->Results().Length() == 1u); | 
 |     } | 
 |  | 
 |     /// Emit an instruction to the current block. | 
 |     /// @param inst the instruction to emit | 
 |     void EmitWithoutResult(core::ir::Instruction* inst) { | 
 |         TINT_ASSERT(inst->Results().IsEmpty()); | 
 |         current_block_->Append(inst); | 
 |     } | 
 |  | 
 |     /// Emit the module-scope variables. | 
 |     void EmitModuleScopeVariables() { | 
 |         for (auto& inst : spirv_context_->module()->types_values()) { | 
 |             switch (inst.opcode()) { | 
 |                 case spv::Op::OpVariable: | 
 |                     EmitVar(inst); | 
 |                     break; | 
 |                 case spv::Op::OpUndef: | 
 |                     AddValue(inst.result_id(), b_.Zero(Type(inst.type_id()))); | 
 |                     break; | 
 |                 default: | 
 |                     break; | 
 |             } | 
 |         } | 
 |     } | 
 |  | 
 |     /// Emit the functions. | 
 |     void EmitFunctions() { | 
 |         // Add all the functions in a first pass and then fill in the function bodies. This means | 
 |         // the function will exist fixing an issues where calling a function that hasn't been seen | 
 |         // generates the wrong signature. | 
 |         for (auto& func : *spirv_context_->module()) { | 
 |             current_spirv_function_ = &func; | 
 |  | 
 |             Vector<core::ir::FunctionParam*, 4> params; | 
 |             func.ForEachParam([&](spvtools::opt::Instruction* spirv_param) { | 
 |                 auto* param = b_.FunctionParam(Type(spirv_param->type_id())); | 
 |                 values_.Add(spirv_param->result_id(), param); | 
 |  | 
 |                 Symbol name = GetSymbolFor(spirv_param->result_id()); | 
 |                 if (name.IsValid()) { | 
 |                     ir_.SetName(param, name); | 
 |                 } | 
 |  | 
 |                 params.Push(param); | 
 |             }); | 
 |  | 
 |             current_function_ = Function(func.result_id()); | 
 |             current_function_->SetParams(std::move(params)); | 
 |             current_function_->SetReturnType(Type(func.type_id())); | 
 |  | 
 |             Symbol name = GetSymbolFor(func.result_id()); | 
 |             if (name.IsValid()) { | 
 |                 ir_.SetName(current_function_, name); | 
 |             } | 
 |  | 
 |             functions_.Add(func.result_id(), current_function_); | 
 |             current_spirv_function_ = nullptr; | 
 |         } | 
 |  | 
 |         for (auto& func : *spirv_context_->module()) { | 
 |             current_spirv_function_ = &func; | 
 |  | 
 |             current_function_ = Function(func.result_id()); | 
 |             EmitBlockParent(current_function_->Block(), *func.entry()); | 
 |  | 
 |             // No terminator was emitted, that means then end of block is | 
 |             // unreachable. Mark as such. | 
 |             if (!current_function_->Block()->Terminator()) { | 
 |                 current_function_->Block()->Append(b_.Unreachable()); | 
 |             } | 
 |             current_spirv_function_ = nullptr; | 
 |         } | 
 |     } | 
 |  | 
 |     /// Emit entry point attributes. | 
 |     void EmitEntryPointAttributes() { | 
 |         // Handle OpEntryPoint declarations. | 
 |         for (auto& entry_point : spirv_context_->module()->entry_points()) { | 
 |             auto model = entry_point.GetSingleWordInOperand(0); | 
 |             auto* func = Function(entry_point.GetSingleWordInOperand(1)); | 
 |  | 
 |             // Set the pipeline stage. | 
 |             switch (spv::ExecutionModel(model)) { | 
 |                 case spv::ExecutionModel::GLCompute: | 
 |                     func->SetStage(core::ir::Function::PipelineStage::kCompute); | 
 |                     break; | 
 |                 case spv::ExecutionModel::Fragment: | 
 |                     func->SetStage(core::ir::Function::PipelineStage::kFragment); | 
 |                     break; | 
 |                 case spv::ExecutionModel::Vertex: | 
 |                     func->SetStage(core::ir::Function::PipelineStage::kVertex); | 
 |                     break; | 
 |                 default: | 
 |                     TINT_UNIMPLEMENTED() << "unhandled execution model: " << model; | 
 |             } | 
 |  | 
 |             // Set the entry point name. | 
 |             ir_.SetName(func, entry_point.GetOperand(2).AsString()); | 
 |  | 
 |             if (func->IsCompute()) { | 
 |                 // Search for `WorkgroupSize` decorated Ids | 
 |                 for (const spvtools::opt::Instruction& inst : | 
 |                      spirv_context_->module()->annotations()) { | 
 |                     if (inst.opcode() != spv::Op::OpDecorate || | 
 |                         inst.GetSingleWordInOperand(1) != uint32_t(spv::Decoration::BuiltIn) || | 
 |                         inst.GetSingleWordInOperand(2) != uint32_t(spv::BuiltIn::WorkgroupSize)) { | 
 |                         continue; | 
 |                     } | 
 |                     uint32_t id = inst.GetSingleWordInOperand(0); | 
 |  | 
 |                     Vector<core::ir::Value*, 3> args; | 
 |                     if (auto* c = SpvConstant(id)) { | 
 |                         auto* vals = c->AsVectorConstant(); | 
 |                         TINT_ASSERT(vals); | 
 |  | 
 |                         for (auto& el : vals->GetComponents()) { | 
 |                             args.Push(b_.Constant(Constant(el))); | 
 |                         } | 
 |                     } else { | 
 |                         TINT_ASSERT(spec_composites_.contains(id)); | 
 |  | 
 |                         auto info = spec_composites_[id]; | 
 |                         TINT_ASSERT(info.args.Length() == 3); | 
 |  | 
 |                         for (auto arg : info.args) { | 
 |                             args.Push(Value(arg)); | 
 |                         } | 
 |                     } | 
 |                     func->SetWorkgroupSize(args[0], args[1], args[2]); | 
 |  | 
 |                     break; | 
 |                 } | 
 |             } | 
 |         } | 
 |  | 
 |         // Handle OpExecutionMode declarations. | 
 |         for (auto& execution_mode : spirv_context_->module()->execution_modes()) { | 
 |             auto* func = functions_.GetOr(execution_mode.GetSingleWordInOperand(0), nullptr); | 
 |             auto mode = execution_mode.GetSingleWordInOperand(1); | 
 |             TINT_ASSERT(func); | 
 |  | 
 |             switch (spv::ExecutionMode(mode)) { | 
 |                 case spv::ExecutionMode::LocalSize: | 
 |                     func->SetWorkgroupSize( | 
 |                         b_.Constant(u32(execution_mode.GetSingleWordInOperand(2))), | 
 |                         b_.Constant(u32(execution_mode.GetSingleWordInOperand(3))), | 
 |                         b_.Constant(u32(execution_mode.GetSingleWordInOperand(4)))); | 
 |                     break; | 
 |                 case spv::ExecutionMode::DepthReplacing: | 
 |                 case spv::ExecutionMode::OriginUpperLeft: | 
 |                     // These are ignored as they are implicitly supported by Tint IR. | 
 |                     break; | 
 |                 default: | 
 |                     TINT_UNIMPLEMENTED() << "unhandled execution mode: " << mode; | 
 |             } | 
 |         } | 
 |     } | 
 |  | 
 |     bool InBlock(core::ir::Block* blk) { return current_blocks_.contains(blk); } | 
 |  | 
 |     // A block parent is a container for a scope, like a `{}`d section in code. It controls the | 
 |     // block addition to the current blocks and the ID stack entry for the block. | 
 |     void EmitBlockParent(core::ir::Block* dst, spvtools::opt::BasicBlock& src) { | 
 |         TINT_ASSERT(!InBlock(dst)); | 
 |  | 
 |         id_stack_.emplace_back(); | 
 |         current_blocks_.insert(dst); | 
 |  | 
 |         EmitBlock(dst, src); | 
 |  | 
 |         current_blocks_.erase(dst); | 
 |         id_stack_.pop_back(); | 
 |     } | 
 |  | 
 |     /// Emit the contents of SPIR-V block @p src into Tint IR block @p dst. | 
 |     /// @param dst the Tint IR block to append to | 
 |     /// @param src the SPIR-V block to emit | 
 |     void EmitBlock(core::ir::Block* dst, spvtools::opt::BasicBlock& src) { | 
 |         TINT_SCOPED_ASSIGNMENT(current_block_, dst); | 
 |  | 
 |         values_to_replace_.push_back({}); | 
 |  | 
 |         auto* loop_merge_inst = src.GetLoopMergeInst(); | 
 |         // This is a loop merge block, so we need to treat it as a Loop. | 
 |         if (loop_merge_inst) { | 
 |             // Emit the loop into the current block. | 
 |             EmitLoop(src); | 
 |  | 
 |             // The loop header is a walk stop block, which was created in the | 
 |             // emit loop method. Get the loop back so we can change the current | 
 |             // insertion block. | 
 |             auto* loop = StopWalkingAt(src.id())->As<core::ir::Loop>(); | 
 |             TINT_ASSERT(loop); | 
 |  | 
 |             id_stack_.emplace_back(); | 
 |             current_blocks_.insert(loop->Body()); | 
 |  | 
 |             // Now emit the remainder of the block into the loop body. | 
 |             current_block_ = loop->Body(); | 
 |         } | 
 |  | 
 |         spirv_id_to_block_.insert({src.id(), current_block_}); | 
 |  | 
 |         for (auto& inst : src) { | 
 |             switch (inst.opcode()) { | 
 |                 case spv::Op::OpNop: | 
 |                     break; | 
 |                 case spv::Op::OpUndef: | 
 |                     AddValue(inst.result_id(), b_.Zero(Type(inst.type_id()))); | 
 |                     break; | 
 |                 case spv::Op::OpBranch: | 
 |                     EmitBranch(inst); | 
 |                     break; | 
 |                 case spv::Op::OpBranchConditional: | 
 |                     EmitBranchConditional(src, inst); | 
 |                     break; | 
 |                 case spv::Op::OpSwitch: | 
 |                     EmitSwitch(src, inst); | 
 |                     break; | 
 |                 case spv::Op::OpLoopMerge: | 
 |                     EmitLoopMerge(src, inst); | 
 |                     break; | 
 |                 case spv::Op::OpSelectionMerge: | 
 |                     // Do nothing, the selection merge will be handled in the following | 
 |                     // OpBranchCondition or OpSwitch instruction | 
 |                     break; | 
 |                 case spv::Op::OpExtInst: | 
 |                     EmitExtInst(inst); | 
 |                     break; | 
 |                 case spv::Op::OpCopyObject: | 
 |                     EmitCopyObject(inst); | 
 |                     break; | 
 |                 case spv::Op::OpConvertFToS: | 
 |                     EmitSpirvExplicitBuiltinCall(inst, spirv::BuiltinFn::kConvertFToS); | 
 |                     break; | 
 |                 case spv::Op::OpConvertFToU: | 
 |                     Emit(b_.Convert(Type(inst.type_id()), Value(inst.GetSingleWordOperand(2))), | 
 |                          inst.result_id()); | 
 |                     break; | 
 |                 case spv::Op::OpConvertSToF: | 
 |                     EmitSpirvExplicitBuiltinCall(inst, spirv::BuiltinFn::kConvertSToF); | 
 |                     break; | 
 |                 case spv::Op::OpConvertUToF: | 
 |                     EmitSpirvExplicitBuiltinCall(inst, spirv::BuiltinFn::kConvertUToF); | 
 |                     break; | 
 |                 case spv::Op::OpFConvert: | 
 |                     Emit(b_.Convert(Type(inst.type_id()), Value(inst.GetSingleWordOperand(2))), | 
 |                          inst.result_id()); | 
 |                     break; | 
 |                 case spv::Op::OpBitwiseAnd: | 
 |                     EmitSpirvExplicitBuiltinCall(inst, spirv::BuiltinFn::kBitwiseAnd); | 
 |                     break; | 
 |                 case spv::Op::OpBitwiseOr: | 
 |                     EmitSpirvExplicitBuiltinCall(inst, spirv::BuiltinFn::kBitwiseOr); | 
 |                     break; | 
 |                 case spv::Op::OpBitwiseXor: | 
 |                     EmitSpirvExplicitBuiltinCall(inst, spirv::BuiltinFn::kBitwiseXor); | 
 |                     break; | 
 |                 case spv::Op::OpAccessChain: | 
 |                 case spv::Op::OpInBoundsAccessChain: | 
 |                     EmitAccess(inst); | 
 |                     break; | 
 |                 case spv::Op::OpCompositeInsert: | 
 |                     EmitCompositeInsert(inst); | 
 |                     break; | 
 |                 case spv::Op::OpCompositeConstruct: | 
 |                     EmitConstruct(inst); | 
 |                     break; | 
 |                 case spv::Op::OpCompositeExtract: | 
 |                     EmitCompositeExtract(inst); | 
 |                     break; | 
 |                 case spv::Op::OpVectorInsertDynamic: | 
 |                     EmitVectorInsertDynamic(inst); | 
 |                     break; | 
 |                 case spv::Op::OpFAdd: | 
 |                     EmitBinary(inst, core::BinaryOp::kAdd); | 
 |                     break; | 
 |                 case spv::Op::OpIAdd: | 
 |                     EmitSpirvExplicitBuiltinCall(inst, spirv::BuiltinFn::kAdd); | 
 |                     break; | 
 |                 case spv::Op::OpSDiv: | 
 |                     EmitSpirvExplicitBuiltinCall(inst, spirv::BuiltinFn::kSDiv); | 
 |                     break; | 
 |                 case spv::Op::OpFDiv: | 
 |                 case spv::Op::OpUDiv: | 
 |                     EmitBinary(inst, core::BinaryOp::kDivide); | 
 |                     break; | 
 |                 case spv::Op::OpIMul: | 
 |                     EmitSpirvExplicitBuiltinCall(inst, spirv::BuiltinFn::kMul); | 
 |                     break; | 
 |                 case spv::Op::OpFMul: | 
 |                 case spv::Op::OpVectorTimesScalar: | 
 |                 case spv::Op::OpMatrixTimesScalar: | 
 |                 case spv::Op::OpVectorTimesMatrix: | 
 |                 case spv::Op::OpMatrixTimesVector: | 
 |                 case spv::Op::OpMatrixTimesMatrix: | 
 |                     EmitBinary(inst, core::BinaryOp::kMultiply); | 
 |                     break; | 
 |                 case spv::Op::OpFRem: | 
 |                 case spv::Op::OpUMod: | 
 |                     EmitBinary(inst, core::BinaryOp::kModulo); | 
 |                     break; | 
 |                 case spv::Op::OpSMod: | 
 |                 case spv::Op::OpSRem: | 
 |                     EmitSpirvExplicitBuiltinCall(inst, spirv::BuiltinFn::kSMod); | 
 |                     break; | 
 |                 case spv::Op::OpFSub: | 
 |                     EmitBinary(inst, core::BinaryOp::kSubtract); | 
 |                     break; | 
 |                 case spv::Op::OpFOrdEqual: | 
 |                     EmitBinary(inst, core::BinaryOp::kEqual); | 
 |                     break; | 
 |                 case spv::Op::OpFOrdNotEqual: | 
 |                     EmitBinary(inst, core::BinaryOp::kNotEqual); | 
 |                     break; | 
 |                 case spv::Op::OpFOrdGreaterThan: | 
 |                     EmitBinary(inst, core::BinaryOp::kGreaterThan); | 
 |                     break; | 
 |                 case spv::Op::OpFOrdGreaterThanEqual: | 
 |                     EmitBinary(inst, core::BinaryOp::kGreaterThanEqual); | 
 |                     break; | 
 |                 case spv::Op::OpFOrdLessThan: | 
 |                     EmitBinary(inst, core::BinaryOp::kLessThan); | 
 |                     break; | 
 |                 case spv::Op::OpFOrdLessThanEqual: | 
 |                     EmitBinary(inst, core::BinaryOp::kLessThanEqual); | 
 |                     break; | 
 |                 case spv::Op::OpFUnordEqual: | 
 |                     EmitInvertedBinary(inst, core::BinaryOp::kNotEqual); | 
 |                     break; | 
 |                 case spv::Op::OpFUnordNotEqual: | 
 |                     EmitInvertedBinary(inst, core::BinaryOp::kEqual); | 
 |                     break; | 
 |                 case spv::Op::OpFUnordGreaterThan: | 
 |                     EmitInvertedBinary(inst, core::BinaryOp::kLessThanEqual); | 
 |                     break; | 
 |                 case spv::Op::OpFUnordGreaterThanEqual: | 
 |                     EmitInvertedBinary(inst, core::BinaryOp::kLessThan); | 
 |                     break; | 
 |                 case spv::Op::OpFUnordLessThan: | 
 |                     EmitInvertedBinary(inst, core::BinaryOp::kGreaterThanEqual); | 
 |                     break; | 
 |                 case spv::Op::OpFUnordLessThanEqual: | 
 |                     EmitInvertedBinary(inst, core::BinaryOp::kGreaterThan); | 
 |                     break; | 
 |                 case spv::Op::OpIEqual: | 
 |                     EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kEqual); | 
 |                     break; | 
 |                 case spv::Op::OpINotEqual: | 
 |                     EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kNotEqual); | 
 |                     break; | 
 |                 case spv::Op::OpSGreaterThan: | 
 |                     EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kSGreaterThan); | 
 |                     break; | 
 |                 case spv::Op::OpSGreaterThanEqual: | 
 |                     EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kSGreaterThanEqual); | 
 |                     break; | 
 |                 case spv::Op::OpSLessThan: | 
 |                     EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kSLessThan); | 
 |                     break; | 
 |                 case spv::Op::OpSLessThanEqual: | 
 |                     EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kSLessThanEqual); | 
 |                     break; | 
 |                 case spv::Op::OpUGreaterThan: | 
 |                     EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kUGreaterThan); | 
 |                     break; | 
 |                 case spv::Op::OpUGreaterThanEqual: | 
 |                     EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kUGreaterThanEqual); | 
 |                     break; | 
 |                 case spv::Op::OpULessThan: | 
 |                     EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kULessThan); | 
 |                     break; | 
 |                 case spv::Op::OpULessThanEqual: | 
 |                     EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kULessThanEqual); | 
 |                     break; | 
 |                 case spv::Op::OpISub: | 
 |                     EmitSpirvExplicitBuiltinCall(inst, spirv::BuiltinFn::kSub); | 
 |                     break; | 
 |                 case spv::Op::OpFunctionCall: | 
 |                     EmitFunctionCall(inst); | 
 |                     break; | 
 |                 case spv::Op::OpLoad: | 
 |                     Emit(b_.Load(Value(inst.GetSingleWordOperand(2))), inst.result_id()); | 
 |                     break; | 
 |                 case spv::Op::OpReturn: | 
 |                     EmitWithoutResult(b_.Return(current_function_)); | 
 |                     break; | 
 |                 case spv::Op::OpReturnValue: | 
 |                     EmitWithoutResult( | 
 |                         b_.Return(current_function_, Value(inst.GetSingleWordOperand(0)))); | 
 |                     break; | 
 |                 case spv::Op::OpStore: | 
 |                     EmitWithoutResult(b_.Store(Value(inst.GetSingleWordOperand(0)), | 
 |                                                Value(inst.GetSingleWordOperand(1)))); | 
 |                     break; | 
 |                 case spv::Op::OpCopyMemory: | 
 |                     EmitCopyMemory(inst); | 
 |                     break; | 
 |                 case spv::Op::OpVariable: | 
 |                     EmitVar(inst); | 
 |                     break; | 
 |                 case spv::Op::OpUnreachable: | 
 |                     EmitWithoutResult(b_.Unreachable()); | 
 |                     break; | 
 |                 case spv::Op::OpKill: | 
 |                     EmitKill(inst); | 
 |                     break; | 
 |                 case spv::Op::OpDot: | 
 |                     EmitBuiltinCall(inst, core::BuiltinFn::kDot); | 
 |                     break; | 
 |                 case spv::Op::OpBitCount: | 
 |                     EmitBitCount(inst); | 
 |                     break; | 
 |                 case spv::Op::OpBitFieldInsert: | 
 |                     EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kBitFieldInsert); | 
 |                     break; | 
 |                 case spv::Op::OpBitFieldSExtract: | 
 |                     EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kBitFieldSExtract); | 
 |                     break; | 
 |                 case spv::Op::OpBitFieldUExtract: | 
 |                     EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kBitFieldUExtract); | 
 |                     break; | 
 |                 case spv::Op::OpBitReverse: | 
 |                     EmitBuiltinCall(inst, core::BuiltinFn::kReverseBits); | 
 |                     break; | 
 |                 case spv::Op::OpAll: | 
 |                     EmitBuiltinCall(inst, core::BuiltinFn::kAll); | 
 |                     break; | 
 |                 case spv::Op::OpAny: | 
 |                     EmitBuiltinCall(inst, core::BuiltinFn::kAny); | 
 |                     break; | 
 |                 case spv::Op::OpDPdx: | 
 |                     EmitBuiltinCall(inst, core::BuiltinFn::kDpdx); | 
 |                     break; | 
 |                 case spv::Op::OpDPdy: | 
 |                     EmitBuiltinCall(inst, core::BuiltinFn::kDpdy); | 
 |                     break; | 
 |                 case spv::Op::OpFwidth: | 
 |                     EmitBuiltinCall(inst, core::BuiltinFn::kFwidth); | 
 |                     break; | 
 |                 case spv::Op::OpDPdxFine: | 
 |                     EmitBuiltinCall(inst, core::BuiltinFn::kDpdxFine); | 
 |                     break; | 
 |                 case spv::Op::OpDPdyFine: | 
 |                     EmitBuiltinCall(inst, core::BuiltinFn::kDpdyFine); | 
 |                     break; | 
 |                 case spv::Op::OpFwidthFine: | 
 |                     EmitBuiltinCall(inst, core::BuiltinFn::kFwidthFine); | 
 |                     break; | 
 |                 case spv::Op::OpDPdxCoarse: | 
 |                     EmitBuiltinCall(inst, core::BuiltinFn::kDpdxCoarse); | 
 |                     break; | 
 |                 case spv::Op::OpDPdyCoarse: | 
 |                     EmitBuiltinCall(inst, core::BuiltinFn::kDpdyCoarse); | 
 |                     break; | 
 |                 case spv::Op::OpFwidthCoarse: | 
 |                     EmitBuiltinCall(inst, core::BuiltinFn::kFwidthCoarse); | 
 |                     break; | 
 |                 case spv::Op::OpLogicalAnd: | 
 |                     EmitBinary(inst, core::BinaryOp::kAnd); | 
 |                     break; | 
 |                 case spv::Op::OpLogicalOr: | 
 |                     EmitBinary(inst, core::BinaryOp::kOr); | 
 |                     break; | 
 |                 case spv::Op::OpLogicalEqual: | 
 |                     EmitBinary(inst, core::BinaryOp::kEqual); | 
 |                     break; | 
 |                 case spv::Op::OpLogicalNotEqual: | 
 |                     EmitBinary(inst, core::BinaryOp::kNotEqual); | 
 |                     break; | 
 |                 case spv::Op::OpLogicalNot: | 
 |                     EmitUnary(inst, core::UnaryOp::kNot); | 
 |                     break; | 
 |                 case spv::Op::OpFNegate: | 
 |                     EmitUnary(inst, core::UnaryOp::kNegation); | 
 |                     break; | 
 |                 case spv::Op::OpNot: | 
 |                     EmitSpirvExplicitBuiltinCall(inst, spirv::BuiltinFn::kNot); | 
 |                     break; | 
 |                 case spv::Op::OpShiftLeftLogical: | 
 |                     EmitSpirvExplicitBuiltinCall(inst, spirv::BuiltinFn::kShiftLeftLogical); | 
 |                     break; | 
 |                 case spv::Op::OpShiftRightLogical: | 
 |                     EmitSpirvExplicitBuiltinCall(inst, spirv::BuiltinFn::kShiftRightLogical); | 
 |                     break; | 
 |                 case spv::Op::OpShiftRightArithmetic: | 
 |                     EmitSpirvExplicitBuiltinCall(inst, spirv::BuiltinFn::kShiftRightArithmetic); | 
 |                     break; | 
 |                 case spv::Op::OpBitcast: | 
 |                     EmitBitcast(inst); | 
 |                     break; | 
 |                 case spv::Op::OpQuantizeToF16: | 
 |                     EmitBuiltinCall(inst, core::BuiltinFn::kQuantizeToF16); | 
 |                     break; | 
 |                 case spv::Op::OpTranspose: | 
 |                     EmitBuiltinCall(inst, core::BuiltinFn::kTranspose); | 
 |                     break; | 
 |                 case spv::Op::OpSNegate: | 
 |                     EmitSpirvExplicitBuiltinCall(inst, spirv::BuiltinFn::kSNegate); | 
 |                     break; | 
 |                 case spv::Op::OpFMod: | 
 |                     EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kFMod); | 
 |                     break; | 
 |                 case spv::Op::OpSelect: | 
 |                     EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kSelect); | 
 |                     break; | 
 |                 case spv::Op::OpVectorExtractDynamic: | 
 |                     EmitAccess(inst); | 
 |                     break; | 
 |                 case spv::Op::OpOuterProduct: | 
 |                     EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kOuterProduct); | 
 |                     break; | 
 |                 case spv::Op::OpVectorShuffle: | 
 |                     EmitVectorShuffle(inst); | 
 |                     break; | 
 |                 case spv::Op::OpAtomicStore: | 
 |                     EmitAtomicStore(inst); | 
 |                     break; | 
 |                 case spv::Op::OpAtomicLoad: | 
 |                     CheckAtomicNotFloat(inst); | 
 |                     EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kAtomicLoad); | 
 |                     break; | 
 |                 case spv::Op::OpAtomicIAdd: | 
 |                     EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kAtomicIAdd); | 
 |                     break; | 
 |                 case spv::Op::OpAtomicISub: | 
 |                     EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kAtomicISub); | 
 |                     break; | 
 |                 case spv::Op::OpAtomicAnd: | 
 |                     EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kAtomicAnd); | 
 |                     break; | 
 |                 case spv::Op::OpAtomicOr: | 
 |                     EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kAtomicOr); | 
 |                     break; | 
 |                 case spv::Op::OpAtomicXor: | 
 |                     EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kAtomicXor); | 
 |                     break; | 
 |                 case spv::Op::OpAtomicSMin: | 
 |                     EmitAtomicSigned(inst, spirv::BuiltinFn::kAtomicSMin); | 
 |                     break; | 
 |                 case spv::Op::OpAtomicUMin: | 
 |                     EmitAtomicUnsigned(inst, spirv::BuiltinFn::kAtomicUMin); | 
 |                     break; | 
 |                 case spv::Op::OpAtomicSMax: | 
 |                     EmitAtomicSigned(inst, spirv::BuiltinFn::kAtomicSMax); | 
 |                     break; | 
 |                 case spv::Op::OpAtomicUMax: | 
 |                     EmitAtomicUnsigned(inst, spirv::BuiltinFn::kAtomicUMax); | 
 |                     break; | 
 |                 case spv::Op::OpAtomicExchange: | 
 |                     CheckAtomicNotFloat(inst); | 
 |                     EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kAtomicExchange); | 
 |                     break; | 
 |                 case spv::Op::OpAtomicCompareExchange: | 
 |                     EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kAtomicCompareExchange); | 
 |                     break; | 
 |                 case spv::Op::OpAtomicIIncrement: | 
 |                     EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kAtomicIIncrement); | 
 |                     break; | 
 |                 case spv::Op::OpAtomicIDecrement: | 
 |                     EmitSpirvBuiltinCall(inst, spirv::BuiltinFn::kAtomicIDecrement); | 
 |                     break; | 
 |                 case spv::Op::OpControlBarrier: | 
 |                     EmitControlBarrier(inst); | 
 |                     break; | 
 |                 case spv::Op::OpArrayLength: | 
 |                     EmitArrayLength(inst); | 
 |                     break; | 
 |                 case spv::Op::OpSampledImage: | 
 |                     EmitSampledImage(inst); | 
 |                     break; | 
 |                 case spv::Op::OpImage: | 
 |                     EmitImage(inst); | 
 |                     break; | 
 |                 case spv::Op::OpImageFetch: | 
 |                     EmitImageFetchOrRead(inst, spirv::BuiltinFn::kImageFetch); | 
 |                     break; | 
 |                 case spv::Op::OpImageRead: | 
 |                     EmitImageFetchOrRead(inst, spirv::BuiltinFn::kImageRead); | 
 |                     break; | 
 |                 case spv::Op::OpImageGather: | 
 |                     EmitImageGather(inst); | 
 |                     break; | 
 |                 case spv::Op::OpImageQueryLevels: | 
 |                     EmitImageQuery(inst, spirv::BuiltinFn::kImageQueryLevels); | 
 |                     break; | 
 |                 case spv::Op::OpImageQuerySamples: | 
 |                     EmitImageQuery(inst, spirv::BuiltinFn::kImageQuerySamples); | 
 |                     break; | 
 |                 case spv::Op::OpImageQuerySize: | 
 |                     EmitImageQuery(inst, spirv::BuiltinFn::kImageQuerySize); | 
 |                     break; | 
 |                 case spv::Op::OpImageQuerySizeLod: | 
 |                     EmitImageQuerySizeLod(inst); | 
 |                     break; | 
 |                 case spv::Op::OpImageSampleExplicitLod: | 
 |                     EmitImageSample(inst, spirv::BuiltinFn::kImageSampleExplicitLod); | 
 |                     break; | 
 |                 case spv::Op::OpImageSampleImplicitLod: | 
 |                     EmitImageSample(inst, spirv::BuiltinFn::kImageSampleImplicitLod); | 
 |                     break; | 
 |                 case spv::Op::OpImageSampleProjImplicitLod: | 
 |                     EmitImageSample(inst, spirv::BuiltinFn::kImageSampleProjImplicitLod); | 
 |                     break; | 
 |                 case spv::Op::OpImageSampleProjExplicitLod: | 
 |                     EmitImageSample(inst, spirv::BuiltinFn::kImageSampleProjExplicitLod); | 
 |                     break; | 
 |                 case spv::Op::OpImageWrite: | 
 |                     EmitImageWrite(inst); | 
 |                     break; | 
 |                 case spv::Op::OpImageSampleDrefImplicitLod: | 
 |                     EmitImageSampleDepth(inst, spirv::BuiltinFn::kImageSampleDrefImplicitLod); | 
 |                     break; | 
 |                 case spv::Op::OpImageSampleDrefExplicitLod: | 
 |                     EmitImageSampleDepth(inst, spirv::BuiltinFn::kImageSampleDrefExplicitLod); | 
 |                     break; | 
 |                 case spv::Op::OpImageSampleProjDrefImplicitLod: | 
 |                     EmitImageSampleDepth(inst, spirv::BuiltinFn::kImageSampleProjDrefImplicitLod); | 
 |                     break; | 
 |                 case spv::Op::OpImageSampleProjDrefExplicitLod: | 
 |                     EmitImageSampleDepth(inst, spirv::BuiltinFn::kImageSampleProjDrefExplicitLod); | 
 |                     break; | 
 |                 case spv::Op::OpImageDrefGather: | 
 |                     EmitImageGatherDref(inst); | 
 |                     break; | 
 |                 case spv::Op::OpPhi: | 
 |                     EmitPhi(inst); | 
 |                     break; | 
 |                 default: | 
 |                     TINT_UNIMPLEMENTED() | 
 |                         << "unhandled SPIR-V instruction: " << static_cast<uint32_t>(inst.opcode()); | 
 |             } | 
 |         } | 
 |  | 
 |         // The loop merge needs to be emitted if this was a loop block. It has | 
 |         // to be emitted back into the original destination. | 
 |         if (loop_merge_inst) { | 
 |             auto* loop = StopWalkingAt(src.id())->As<core::ir::Loop>(); | 
 |             TINT_ASSERT(loop); | 
 |  | 
 |             // Add the body terminator if necessary | 
 |             if (!loop->Body()->Terminator()) { | 
 |                 loop->Body()->Append(b_.Unreachable()); | 
 |             } | 
 |  | 
 |             // Push id stack entry for the continuing block. We don't use EmitBlockParent to do this | 
 |             // because we need the scope to exist until after we process any `continue_blk_phis_`. | 
 |             id_stack_.emplace_back(); | 
 |  | 
 |             auto continue_id = loop_merge_inst->GetSingleWordInOperand(1); | 
 |  | 
 |             // We only need to emit the continuing block if: | 
 |             //  a) It is not the loop header | 
 |             //  b) It has inbound branches. This works around a case where you can have a continuing | 
 |             //     where uses values which are very difficult to propagate, but the continuing is | 
 |             //     never reached anyway, so the propagation is useless. | 
 |             if (continue_id != src.id() && | 
 |                 !loop->Continuing()->InboundSiblingBranches().IsEmpty()) { | 
 |                 const auto& bb_continue = current_spirv_function_->FindBlock(continue_id); | 
 |  | 
 |                 current_blocks_.insert(loop->Continuing()); | 
 |                 // Emit the continuing block. | 
 |                 EmitBlock(loop->Continuing(), *bb_continue); | 
 |  | 
 |                 current_blocks_.erase(loop->Continuing()); | 
 |             } | 
 |  | 
 |             if (!loop->Continuing()->Terminator()) { | 
 |                 loop->Continuing()->Append(b_.NextIteration(loop)); | 
 |             } | 
 |  | 
 |             // If this continue block needs to pass any `phi` instructions back to | 
 |             // the main loop body. | 
 |             // | 
 |             // We have to do this here because we need to have emitted the loop | 
 |             // body before we can get the values used in the continue block. | 
 |             auto phis = continue_blk_phis_.find(continue_id); | 
 |             if (phis != continue_blk_phis_.end()) { | 
 |                 for (auto value_id : phis->second) { | 
 |                     auto* value = Value(value_id); | 
 |  | 
 |                     tint::Switch( | 
 |                         loop->Continuing()->Terminator(),  // | 
 |                         [&](core::ir::NextIteration* ni) { ni->PushOperand(value); }, | 
 |                         [&](core::ir::BreakIf* bi) { | 
 |                             // TODO(dsinclair): Need to change the break-if insertion of there | 
 |                             // happens to be exit values, but those are rare, so leave this for when | 
 |                             // we have test case. | 
 |                             TINT_ASSERT(bi->ExitValues().IsEmpty()); | 
 |  | 
 |                             auto len = bi->NextIterValues().Length(); | 
 |                             bi->PushOperand(value); | 
 |                             bi->SetNumNextIterValues(len + 1); | 
 |                         }, | 
 |                         TINT_ICE_ON_NO_MATCH); | 
 |                 } | 
 |             } | 
 |  | 
 |             id_stack_.pop_back(); | 
 |         } | 
 |  | 
 |         // For any `OpPhi` values we saw, insert their `Value` now. We do this | 
 |         // at the end of the loop because a phi can refer to instructions | 
 |         // defined after it in the block. | 
 |         auto replace = values_to_replace_.back(); | 
 |         for (auto& val : replace) { | 
 |             auto* value = ValueNoPropagate(val.value_id); | 
 |             val.terminator->SetOperand(val.idx, value); | 
 |         } | 
 |         values_to_replace_.pop_back(); | 
 |  | 
 |         if (loop_merge_inst) { | 
 |             auto* loop = StopWalkingAt(src.id())->As<core::ir::Loop>(); | 
 |             TINT_ASSERT(loop); | 
 |  | 
 |             current_blocks_.erase(loop->Body()); | 
 |             id_stack_.pop_back(); | 
 |  | 
 |             // If we added phi's to the continuing block, we may have exits from the body which | 
 |             // aren't valid. | 
 |             auto continuing_param_count = loop->Continuing()->Params().Length(); | 
 |             if (continuing_param_count > 0) { | 
 |                 for (auto incoming : loop->Continuing()->InboundSiblingBranches()) { | 
 |                     TINT_ASSERT(incoming->Is<core::ir::Continue>()); | 
 |  | 
 |                     // Check if the block this instruction exists in has default phi result that we | 
 |                     // can append. | 
 |                     auto inst_to_blk_iter = inst_to_spirv_block_.find(incoming); | 
 |                     if (inst_to_blk_iter != inst_to_spirv_block_.end()) { | 
 |                         uint32_t spirv_blk = inst_to_blk_iter->second; | 
 |                         auto phi_values_from_loop_header = block_phi_values_[spirv_blk]; | 
 |                         // If there were phi values, push them to this instruction | 
 |                         for (auto value_id : phi_values_from_loop_header) { | 
 |                             auto* value = Value(value_id); | 
 |                             incoming->PushOperand(value); | 
 |                         } | 
 |                     } | 
 |                 } | 
 |             } | 
 |  | 
 |             // Emit the merge block | 
 |             auto merge_id = loop_merge_inst->GetSingleWordInOperand(0); | 
 |             const auto& merge_bb = current_spirv_function_->FindBlock(merge_id); | 
 |             EmitBlock(dst, *merge_bb); | 
 |         } | 
 |     } | 
 |  | 
 |     struct IfBranchValue { | 
 |         core::ir::Value* value; | 
 |         core::ir::If* if_; | 
 |     }; | 
 |  | 
 |     void EmitPhi(spvtools::opt::Instruction& inst) { | 
 |         auto num_ops = inst.NumInOperands(); | 
 |  | 
 |         // If there are only 2 arguments, that means we came directly from a block, so just emit the | 
 |         // value directly. | 
 |         if (num_ops == 2) { | 
 |             AddValue(inst.result_id(), Value(inst.GetSingleWordInOperand(0))); | 
 |             return; | 
 |         } | 
 |  | 
 |         std::unordered_map<core::ir::ControlInstruction*, const core::type::Type*> | 
 |             ctrl_inst_result_types; | 
 |         std::unordered_map<core::ir::MultiInBlock*, const core::type::Type*> blk_to_param_types; | 
 |  | 
 |         std::optional<IfBranchValue> if_to_update_branch; | 
 |  | 
 |         auto add_ctrl_inst = [&](core::ir::ControlInstruction* ctrl, const core::type::Type* type) { | 
 |             auto iter = ctrl_inst_result_types.find(ctrl); | 
 |             if (iter != ctrl_inst_result_types.end()) { | 
 |                 TINT_ASSERT(iter->second == type); | 
 |                 return; | 
 |             } | 
 |             ctrl_inst_result_types.insert({ctrl, type}); | 
 |         }; | 
 |  | 
 |         auto* type = Type(inst.type_id()); | 
 |         auto add_blk_inst = [&](core::ir::MultiInBlock* blk) { | 
 |             auto iter = blk_to_param_types.find(blk); | 
 |             if (iter != blk_to_param_types.end()) { | 
 |                 TINT_ASSERT(iter->second == type); | 
 |                 return; | 
 |             } | 
 |             blk_to_param_types.insert({blk, type}); | 
 |         }; | 
 |  | 
 |         auto* phi_spirv_block = spirv_context_->get_instr_block(&inst); | 
 |         auto* phi_loop_merge_inst = phi_spirv_block->GetLoopMergeInst(); | 
 |  | 
 |         for (uint32_t i = 0; i < num_ops; i += 2) { | 
 |             auto value_id = inst.GetSingleWordInOperand(i); | 
 |             auto blk_id = inst.GetSingleWordInOperand(i + 1); | 
 |  | 
 |             // Store this value away as a default phi value for this loop header. | 
 |             block_phi_values_[blk_id].push_back(value_id); | 
 |  | 
 |             auto value_blk_iter = spirv_id_to_block_.find(blk_id); | 
 |  | 
 |             // The referenced block hasn't been emitted yet (continue blocks have this | 
 |             // behaviour). So, store the fact that it needs to return a given value away for | 
 |             // when we do emit the block. | 
 |             if (value_blk_iter == spirv_id_to_block_.end()) { | 
 |                 auto continue_id = phi_loop_merge_inst->GetSingleWordInOperand(1); | 
 |  | 
 |                 // Note, we push it to the `continue_id` as the block and not | 
 |                 // `blk_id` so that we can emit them into the continuing block as | 
 |                 // a group. | 
 |                 continue_blk_phis_[continue_id].push_back(value_id); | 
 |  | 
 |                 // Add the phi to the current block set of input parameters | 
 |                 auto* mb = current_block_->As<core::ir::MultiInBlock>(); | 
 |                 TINT_ASSERT(mb); | 
 |                 add_blk_inst(mb); | 
 |                 continue; | 
 |             } | 
 |  | 
 |             core::ir::Terminator* term = nullptr; | 
 |  | 
 |             // The `OpPhi` is part of a loop header block, treat it special as we need to insert | 
 |             // things into the phi's loop initializer/body/continuing block as needed. | 
 |             if (phi_loop_merge_inst) { | 
 |                 auto* loop = StopWalkingAt(phi_spirv_block->id())->As<core::ir::Loop>(); | 
 |                 TINT_ASSERT(loop); | 
 |  | 
 |                 // A phi from an explicit continue block is handled above as we haven't emitted the | 
 |                 // continue block so we wouldn't find it in the `spirv_id_to_block` list. | 
 |  | 
 |                 // If this loop header is also the continue block | 
 |                 if (blk_id == phi_spirv_block->id()) { | 
 |                     if (loop->Continuing()->IsEmpty()) { | 
 |                         b_.Append(loop->Continuing(), [&] { term = b_.NextIteration(loop); }); | 
 |                         add_blk_inst(loop->Body()); | 
 |                     } else { | 
 |                         // With multiple phis we my have already created the continuing | 
 |                         // block, so just get the terminator. | 
 |                         term = loop->Continuing()->Terminator(); | 
 |                         TINT_ASSERT(term->Is<core::ir::NextIteration>()); | 
 |                     } | 
 |                 } else { | 
 |                     // We know this isn't the continue as it hasn't emitted yet, so this has to be | 
 |                     // coming from the calling block. So, we need to add this item into the | 
 |                     // initializer `NextIteration` and as a parameter to the body. | 
 |                     if (loop->Initializer()->IsEmpty()) { | 
 |                         b_.Append(loop->Initializer(), [&] { term = b_.NextIteration(loop); }); | 
 |                         add_blk_inst(loop->Body()); | 
 |                     } else { | 
 |                         term = loop->Initializer()->Terminator(); | 
 |                         TINT_ASSERT(term->Is<core::ir::NextIteration>()); | 
 |                     } | 
 |                 } | 
 |  | 
 |             } else { | 
 |                 auto* value_ir_blk = value_blk_iter->second; | 
 |  | 
 |                 // We know the phi isn't part of a loop. That means, all of the blocks making up the | 
 |                 // phi are known. The one trick is that an `if` may only have a single block (the | 
 |                 // true or false). In that case, we have to push the value into the other block | 
 |                 // as it has to return something. | 
 |                 // | 
 |                 // For a `Switch` we will have all the cases already so we can just get the | 
 |                 // terminator for the block. | 
 |  | 
 |                 if (!value_ir_blk->Terminator()) { | 
 |                     auto* if_ = value_ir_blk->Back()->As<core::ir::If>(); | 
 |                     TINT_ASSERT(if_); | 
 |                     // No block terminator means the block that the `phi` is referencing | 
 |                     // isn't finished (in IR-land). This can only happen with an `if` | 
 |                     // instruction where you've branched directly to the `phi` as either the | 
 |                     // `then` or `else` clause. | 
 |  | 
 |                     TINT_ASSERT(!if_to_update_branch.has_value()); | 
 |  | 
 |                     auto* value = ValueNoPropagate(value_id); | 
 |                     if_to_update_branch = IfBranchValue{ | 
 |                         .value = value, | 
 |                         .if_ = if_, | 
 |                     }; | 
 |  | 
 |                     continue; | 
 |                 } | 
 |                 term = value_ir_blk->Terminator(); | 
 |             } | 
 |  | 
 |             // If we can't get to this part of the control flow, ignore the phi | 
 |             if (term->Is<core::ir::Unreachable>()) { | 
 |                 continue; | 
 |             } | 
 |  | 
 |             // Push a placeholder for the operand value at this point. We'll | 
 |             // store away the terminator/index pair along with the required | 
 |             // value and then fill it in at the end of the block emission. | 
 |             auto operand_idx = term->PushOperand(nullptr); | 
 |             values_to_replace_.back().push_back(ReplacementValue{ | 
 |                 .terminator = term, | 
 |                 .idx = operand_idx, | 
 |                 .value_id = value_id, | 
 |             }); | 
 |  | 
 |             // For each incoming block to the phi, store either the control | 
 |             // instruction to be updated, or the block to be updated and the | 
 |             // type of result to return. | 
 |             tint::Switch( | 
 |                 term,  // | 
 |                 [&](core::ir::Exit* exit) { add_ctrl_inst(exit->ControlInstruction(), type); }, | 
 |                 [&](core::ir::BreakIf* bi) { add_ctrl_inst(bi->Loop(), type); }, | 
 |                 [&](core::ir::Continue* cont) { add_blk_inst(cont->Loop()->Continuing()); }, | 
 |                 [&](core::ir::NextIteration* ni) { add_blk_inst(ni->Loop()->Body()); }, | 
 |                 TINT_ICE_ON_NO_MATCH); | 
 |         } | 
 |  | 
 |         // We need to update one of the two `if` branches with the return value. | 
 |         // Find the one where the terminator has less operands and update that | 
 |         // one. | 
 |         if (if_to_update_branch.has_value()) { | 
 |             auto* value = if_to_update_branch->value; | 
 |             auto* if_ = if_to_update_branch->if_; | 
 |  | 
 |             core::ir::Terminator* term = nullptr; | 
 |  | 
 |             if (if_->True()->Terminator()->Operands().Length() < | 
 |                 if_->False()->Terminator()->Operands().Length()) { | 
 |                 term = if_->True()->Terminator(); | 
 |             } else { | 
 |                 term = if_->False()->Terminator(); | 
 |             } | 
 |  | 
 |             term->PushOperand(value); | 
 |             add_ctrl_inst(if_, value->Type()); | 
 |         } | 
 |  | 
 |         // Update control instruction results to contain the new type. | 
 |         for (auto info : ctrl_inst_result_types) { | 
 |             auto* ctrl = info.first; | 
 |             auto* res_type = info.second; | 
 |             auto* res = b_.InstructionResult(res_type); | 
 |             ctrl->AddResult(res); | 
 |             values_.Replace(inst.result_id(), res); | 
 |         } | 
 |  | 
 |         // Update block params to contain the new type. | 
 |         for (auto info : blk_to_param_types) { | 
 |             auto* blk = info.first; | 
 |             auto* param_type = info.second; | 
 |  | 
 |             auto* p = b_.BlockParam(param_type); | 
 |             blk->AddParam(p); | 
 |  | 
 |             TINT_ASSERT(blk == current_block_); | 
 |             AddValue(inst.result_id(), p); | 
 |         } | 
 |     } | 
 |  | 
 |     void EmitImage(const spvtools::opt::Instruction& inst) { | 
 |         auto* si = Value(inst.GetSingleWordInOperand(0)); | 
 |         Emit(b_.CallExplicit<spirv::ir::BuiltinCall>( | 
 |                  Type(inst.type_id()), spirv::BuiltinFn::kImage, | 
 |                  Vector{si->Type()->As<spirv::type::SampledImage>()->Image()}, Args(inst, 2)), | 
 |              inst.result_id()); | 
 |     } | 
 |  | 
 |     void EmitSampledImage(const spvtools::opt::Instruction& inst) { | 
 |         auto* tex = Value(inst.GetSingleWordInOperand(0)); | 
 |         Emit(b_.CallExplicit<spirv::ir::BuiltinCall>(Type(inst.type_id()), | 
 |                                                      spirv::BuiltinFn::kSampledImage, | 
 |                                                      Vector{tex->Type()}, Args(inst, 2)), | 
 |              inst.result_id()); | 
 |     } | 
 |  | 
 |     void EmitImageFetchOrRead(const spvtools::opt::Instruction& inst, spirv::BuiltinFn fn) { | 
 |         auto sampled_image = Value(inst.GetSingleWordInOperand(0)); | 
 |         auto* coord = Value(inst.GetSingleWordInOperand(1)); | 
 |  | 
 |         Vector<core::ir::Value*, 4> args = {sampled_image, coord}; | 
 |  | 
 |         if (inst.NumInOperands() > 2) { | 
 |             uint32_t literal_mask = inst.GetSingleWordInOperand(2); | 
 |             args.Push(b_.Constant(u32(literal_mask))); | 
 |  | 
 |             if (literal_mask != 0) { | 
 |                 args.Push(Value(inst.GetSingleWordInOperand(3))); | 
 |             } | 
 |         } else { | 
 |             args.Push(b_.Zero(ty_.u32())); | 
 |         } | 
 |  | 
 |         Emit(b_.Call<spirv::ir::BuiltinCall>(Type(inst.type_id()), fn, args), inst.result_id()); | 
 |     } | 
 |  | 
 |     void EmitImageGatherDref(const spvtools::opt::Instruction& inst) { | 
 |         auto sampled_image = Value(inst.GetSingleWordInOperand(0)); | 
 |         auto* coord = Value(inst.GetSingleWordInOperand(1)); | 
 |         auto* dref = Value(inst.GetSingleWordInOperand(2)); | 
 |  | 
 |         Vector<core::ir::Value*, 4> args = {sampled_image, coord, dref}; | 
 |  | 
 |         if (inst.NumInOperands() > 3) { | 
 |             uint32_t literal_mask = inst.GetSingleWordInOperand(3); | 
 |             args.Push(b_.Constant(u32(literal_mask))); | 
 |  | 
 |             if (literal_mask != 0) { | 
 |                 TINT_ASSERT(static_cast<spv::ImageOperandsMask>(literal_mask) == | 
 |                             spv::ImageOperandsMask::ConstOffset); | 
 |                 TINT_ASSERT(inst.NumInOperands() > 4); | 
 |                 args.Push(Value(inst.GetSingleWordInOperand(4))); | 
 |             } | 
 |         } else { | 
 |             args.Push(b_.Zero(ty_.u32())); | 
 |         } | 
 |  | 
 |         Emit(b_.Call<spirv::ir::BuiltinCall>(Type(inst.type_id()), | 
 |                                              spirv::BuiltinFn::kImageDrefGather, args), | 
 |              inst.result_id()); | 
 |     } | 
 |  | 
 |     void EmitImageGather(const spvtools::opt::Instruction& inst) { | 
 |         auto sampled_image = Value(inst.GetSingleWordInOperand(0)); | 
 |         auto* coord = Value(inst.GetSingleWordInOperand(1)); | 
 |         auto* comp = Value(inst.GetSingleWordInOperand(2)); | 
 |  | 
 |         Vector<core::ir::Value*, 4> args = {sampled_image, coord, comp}; | 
 |  | 
 |         if (inst.NumInOperands() > 3) { | 
 |             uint32_t literal_mask = inst.GetSingleWordInOperand(3); | 
 |             args.Push(b_.Constant(u32(literal_mask))); | 
 |  | 
 |             if (literal_mask != 0) { | 
 |                 TINT_ASSERT(static_cast<spv::ImageOperandsMask>(literal_mask) == | 
 |                             spv::ImageOperandsMask::ConstOffset); | 
 |                 TINT_ASSERT(inst.NumInOperands() > 4); | 
 |                 args.Push(Value(inst.GetSingleWordInOperand(4))); | 
 |             } | 
 |         } else { | 
 |             args.Push(b_.Zero(ty_.u32())); | 
 |         } | 
 |  | 
 |         Emit(b_.Call<spirv::ir::BuiltinCall>(Type(inst.type_id()), spirv::BuiltinFn::kImageGather, | 
 |                                              args), | 
 |              inst.result_id()); | 
 |     } | 
 |  | 
 |     void EmitImageSample(const spvtools::opt::Instruction& inst, spirv::BuiltinFn fn) { | 
 |         auto sampled_image = Value(inst.GetSingleWordInOperand(0)); | 
 |         auto* coord = Value(inst.GetSingleWordInOperand(1)); | 
 |  | 
 |         Vector<core::ir::Value*, 4> args = {sampled_image, coord}; | 
 |  | 
 |         if (inst.NumInOperands() > 2) { | 
 |             uint32_t literal_mask = inst.GetSingleWordInOperand(2); | 
 |             args.Push(b_.Constant(u32(literal_mask))); | 
 |  | 
 |             if (literal_mask != 0) { | 
 |                 TINT_ASSERT(inst.NumInOperands() > 3); | 
 |             } | 
 |  | 
 |             for (uint32_t i = 3; i < inst.NumInOperands(); ++i) { | 
 |                 args.Push(Value(inst.GetSingleWordInOperand(i))); | 
 |             } | 
 |         } else { | 
 |             args.Push(b_.Zero(ty_.u32())); | 
 |         } | 
 |  | 
 |         Emit(b_.Call<spirv::ir::BuiltinCall>(Type(inst.type_id()), fn, args), inst.result_id()); | 
 |     } | 
 |  | 
 |     void EmitImageSampleDepth(const spvtools::opt::Instruction& inst, spirv::BuiltinFn fn) { | 
 |         auto sampled_image = Value(inst.GetSingleWordInOperand(0)); | 
 |         auto* coord = Value(inst.GetSingleWordInOperand(1)); | 
 |         auto* dref = Value(inst.GetSingleWordInOperand(2)); | 
 |  | 
 |         Vector<core::ir::Value*, 4> args = {sampled_image, coord, dref}; | 
 |  | 
 |         if (inst.NumInOperands() > 3) { | 
 |             uint32_t literal_mask = inst.GetSingleWordInOperand(3); | 
 |             args.Push(b_.Constant(u32(literal_mask))); | 
 |  | 
 |             if (literal_mask != 0) { | 
 |                 TINT_ASSERT(inst.NumInOperands() > 4); | 
 |             } | 
 |  | 
 |             for (uint32_t i = 4; i < inst.NumInOperands(); ++i) { | 
 |                 args.Push(Value(inst.GetSingleWordInOperand(i))); | 
 |             } | 
 |         } else { | 
 |             args.Push(b_.Zero(ty_.u32())); | 
 |         } | 
 |  | 
 |         Emit(b_.Call<spirv::ir::BuiltinCall>(Type(inst.type_id()), fn, args), inst.result_id()); | 
 |     } | 
 |  | 
 |     void EmitImageWrite(const spvtools::opt::Instruction& inst) { | 
 |         auto* image = Value(inst.GetSingleWordInOperand(0)); | 
 |         auto* coord = Value(inst.GetSingleWordInOperand(1)); | 
 |         core::ir::Value* texel = Value(inst.GetSingleWordInOperand(2)); | 
 |  | 
 |         // Our intrinsic has a vec4 type, which matches what WGSL expects. Instead of creating more | 
 |         // intrinsic entries, just turn the texel into a vec4. | 
 |         auto* texel_ty = texel->Type(); | 
 |         if (texel_ty->IsScalar()) { | 
 |             auto* c = b_.Construct(ty_.vec4(texel_ty), texel); | 
 |             EmitWithoutSpvResult(c); | 
 |             texel = c->Result(); | 
 |         } else { | 
 |             auto* vec_ty = texel_ty->As<core::type::Vector>(); | 
 |             TINT_ASSERT(vec_ty); | 
 |  | 
 |             core::ir::Instruction* c = nullptr; | 
 |             if (vec_ty->Width() == 2) { | 
 |                 c = b_.Construct(ty_.vec4(vec_ty->Type()), texel, b_.Zero(vec_ty)); | 
 |             } else if (vec_ty->Width() == 3) { | 
 |                 c = b_.Construct(ty_.vec4(vec_ty->Type()), texel, b_.Zero(vec_ty->Type())); | 
 |             } | 
 |             if (c != nullptr) { | 
 |                 EmitWithoutSpvResult(c); | 
 |                 texel = c->Result(); | 
 |             } | 
 |         } | 
 |  | 
 |         Vector<core::ir::Value*, 4> args = {image, coord, texel}; | 
 |         if (inst.NumInOperands() > 3) { | 
 |             uint32_t literal_mask = inst.GetSingleWordInOperand(3); | 
 |             args.Push(b_.Constant(u32(literal_mask))); | 
 |             TINT_ASSERT(literal_mask == 0); | 
 |         } else { | 
 |             args.Push(b_.Zero(ty_.u32())); | 
 |         } | 
 |  | 
 |         Emit(b_.Call<spirv::ir::BuiltinCall>(ty_.void_(), spirv::BuiltinFn::kImageWrite, args), | 
 |              inst.result_id()); | 
 |     } | 
 |  | 
 |     void EmitImageQuery(const spvtools::opt::Instruction& inst, spirv::BuiltinFn fn) { | 
 |         auto* image = Value(inst.GetSingleWordInOperand(0)); | 
 |  | 
 |         auto* ty = Type(inst.type_id()); | 
 |         Emit(b_.CallExplicit<spirv::ir::BuiltinCall>(ty, fn, Vector{ty->DeepestElement()}, image), | 
 |              inst.result_id()); | 
 |     } | 
 |  | 
 |     void EmitImageQuerySizeLod(const spvtools::opt::Instruction& inst) { | 
 |         auto* image = Value(inst.GetSingleWordInOperand(0)); | 
 |         auto* level = Value(inst.GetSingleWordInOperand(1)); | 
 |  | 
 |         auto* ty = Type(inst.type_id()); | 
 |         Emit(b_.CallExplicit<spirv::ir::BuiltinCall>(ty, spirv::BuiltinFn::kImageQuerySizeLod, | 
 |                                                      Vector{ty->DeepestElement()}, image, level), | 
 |              inst.result_id()); | 
 |     } | 
 |  | 
 |     void EmitAtomicSigned(const spvtools::opt::Instruction& inst, spirv::BuiltinFn fn) { | 
 |         core::ir::Value* v = Value(inst.GetSingleWordOperand(2)); | 
 |         TINT_ASSERT(v->Type()->UnwrapPtr()->Is<core::type::I32>()); | 
 |         EmitSpirvBuiltinCall(inst, fn); | 
 |     } | 
 |  | 
 |     void EmitAtomicUnsigned(const spvtools::opt::Instruction& inst, spirv::BuiltinFn fn) { | 
 |         core::ir::Value* v = Value(inst.GetSingleWordOperand(2)); | 
 |         TINT_ASSERT(v->Type()->UnwrapPtr()->Is<core::type::U32>()); | 
 |         EmitSpirvBuiltinCall(inst, fn); | 
 |     } | 
 |  | 
 |     void EmitArrayLength(const spvtools::opt::Instruction& inst) { | 
 |         auto strct = Value(inst.GetSingleWordInOperand(0)); | 
 |         auto field_index = inst.GetSingleWordInOperand(1); | 
 |  | 
 |         auto* ptr = strct->Type()->As<core::type::Pointer>(); | 
 |         TINT_ASSERT(ptr); | 
 |  | 
 |         auto* ty = ptr->StoreType()->As<core::type::Struct>(); | 
 |         TINT_ASSERT(ty); | 
 |  | 
 |         auto* access = | 
 |             b_.Access(ty_.ptr(ptr->AddressSpace(), ty->Members().Back()->Type(), ptr->Access()), | 
 |                       strct, u32(field_index)); | 
 |         EmitWithoutSpvResult(access); | 
 |  | 
 |         Emit(b_.Call(Type(inst.type_id()), core::BuiltinFn::kArrayLength, Vector{access->Result()}), | 
 |              inst.result_id()); | 
 |     } | 
 |  | 
 |     void EmitControlBarrier(const spvtools::opt::Instruction& inst) { | 
 |         auto get_constant = [&](uint32_t idx) { | 
 |             uint32_t id = inst.GetSingleWordOperand(idx); | 
 |             if (auto* constant = spirv_context_->get_constant_mgr()->FindDeclaredConstant(id)) { | 
 |                 return constant->GetU32(); | 
 |             } | 
 |             TINT_ICE() << "invalid or missing operands for control barrier"; | 
 |         }; | 
 |  | 
 |         uint32_t execution = get_constant(0); | 
 |         uint32_t memory = get_constant(1); | 
 |         uint32_t semantics = get_constant(2); | 
 |  | 
 |         if (execution != uint32_t(spv::Scope::Workgroup)) { | 
 |             TINT_ICE() << "unsupported control barrier execution scope: " | 
 |                        << "expected Workgroup (2), got: " << execution; | 
 |         } | 
 |  | 
 |         if (semantics & uint32_t(spv::MemorySemanticsMask::AcquireRelease)) { | 
 |             semantics &= ~static_cast<uint32_t>(spv::MemorySemanticsMask::AcquireRelease); | 
 |         } else { | 
 |             TINT_ICE() << "control barrier semantics requires acquire and release"; | 
 |         } | 
 |         if (memory != uint32_t(spv::Scope::Workgroup)) { | 
 |             TINT_ICE() << "control barrier requires workgroup memory scope"; | 
 |         } | 
 |  | 
 |         if (semantics & uint32_t(spv::MemorySemanticsMask::WorkgroupMemory)) { | 
 |             EmitWithoutSpvResult(b_.Call(ty_.void_(), core::BuiltinFn::kWorkgroupBarrier)); | 
 |             semantics &= ~static_cast<uint32_t>(spv::MemorySemanticsMask::WorkgroupMemory); | 
 |         } | 
 |  | 
 |         if (semantics & uint32_t(spv::MemorySemanticsMask::UniformMemory)) { | 
 |             EmitWithoutSpvResult(b_.Call(ty_.void_(), core::BuiltinFn::kStorageBarrier)); | 
 |             semantics &= ~static_cast<uint32_t>(spv::MemorySemanticsMask::UniformMemory); | 
 |         } | 
 |  | 
 |         if (semantics & uint32_t(spv::MemorySemanticsMask::ImageMemory)) { | 
 |             EmitWithoutSpvResult(b_.Call(ty_.void_(), core::BuiltinFn::kTextureBarrier)); | 
 |             semantics &= ~static_cast<uint32_t>(spv::MemorySemanticsMask::ImageMemory); | 
 |         } | 
 |  | 
 |         if (semantics) { | 
 |             TINT_ICE() << "unsupported control barrier semantics: " << semantics; | 
 |         } | 
 |     } | 
 |  | 
 |     void CheckAtomicNotFloat(const spvtools::opt::Instruction& inst) { | 
 |         auto* ty = Type(inst.type_id()); | 
 |         if (ty->IsFloatScalar()) { | 
 |             TINT_ICE() << "Atomic operations on floating point values not supported."; | 
 |         } | 
 |     } | 
 |  | 
 |     void EmitAtomicStore(const spvtools::opt::Instruction& inst) { | 
 |         auto* v = Value(inst.GetSingleWordInOperand(0)); | 
 |         auto* ty = v->Type()->UnwrapPtr(); | 
 |         if (ty->IsFloatScalar()) { | 
 |             TINT_ICE() << "Atomic operations on floating point values not supported."; | 
 |         } | 
 |  | 
 |         EmitWithoutSpvResult(b_.Call<spirv::ir::BuiltinCall>( | 
 |             ty_.void_(), spirv::BuiltinFn::kAtomicStore, Args(inst, 0))); | 
 |     } | 
 |  | 
 |     void EmitBitcast(const spvtools::opt::Instruction& inst) { | 
 |         auto val = Value(inst.GetSingleWordInOperand(0)); | 
 |         auto ty = Type(inst.type_id()); | 
 |         Emit(b_.Bitcast(ty, val), inst.result_id()); | 
 |     } | 
 |  | 
 |     core::ir::ControlInstruction* StopWalkingAt(uint32_t id) { | 
 |         auto iter = walk_stop_blocks_.find(id); | 
 |         if (iter != walk_stop_blocks_.end()) { | 
 |             return iter->second; | 
 |         } | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     core::ir::Loop* ContinueTarget(uint32_t id) { | 
 |         auto iter = continue_targets_.find(id); | 
 |         if (iter != continue_targets_.end()) { | 
 |             return iter->second; | 
 |         } | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     void EmitBranch(const spvtools::opt::Instruction& inst) { | 
 |         auto dest_id = inst.GetSingleWordInOperand(0); | 
 |  | 
 |         // Disallow fallthrough | 
 |         for (auto& switch_blocks : current_switch_blocks_) { | 
 |             if (switch_blocks.count(dest_id) != 0) { | 
 |                 TINT_ICE() << "switch fallthrough not supported by the SPIR-V reader"; | 
 |             } | 
 |         } | 
 |  | 
 |         // The destination is a continuing block, so insert a `continue` | 
 |         if (auto* loop = ContinueTarget(dest_id)) { | 
 |             EmitWithoutResult(b_.Continue(loop)); | 
 |             return; | 
 |         } | 
 |         // If this is branching to a previous merge block then we're done. It can be a previous | 
 |         // merge block in the case of an `if` breaking out of a `switch` or `loop`. | 
 |         if (auto* ctrl_inst = StopWalkingAt(dest_id)) { | 
 |             if (auto* loop = ctrl_inst->As<core::ir::Loop>()) { | 
 |                 // Going to the merge in a loop body has to be a break regardless of nesting level. | 
 |  | 
 |                 if (InBlock(loop->Body()) && !InBlock(loop->Continuing())) { | 
 |                     EmitWithoutResult(b_.Exit(ctrl_inst)); | 
 |                 } | 
 |             } else if (ctrl_inst->Is<core::ir::Switch>()) { | 
 |                 EmitWithoutResult(b_.Exit(ctrl_inst)); | 
 |             } | 
 |             return; | 
 |         } | 
 |  | 
 |         TINT_ASSERT(current_spirv_function_); | 
 |         const auto& bb = current_spirv_function_->FindBlock(dest_id); | 
 |  | 
 |         EmitBlock(current_block_, *bb); | 
 |     } | 
 |  | 
 |     // Given a true and false branch find if there is a common convergence point before the merge | 
 |     // block. | 
 |     std::optional<uint32_t> FindPremergeId(uint32_t true_id, | 
 |                                            uint32_t false_id, | 
 |                                            std::optional<uint32_t> merge_id) { | 
 |         auto* cfg = spirv_context_->cfg(); | 
 |  | 
 |         // We need a merge block, the true and false to be unique and the true and false to not be | 
 |         // the merge. | 
 |         if (!merge_id || true_id == false_id || true_id == merge_id || false_id == merge_id) { | 
 |             return std::nullopt; | 
 |         } | 
 |  | 
 |         // Get the list of blocks from the true branch to the merge | 
 |         std::list<spvtools::opt::BasicBlock*> true_blocks; | 
 |         cfg->ComputeStructuredOrder( | 
 |             current_spirv_function_, &*(current_spirv_function_->FindBlock(true_id)), | 
 |             &*(current_spirv_function_->FindBlock(merge_id.value())), &true_blocks); | 
 |  | 
 |         // Get the list of blocks from the false branch to the merge | 
 |         std::list<spvtools::opt::BasicBlock*> false_blocks; | 
 |         cfg->ComputeStructuredOrder( | 
 |             current_spirv_function_, &*(current_spirv_function_->FindBlock(false_id)), | 
 |             &*(current_spirv_function_->FindBlock(merge_id.value())), &false_blocks); | 
 |  | 
 |         auto& true_end = true_blocks.back(); | 
 |         auto& false_end = false_blocks.back(); | 
 |  | 
 |         // We only consider the block as returning if it didn't return through | 
 |         // the merge block. (I.e. it's a direct exit from inside the branch | 
 |         // itself. | 
 |         bool true_returns = true_end->id() != merge_id && true_end->IsReturn(); | 
 |         bool false_returns = false_end->id() != merge_id && false_end->IsReturn(); | 
 |         // If one of the blocks returns but the other doesn't, then we can't | 
 |         // have a premerge block. | 
 |         if (true_returns != false_returns) { | 
 |             return std::nullopt; | 
 |         } | 
 |  | 
 |         // If they don't return, both blocks must merge to the same place. | 
 |         if (!true_returns && (true_end->id() != false_end->id())) { | 
 |             return std::nullopt; | 
 |         } | 
 |  | 
 |         // If these aren't returns, then remove the merge blocks. | 
 |         if (!true_returns) { | 
 |             true_blocks.pop_back(); | 
 |             false_blocks.pop_back(); | 
 |         } | 
 |  | 
 |         std::optional<uint32_t> id = std::nullopt; | 
 |         while (!true_blocks.empty() && !false_blocks.empty()) { | 
 |             auto* tb = true_blocks.back(); | 
 |             if (tb != false_blocks.back()) { | 
 |                 break; | 
 |             } | 
 |  | 
 |             id = tb->id(); | 
 |  | 
 |             true_blocks.pop_back(); | 
 |             false_blocks.pop_back(); | 
 |         } | 
 |  | 
 |         // If this is already a stop block, so it can't be a premerge | 
 |         if (id.has_value() && walk_stop_blocks_.contains(id.value())) { | 
 |             return std::nullopt; | 
 |         } | 
 |         return id; | 
 |     } | 
 |  | 
 |     core::ir::ControlInstruction* ExitFor(core::ir::ControlInstruction* ctrl, | 
 |                                           core::ir::ControlInstruction* parent) { | 
 |         // If you have a BranchConditional inside a BranchConditional where | 
 |         // the inner does not have a merge block, it can branch out to the | 
 |         // merge of the outer conditional. But, WGSL doesn't allow that, so | 
 |         // just treat it as an exit of the inner block. | 
 |         if (ctrl->Is<core::ir::If>() && parent->Is<core::ir::If>()) { | 
 |             return parent; | 
 |         } | 
 |         return ctrl; | 
 |     } | 
 |  | 
 |     core::ir::Instruction* EmitBranchStopBlock(core::ir::ControlInstruction* ctrl, | 
 |                                                core::ir::If* if_, | 
 |                                                core::ir::Block* blk, | 
 |                                                uint32_t target) { | 
 |         if (auto* loop = ContinueTarget(target)) { | 
 |             auto* cont = b_.Continue(loop); | 
 |             blk->Append(cont); | 
 |             return cont; | 
 |         } | 
 |  | 
 |         auto iter = merge_to_premerge_.find(target); | 
 |         if (iter != merge_to_premerge_.end()) { | 
 |             // Branch to a merge block, but skipping over an expected premerge block | 
 |             // so we need a guard. | 
 |             if (!iter->second.condition) { | 
 |                 b_.InsertBefore(iter->second.parent, | 
 |                                 [&] { iter->second.condition = b_.Var("execute_premerge", true); }); | 
 |             } | 
 |             b_.Append(blk, [&] { b_.Store(iter->second.condition, false); }); | 
 |         } | 
 |  | 
 |         auto* exit = b_.Exit(ExitFor(ctrl, if_)); | 
 |         blk->Append(exit); | 
 |         return exit; | 
 |     } | 
 |  | 
 |     bool ProcessBranchAsLoopHeader(core::ir::Value* cond, uint32_t true_id, uint32_t false_id) { | 
 |         bool true_is_header = loop_headers_.count(true_id) > 0; | 
 |         bool false_is_header = loop_headers_.count(false_id) > 0; | 
 |  | 
 |         if (!true_is_header && !false_is_header) { | 
 |             return false; | 
 |         } | 
 |  | 
 |         core::ir::Loop* loop = nullptr; | 
 |         uint32_t merge_id = 0; | 
 |  | 
 |         if (true_is_header) { | 
 |             const auto& bb_header = current_spirv_function_->FindBlock(true_id); | 
 |             merge_id = (*bb_header).MergeBlockIdIfAny(); | 
 |  | 
 |             loop = loop_headers_[true_id]; | 
 |  | 
 |         } else { | 
 |             const auto& bb_header = current_spirv_function_->FindBlock(false_id); | 
 |             merge_id = (*bb_header).MergeBlockIdIfAny(); | 
 |  | 
 |             loop = loop_headers_[false_id]; | 
 |         } | 
 |         TINT_ASSERT(merge_id > 0); | 
 |  | 
 |         // The only time a loop continuing will be in current blocks is if | 
 |         // we're inside the continuing block itself. | 
 |         // | 
 |         // Note, we may _not_ be in the IR continuing block. This can happen | 
 |         // in the case of a SPIR-V loop where the header_id and continue_id | 
 |         // are the same. We'll be emitting into the IR body, but branch to | 
 |         // the header because that's also the continuing in SPIR-V. | 
 |         if (current_blocks_.count(loop->Continuing()) != 0u) { | 
 |             if (true_id == merge_id && false_is_header) { | 
 |                 EmitWithoutResult(b_.BreakIf(loop, cond)); | 
 |                 return true; | 
 |             } | 
 |             if (false_id == merge_id && true_is_header) { | 
 |                 auto* val = b_.Not(cond->Type(), cond); | 
 |                 EmitWithoutSpvResult(val); | 
 |                 EmitWithoutResult(b_.BreakIf(loop, val)); | 
 |                 return true; | 
 |             } | 
 |         } | 
 |         return false; | 
 |     } | 
 |  | 
 |     void EmitPremergeBlock(uint32_t merge_id, | 
 |                            uint32_t premerge_start_id, | 
 |                            core::ir::If* premerge_if_) { | 
 |         auto iter = merge_to_premerge_.find(merge_id); | 
 |         TINT_ASSERT(iter != merge_to_premerge_.end()); | 
 |  | 
 |         // If we created a condition guard, we need to swap the premerge `true` condition with | 
 |         // the condition variable. | 
 |         if (iter->second.condition) { | 
 |             auto* premerge_cond = b_.Load(iter->second.condition); | 
 |             EmitWithoutSpvResult(premerge_cond); | 
 |             premerge_if_->SetOperand(core::ir::If::kConditionOperandOffset, | 
 |                                      premerge_cond->Result()); | 
 |         } | 
 |         merge_to_premerge_.erase(iter); | 
 |  | 
 |         EmitWithoutResult(premerge_if_); | 
 |  | 
 |         const auto& bb_premerge = current_spirv_function_->FindBlock(premerge_start_id); | 
 |         EmitBlockParent(premerge_if_->True(), *bb_premerge); | 
 |         if (!premerge_if_->True()->Terminator()) { | 
 |             premerge_if_->True()->Append(b_.Exit(premerge_if_)); | 
 |         } | 
 |  | 
 |         premerge_if_->False()->Append(b_.Unreachable()); | 
 |     } | 
 |  | 
 |     void EmitIfBranch(uint32_t id, core::ir::If* if_, core::ir::Block* blk) { | 
 |         const auto& bb = current_spirv_function_->FindBlock(id); | 
 |         EmitBlockParent(blk, *bb); | 
 |         if (!blk->Terminator()) { | 
 |             blk->Append(b_.Exit(if_)); | 
 |         } | 
 |     } | 
 |  | 
 |     void EmitBranchConditional(const spvtools::opt::BasicBlock& bb, | 
 |                                const spvtools::opt::Instruction& inst) { | 
 |         auto cond = Value(inst.GetSingleWordInOperand(0)); | 
 |         auto true_id = inst.GetSingleWordInOperand(1); | 
 |         auto false_id = inst.GetSingleWordInOperand(2); | 
 |  | 
 |         if (ProcessBranchAsLoopHeader(cond, true_id, false_id)) { | 
 |             return; | 
 |         } | 
 |  | 
 |         // If the true and false block are the same, then we change the condition into | 
 |         // `cond || true` so that we always take the true block, the false block will be marked | 
 |         // unreachable. | 
 |         if (true_id == false_id) { | 
 |             auto* binary = b_.Binary(core::BinaryOp::kOr, cond->Type(), cond, b_.Constant(true)); | 
 |             EmitWithoutSpvResult(binary); | 
 |             cond = binary->Result(); | 
 |         } | 
 |  | 
 |         auto* if_ = b_.If(cond); | 
 |         EmitWithoutResult(if_); | 
 |  | 
 |         std::optional<uint32_t> merge_id = std::nullopt; | 
 |  | 
 |         auto* merge_inst = bb.GetMergeInst(); | 
 |         if (bb.GetLoopMergeInst()) { | 
 |             // If this is a loop merge block, then the merge instruction is for | 
 |             // the loop, not the branch conditional. | 
 |             merge_inst = nullptr; | 
 |         } else if (merge_inst != nullptr) { | 
 |             merge_id = merge_inst->GetSingleWordInOperand(0); | 
 |             walk_stop_blocks_.insert({merge_id.value(), if_}); | 
 |         } | 
 |  | 
 |         TINT_ASSERT(current_spirv_function_); | 
 |  | 
 |         // Determine if there is a premerge block to handle | 
 |         std::optional<uint32_t> premerge_start_id = FindPremergeId(true_id, false_id, merge_id); | 
 |  | 
 |         // If we found the start of a premerge, push it onto the merge stack so this ends up being a | 
 |         // temporary merge block for the if branches. | 
 |         core::ir::If* premerge_if_ = nullptr; | 
 |         if (premerge_start_id.has_value()) { | 
 |             // Must have a merge to have a premerge | 
 |             merge_to_premerge_.insert({merge_id.value(), PremergeInfo{if_, {}}}); | 
 |             premerge_if_ = b_.If(b_.Constant(true)); | 
 |             walk_stop_blocks_.insert({premerge_start_id.value(), premerge_if_}); | 
 |         } | 
 |  | 
 |         if (auto* ctrl = StopWalkingAt(true_id)) { | 
 |             auto* new_inst = EmitBranchStopBlock(ctrl, if_, if_->True(), true_id); | 
 |             inst_to_spirv_block_[new_inst] = bb.id(); | 
 |         } else { | 
 |             EmitIfBranch(true_id, if_, if_->True()); | 
 |         } | 
 |  | 
 |         // Pre-SPIRV 1.6 the true and false blocks could be the same. If that's the case then we | 
 |         // will have changed the condition and the false block is now unreachable. | 
 |         if (false_id == true_id) { | 
 |             if_->False()->Append(b_.Unreachable()); | 
 |         } else if (auto* ctrl = StopWalkingAt(false_id)) { | 
 |             auto* new_inst = EmitBranchStopBlock(ctrl, if_, if_->False(), false_id); | 
 |             inst_to_spirv_block_[new_inst] = bb.id(); | 
 |         } else { | 
 |             EmitIfBranch(false_id, if_, if_->False()); | 
 |         } | 
 |  | 
 |         // There was a premerge, remove it from the merge stack and then emit the premerge into an | 
 |         // `if true` block in order to maintain re-convergence guarantees. The premerge will contain | 
 |         // all the blocks up to the merge block. | 
 |         if (premerge_start_id.has_value()) { | 
 |             EmitPremergeBlock(merge_id.value(), premerge_start_id.value(), premerge_if_); | 
 |         } | 
 |  | 
 |         // Emit the merge block if it exists. | 
 |         if (merge_id.has_value()) { | 
 |             const auto& bb_merge = current_spirv_function_->FindBlock(merge_id.value()); | 
 |             EmitBlock(current_block_, *bb_merge); | 
 |         } | 
 |     } | 
 |  | 
 |     void EmitLoop(const spvtools::opt::BasicBlock& bb) { | 
 |         // This just handles creating the loop itself, the rest of the processing | 
 |         // of the continue and merge blocks will be handled when we deal with the | 
 |         // LoopMerge instruction itself. We have to setup the loop early in order | 
 |         // to capture instructions which come in the header before the LoopMerge. | 
 |         auto* loop = b_.Loop(); | 
 |         EmitWithoutResult(loop); | 
 |  | 
 |         // A `loop` header block can also be the merge block for an `if`. In that the case, replace | 
 |         // the `if` information in the stop blocks with the loop as this must be the `if` merge | 
 |         // block and the `if` is complete. | 
 |         walk_stop_blocks_[bb.id()] = loop; | 
 |     } | 
 |  | 
 |     void EmitLoopMerge(const spvtools::opt::BasicBlock& bb, | 
 |                        const spvtools::opt::Instruction& inst) { | 
 |         auto merge_id = inst.GetSingleWordInOperand(0); | 
 |         auto continue_id = inst.GetSingleWordInOperand(1); | 
 |         auto header_id = bb.id(); | 
 |  | 
 |         // The loop was created in `EmitLoop` and set as the stop block value for | 
 |         // the header block. Retrieve the loop from the stop list. | 
 |         auto* loop = StopWalkingAt(header_id)->As<core::ir::Loop>(); | 
 |         TINT_ASSERT(loop); | 
 |  | 
 |         loop_headers_.insert({header_id, loop}); | 
 |         continue_targets_.insert({continue_id, loop}); | 
 |  | 
 |         // Insert the stop blocks | 
 |         walk_stop_blocks_.insert({merge_id, loop}); | 
 |         if (continue_id != header_id) { | 
 |             walk_stop_blocks_.insert({continue_id, loop}); | 
 |         } | 
 |  | 
 |         // The remainder of the loop body will process when we hit the | 
 |         // BranchConditional or Branch after the LoopMerge. We're already | 
 |         // processing into the loop body from the `EmitLoop` code above so just | 
 |         // continue emitting. | 
 |  | 
 |         // The merge block will be emitted by the `EmitBlock` code after the | 
 |         // instructions in the loop header are emitted. | 
 |     } | 
 |  | 
 |     void EmitSwitch(const spvtools::opt::BasicBlock& bb, const spvtools::opt::Instruction& inst) { | 
 |         auto* selector = Value(inst.GetSingleWordInOperand(0)); | 
 |         auto default_id = inst.GetSingleWordInOperand(1); | 
 |  | 
 |         auto* switch_ = b_.Switch(selector); | 
 |         EmitWithoutResult(switch_); | 
 |  | 
 |         auto* merge_inst = bb.GetMergeInst(); | 
 |         TINT_ASSERT(merge_inst); | 
 |  | 
 |         auto merge_id = merge_inst->GetSingleWordInOperand(0); | 
 |         walk_stop_blocks_.insert({merge_id, switch_}); | 
 |  | 
 |         current_switch_blocks_.push_back({}); | 
 |         auto& switch_blocks = current_switch_blocks_.back(); | 
 |  | 
 |         auto* default_blk = b_.DefaultCase(switch_); | 
 |         if (default_id != merge_id) { | 
 |             switch_blocks.emplace(default_id); | 
 |  | 
 |             const auto& bb_default = current_spirv_function_->FindBlock(default_id); | 
 |             EmitBlockParent(default_blk, *bb_default); | 
 |         } | 
 |         if (!default_blk->Terminator()) { | 
 |             default_blk->Append(b_.ExitSwitch(switch_)); | 
 |         } | 
 |  | 
 |         std::unordered_map<uint32_t, core::ir::Switch::Case*> block_id_to_case; | 
 |         block_id_to_case[default_id] = &(switch_->Cases().Back()); | 
 |  | 
 |         for (uint32_t i = 2; i < inst.NumInOperandWords(); i += 2) { | 
 |             auto blk_id = inst.GetSingleWordInOperand(i + 1); | 
 |  | 
 |             if (blk_id != merge_id) { | 
 |                 switch_blocks.emplace(blk_id); | 
 |             } | 
 |         } | 
 |  | 
 |         // For each selector. | 
 |         for (uint32_t i = 2; i < inst.NumInOperandWords(); i += 2) { | 
 |             auto literal = inst.GetSingleWordInOperand(i); | 
 |             auto blk_id = inst.GetSingleWordInOperand(i + 1); | 
 |  | 
 |             core::ir::Constant* sel = nullptr; | 
 |             if (selector->Type()->Is<core::type::I32>()) { | 
 |                 sel = b_.Constant(i32(literal)); | 
 |             } else { | 
 |                 sel = b_.Constant(u32(literal)); | 
 |             } | 
 |  | 
 |             // Determine if we've seen this block and should combine selectors | 
 |             auto iter = block_id_to_case.find(blk_id); | 
 |             if (iter != block_id_to_case.end()) { | 
 |                 iter->second->selectors.Push(core::ir::Switch::CaseSelector{sel}); | 
 |                 continue; | 
 |             } | 
 |  | 
 |             core::ir::Block* blk = b_.Case(switch_, Vector{sel}); | 
 |             if (blk_id != merge_id) { | 
 |                 const auto& basic_block = current_spirv_function_->FindBlock(blk_id); | 
 |                 EmitBlockParent(blk, *basic_block); | 
 |             } | 
 |             if (!blk->Terminator()) { | 
 |                 blk->Append(b_.ExitSwitch(switch_)); | 
 |             } | 
 |             block_id_to_case[blk_id] = &(switch_->Cases().Back()); | 
 |         } | 
 |  | 
 |         current_switch_blocks_.pop_back(); | 
 |  | 
 |         const auto& bb_merge = current_spirv_function_->FindBlock(merge_id); | 
 |         EmitBlock(current_block_, *bb_merge); | 
 |     } | 
 |  | 
 |     Vector<core::ir::Value*, 4> Args(const spvtools::opt::Instruction& inst, uint32_t start) { | 
 |         Vector<core::ir::Value*, 4> args; | 
 |         for (uint32_t i = start; i < inst.NumOperandWords(); i++) { | 
 |             args.Push(Value(inst.GetSingleWordOperand(i))); | 
 |         } | 
 |         return args; | 
 |     } | 
 |  | 
 |     void EmitBuiltinCall(const spvtools::opt::Instruction& inst, core::BuiltinFn fn) { | 
 |         Emit(b_.Call(Type(inst.type_id()), fn, Args(inst, 2)), inst.result_id()); | 
 |     } | 
 |  | 
 |     void EmitSpirvExplicitBuiltinCall(const spvtools::opt::Instruction& inst, | 
 |                                       spirv::BuiltinFn fn, | 
 |                                       uint32_t first_operand_idx = 2) { | 
 |         Emit(b_.CallExplicit<spirv::ir::BuiltinCall>(Type(inst.type_id()), fn, | 
 |                                                      Vector{Type(inst.type_id())->DeepestElement()}, | 
 |                                                      Args(inst, first_operand_idx)), | 
 |              inst.result_id()); | 
 |     } | 
 |  | 
 |     void EmitSpirvBuiltinCall(const spvtools::opt::Instruction& inst, | 
 |                               spirv::BuiltinFn fn, | 
 |                               uint32_t first_operand_idx = 2) { | 
 |         Emit(b_.Call<spirv::ir::BuiltinCall>(Type(inst.type_id()), fn, | 
 |                                              Args(inst, first_operand_idx)), | 
 |              inst.result_id()); | 
 |     } | 
 |  | 
 |     void EmitBitCount(const spvtools::opt::Instruction& inst) { | 
 |         auto* res_ty = Type(inst.type_id()); | 
 |         Emit(b_.CallExplicit<spirv::ir::BuiltinCall>(res_ty, spirv::BuiltinFn::kBitCount, | 
 |                                                      Vector{res_ty->DeepestElement()}, | 
 |                                                      Args(inst, 2)), | 
 |              inst.result_id()); | 
 |     } | 
 |  | 
 |     /// @param inst the SPIR-V instruction | 
 |     /// Note: This isn't technically correct, but there is no `kill` equivalent in WGSL. The closets | 
 |     /// we have is `discard` which maps to `OpDemoteToHelperInvocation` in SPIR-V. | 
 |     void EmitKill([[maybe_unused]] const spvtools::opt::Instruction& inst) { | 
 |         EmitWithoutResult(b_.Discard()); | 
 |  | 
 |         // An `OpKill` is a terminator in SPIR-V. `discard` is not a terminator in WGSL. After the | 
 |         // `discard` we inject a `return` for the current function. This is similar in spirit to | 
 |         // what `OpKill` does although not totally correct (i.e. we don't early return from calling | 
 |         // functions, just the function where `OpKill` was emitted. There are also limited places in | 
 |         // which `OpKill` can be used. So, we don't have to worry about it in a `continuing` block | 
 |         // because the continuing must end with a branching terminator which `OpKill` does not | 
 |         // branch. | 
 |         if (current_function_->ReturnType()->Is<core::type::Void>()) { | 
 |             EmitWithoutResult(b_.Return(current_function_)); | 
 |         } else { | 
 |             EmitWithoutResult( | 
 |                 b_.Return(current_function_, b_.Zero(current_function_->ReturnType()))); | 
 |         } | 
 |     } | 
 |  | 
 |     /// @param inst the SPIR-V instruction for OpCopyObject | 
 |     void EmitCopyObject(const spvtools::opt::Instruction& inst) { | 
 |         // Make the result Id a pointer to the original copied value. | 
 |         auto* l = b_.Let(Value(inst.GetSingleWordOperand(2))); | 
 |         Emit(l, inst.result_id()); | 
 |     } | 
 |  | 
 |     /// @param inst the SPIR-V instruction for OpCopyMemory | 
 |     void EmitCopyMemory(const spvtools::opt::Instruction& inst) { | 
 |         auto load = b_.Load(Value(inst.GetSingleWordOperand(1))); | 
 |         EmitWithoutSpvResult(load); | 
 |         EmitWithoutResult(b_.Store(Value(inst.GetSingleWordOperand(0)), load)); | 
 |     } | 
 |  | 
 |     /// @param inst the SPIR-V instruction for OpExtInst | 
 |     void EmitExtInst(const spvtools::opt::Instruction& inst) { | 
 |         auto inst_set = inst.GetSingleWordInOperand(0); | 
 |         if (ignored_imports_.count(inst_set) > 0) { | 
 |             // Ignore it but don't error out. | 
 |             return; | 
 |         } | 
 |         if (glsl_std_450_imports_.count(inst_set) > 0) { | 
 |             EmitGlslStd450ExtInst(inst); | 
 |             return; | 
 |         } | 
 |  | 
 |         TINT_UNIMPLEMENTED() << "unhandled extended instruction import with ID " | 
 |                              << inst.GetSingleWordInOperand(0); | 
 |     } | 
 |  | 
 |     // Returns the WGSL standard library function for the given GLSL.std.450 extended instruction | 
 |     // operation code. This handles GLSL functions which directly translate to the WGSL equivalent. | 
 |     // Any non-direct translation is returned as `kNone`. | 
 |     core::BuiltinFn GetGlslStd450WgslEquivalentFuncName(uint32_t ext_opcode) { | 
 |         switch (ext_opcode) { | 
 |             case GLSLstd450Acos: | 
 |                 return core::BuiltinFn::kAcos; | 
 |             case GLSLstd450Acosh: | 
 |                 return core::BuiltinFn::kAcosh; | 
 |             case GLSLstd450Asin: | 
 |                 return core::BuiltinFn::kAsin; | 
 |             case GLSLstd450Asinh: | 
 |                 return core::BuiltinFn::kAsinh; | 
 |             case GLSLstd450Atan: | 
 |                 return core::BuiltinFn::kAtan; | 
 |             case GLSLstd450Atanh: | 
 |                 return core::BuiltinFn::kAtanh; | 
 |             case GLSLstd450Atan2: | 
 |                 return core::BuiltinFn::kAtan2; | 
 |             case GLSLstd450Ceil: | 
 |                 return core::BuiltinFn::kCeil; | 
 |             case GLSLstd450Cos: | 
 |                 return core::BuiltinFn::kCos; | 
 |             case GLSLstd450Cosh: | 
 |                 return core::BuiltinFn::kCosh; | 
 |             case GLSLstd450Cross: | 
 |                 return core::BuiltinFn::kCross; | 
 |             case GLSLstd450Degrees: | 
 |                 return core::BuiltinFn::kDegrees; | 
 |             case GLSLstd450Determinant: | 
 |                 return core::BuiltinFn::kDeterminant; | 
 |             case GLSLstd450Distance: | 
 |                 return core::BuiltinFn::kDistance; | 
 |             case GLSLstd450Exp: | 
 |                 return core::BuiltinFn::kExp; | 
 |             case GLSLstd450Exp2: | 
 |                 return core::BuiltinFn::kExp2; | 
 |             case GLSLstd450FAbs: | 
 |                 return core::BuiltinFn::kAbs; | 
 |             case GLSLstd450FSign: | 
 |                 return core::BuiltinFn::kSign; | 
 |             case GLSLstd450Floor: | 
 |                 return core::BuiltinFn::kFloor; | 
 |             case GLSLstd450Fract: | 
 |                 return core::BuiltinFn::kFract; | 
 |             case GLSLstd450Fma: | 
 |                 return core::BuiltinFn::kFma; | 
 |             case GLSLstd450InverseSqrt: | 
 |                 return core::BuiltinFn::kInverseSqrt; | 
 |             case GLSLstd450Length: | 
 |                 return core::BuiltinFn::kLength; | 
 |             case GLSLstd450Log: | 
 |                 return core::BuiltinFn::kLog; | 
 |             case GLSLstd450Log2: | 
 |                 return core::BuiltinFn::kLog2; | 
 |             case GLSLstd450NClamp: | 
 |             case GLSLstd450FClamp:  // FClamp is less prescriptive about NaN operands | 
 |                 return core::BuiltinFn::kClamp; | 
 |             case GLSLstd450ModfStruct: | 
 |                 return core::BuiltinFn::kModf; | 
 |             case GLSLstd450FrexpStruct: | 
 |                 return core::BuiltinFn::kFrexp; | 
 |             case GLSLstd450NMin: | 
 |             case GLSLstd450FMin:  // FMin is less prescriptive about NaN operands | 
 |                 return core::BuiltinFn::kMin; | 
 |             case GLSLstd450NMax: | 
 |             case GLSLstd450FMax:  // FMax is less prescriptive about NaN operands | 
 |                 return core::BuiltinFn::kMax; | 
 |             case GLSLstd450FMix: | 
 |                 return core::BuiltinFn::kMix; | 
 |             case GLSLstd450PackSnorm4x8: | 
 |                 return core::BuiltinFn::kPack4X8Snorm; | 
 |             case GLSLstd450PackUnorm4x8: | 
 |                 return core::BuiltinFn::kPack4X8Unorm; | 
 |             case GLSLstd450PackSnorm2x16: | 
 |                 return core::BuiltinFn::kPack2X16Snorm; | 
 |             case GLSLstd450PackUnorm2x16: | 
 |                 return core::BuiltinFn::kPack2X16Unorm; | 
 |             case GLSLstd450PackHalf2x16: | 
 |                 return core::BuiltinFn::kPack2X16Float; | 
 |             case GLSLstd450Pow: | 
 |                 return core::BuiltinFn::kPow; | 
 |             case GLSLstd450Radians: | 
 |                 return core::BuiltinFn::kRadians; | 
 |             case GLSLstd450Round: | 
 |             case GLSLstd450RoundEven: | 
 |                 return core::BuiltinFn::kRound; | 
 |             case GLSLstd450Sin: | 
 |                 return core::BuiltinFn::kSin; | 
 |             case GLSLstd450Sinh: | 
 |                 return core::BuiltinFn::kSinh; | 
 |             case GLSLstd450SmoothStep: | 
 |                 return core::BuiltinFn::kSmoothstep; | 
 |             case GLSLstd450Sqrt: | 
 |                 return core::BuiltinFn::kSqrt; | 
 |             case GLSLstd450Step: | 
 |                 return core::BuiltinFn::kStep; | 
 |             case GLSLstd450Tan: | 
 |                 return core::BuiltinFn::kTan; | 
 |             case GLSLstd450Tanh: | 
 |                 return core::BuiltinFn::kTanh; | 
 |             case GLSLstd450Trunc: | 
 |                 return core::BuiltinFn::kTrunc; | 
 |             case GLSLstd450UnpackSnorm4x8: | 
 |                 return core::BuiltinFn::kUnpack4X8Snorm; | 
 |             case GLSLstd450UnpackUnorm4x8: | 
 |                 return core::BuiltinFn::kUnpack4X8Unorm; | 
 |             case GLSLstd450UnpackSnorm2x16: | 
 |                 return core::BuiltinFn::kUnpack2X16Snorm; | 
 |             case GLSLstd450UnpackUnorm2x16: | 
 |                 return core::BuiltinFn::kUnpack2X16Unorm; | 
 |             case GLSLstd450UnpackHalf2x16: | 
 |                 return core::BuiltinFn::kUnpack2X16Float; | 
 |  | 
 |             default: | 
 |                 break; | 
 |         } | 
 |         return core::BuiltinFn::kNone; | 
 |     } | 
 |  | 
 |     spirv::BuiltinFn GetGlslStd450SpirvEquivalentFuncName(uint32_t ext_opcode) { | 
 |         switch (ext_opcode) { | 
 |             case GLSLstd450SAbs: | 
 |                 return spirv::BuiltinFn::kAbs; | 
 |             case GLSLstd450SSign: | 
 |                 return spirv::BuiltinFn::kSign; | 
 |             case GLSLstd450Normalize: | 
 |                 return spirv::BuiltinFn::kNormalize; | 
 |             case GLSLstd450MatrixInverse: | 
 |                 return spirv::BuiltinFn::kInverse; | 
 |             case GLSLstd450SMax: | 
 |                 return spirv::BuiltinFn::kSMax; | 
 |             case GLSLstd450SMin: | 
 |                 return spirv::BuiltinFn::kSMin; | 
 |             case GLSLstd450SClamp: | 
 |                 return spirv::BuiltinFn::kSClamp; | 
 |             case GLSLstd450UMax: | 
 |                 return spirv::BuiltinFn::kUMax; | 
 |             case GLSLstd450UMin: | 
 |                 return spirv::BuiltinFn::kUMin; | 
 |             case GLSLstd450UClamp: | 
 |                 return spirv::BuiltinFn::kUClamp; | 
 |             case GLSLstd450FindILsb: | 
 |                 return spirv::BuiltinFn::kFindILsb; | 
 |             case GLSLstd450FindSMsb: | 
 |                 return spirv::BuiltinFn::kFindSMsb; | 
 |             case GLSLstd450FindUMsb: | 
 |                 return spirv::BuiltinFn::kFindUMsb; | 
 |             case GLSLstd450Refract: | 
 |                 return spirv::BuiltinFn::kRefract; | 
 |             case GLSLstd450Reflect: | 
 |                 return spirv::BuiltinFn::kReflect; | 
 |             case GLSLstd450FaceForward: | 
 |                 return spirv::BuiltinFn::kFaceForward; | 
 |             case GLSLstd450Ldexp: | 
 |                 return spirv::BuiltinFn::kLdexp; | 
 |             case GLSLstd450Modf: | 
 |                 return spirv::BuiltinFn::kModf; | 
 |             case GLSLstd450Frexp: | 
 |                 return spirv::BuiltinFn::kFrexp; | 
 |             default: | 
 |                 break; | 
 |         } | 
 |         return spirv::BuiltinFn::kNone; | 
 |     } | 
 |  | 
 |     Vector<const core::type::Type*, 1> GlslStd450ExplicitParams(uint32_t ext_opcode, | 
 |                                                                 const core::type::Type* result_ty) { | 
 |         if (ext_opcode == GLSLstd450SSign || ext_opcode == GLSLstd450SAbs || | 
 |             ext_opcode == GLSLstd450SMax || ext_opcode == GLSLstd450SMin || | 
 |             ext_opcode == GLSLstd450SClamp || ext_opcode == GLSLstd450UMax || | 
 |             ext_opcode == GLSLstd450UMin || ext_opcode == GLSLstd450UClamp || | 
 |             ext_opcode == GLSLstd450FindILsb || ext_opcode == GLSLstd450FindSMsb || | 
 |             ext_opcode == GLSLstd450FindUMsb) { | 
 |             return {result_ty->DeepestElement()}; | 
 |         } | 
 |         return {}; | 
 |     } | 
 |  | 
 |     /// @param inst the SPIR-V instruction for OpAccessChain | 
 |     void EmitGlslStd450ExtInst(const spvtools::opt::Instruction& inst) { | 
 |         const auto ext_opcode = inst.GetSingleWordInOperand(1); | 
 |         auto* spv_ty = Type(inst.type_id()); | 
 |  | 
 |         Vector<core::ir::Value*, 4> operands; | 
 |         // All parameters to GLSL.std.450 extended instructions are IDs. | 
 |         for (uint32_t idx = 2; idx < inst.NumInOperands(); ++idx) { | 
 |             operands.Push(Value(inst.GetSingleWordInOperand(idx))); | 
 |         } | 
 |  | 
 |         const auto wgsl_fn = GetGlslStd450WgslEquivalentFuncName(ext_opcode); | 
 |         if (wgsl_fn == core::BuiltinFn::kModf) { | 
 |             // For `ModfStruct`, which is, essentially, a WGSL `modf` instruction | 
 |             // we need some special handling. The result type that we produce | 
 |             // must be the SPIR-V type as we don't know how the result is used | 
 |             // later. So, we need to make the WGSL query and re-construct an | 
 |             // object of the right SPIR-V type. We can't, easily, do this later | 
 |             // as we lose the SPIR-V type as soon as we replace the result of the | 
 |             // `modf`. So, inline the work here to generate the correct results. | 
 |  | 
 |             auto* mem_ty = operands[0]->Type(); | 
 |             auto* result_ty = core::type::CreateModfResult(ty_, ir_.symbols, mem_ty); | 
 |  | 
 |             auto* call = b_.Call(result_ty, wgsl_fn, operands); | 
 |             auto* fract = b_.Access(mem_ty, call, 0_u); | 
 |             auto* whole = b_.Access(mem_ty, call, 1_u); | 
 |  | 
 |             EmitWithoutSpvResult(call); | 
 |             EmitWithoutSpvResult(fract); | 
 |             EmitWithoutSpvResult(whole); | 
 |             Emit(b_.Construct(spv_ty, fract, whole), inst.result_id()); | 
 |             return; | 
 |         } | 
 |         if (wgsl_fn == core::BuiltinFn::kFrexp) { | 
 |             // For `FrexpStruct`, which is, essentially, a WGSL `frexp` | 
 |             // instruction we need some special handling. The result type that we | 
 |             // produce must be the SPIR-V type as we don't know how the result is | 
 |             // used later. So, we need to make the WGSL query and re-construct an | 
 |             // object of the right SPIR-V type. We can't, easily, do this later | 
 |             // as we lose the SPIR-V type as soon as we replace the result of the | 
 |             // `frexp`. So, inline the work here to generate the correct results. | 
 |  | 
 |             auto* mem_ty = operands[0]->Type(); | 
 |             auto* result_ty = core::type::CreateFrexpResult(ty_, ir_.symbols, mem_ty); | 
 |  | 
 |             auto* call = b_.Call(result_ty, wgsl_fn, operands); | 
 |             auto* fract = b_.Access(mem_ty, call, 0_u); | 
 |             auto* exp = b_.Access(ty_.MatchWidth(ty_.i32(), mem_ty), call, 1_u); | 
 |             auto* exp_res = exp->Result(); | 
 |  | 
 |             EmitWithoutSpvResult(call); | 
 |             EmitWithoutSpvResult(fract); | 
 |             EmitWithoutSpvResult(exp); | 
 |  | 
 |             if (auto* str = spv_ty->As<core::type::Struct>()) { | 
 |                 auto* exp_ty = str->Members()[1]->Type(); | 
 |                 if (exp_ty->DeepestElement()->IsUnsignedIntegerScalar()) { | 
 |                     auto* uexp = b_.Bitcast(exp_ty, exp); | 
 |                     exp_res = uexp->Result(); | 
 |                     EmitWithoutSpvResult(uexp); | 
 |                 } | 
 |             } | 
 |  | 
 |             Emit(b_.Construct(spv_ty, fract, exp_res), inst.result_id()); | 
 |             return; | 
 |         } | 
 |         if (wgsl_fn != core::BuiltinFn::kNone) { | 
 |             Emit(b_.Call(spv_ty, wgsl_fn, operands), inst.result_id()); | 
 |             return; | 
 |         } | 
 |  | 
 |         const auto spv_fn = GetGlslStd450SpirvEquivalentFuncName(ext_opcode); | 
 |         if (spv_fn != spirv::BuiltinFn::kNone) { | 
 |             auto explicit_params = GlslStd450ExplicitParams(ext_opcode, spv_ty); | 
 |             Emit(b_.CallExplicit<spirv::ir::BuiltinCall>(spv_ty, spv_fn, explicit_params, operands), | 
 |                  inst.result_id()); | 
 |             return; | 
 |         } | 
 |  | 
 |         TINT_UNIMPLEMENTED() << "unhandled GLSL.std.450 instruction " << ext_opcode; | 
 |     } | 
 |  | 
 |     /// @param inst the SPIR-V instruction for OpAccessChain | 
 |     void EmitAccess(const spvtools::opt::Instruction& inst) { | 
 |         Vector indices = Args(inst, 3); | 
 |         auto* base = Value(inst.GetSingleWordOperand(2)); | 
 |  | 
 |         if (indices.IsEmpty()) { | 
 |             // There are no indices, so just forward the base object. | 
 |             AddValue(inst.result_id(), base); | 
 |             return; | 
 |         } | 
 |  | 
 |         // Propagate the access mode of the base object. | 
 |         auto access_mode = core::Access::kUndefined; | 
 |         if (auto* ptr = base->Type()->As<core::type::Pointer>()) { | 
 |             access_mode = ptr->Access(); | 
 |         } | 
 |  | 
 |         auto* access = b_.Access(Type(inst.type_id(), access_mode), base, std::move(indices)); | 
 |         Emit(access, inst.result_id()); | 
 |     } | 
 |  | 
 |     /// @param inst the SPIR-V instruction | 
 |     /// @param op the unary operator to use | 
 |     void EmitUnary(const spvtools::opt::Instruction& inst, | 
 |                    core::UnaryOp op, | 
 |                    uint32_t first_operand_idx = 2) { | 
 |         auto* val = Value(inst.GetSingleWordOperand(first_operand_idx)); | 
 |         auto* unary = b_.Unary(op, Type(inst.type_id()), val); | 
 |         Emit(unary, inst.result_id()); | 
 |     } | 
 |  | 
 |     /// @param inst the SPIR-V instruction | 
 |     /// @param op the binary operator to use | 
 |     void EmitBinary(const spvtools::opt::Instruction& inst, | 
 |                     core::BinaryOp op, | 
 |                     uint32_t first_operand_idx = 2) { | 
 |         auto* lhs = Value(inst.GetSingleWordOperand(first_operand_idx)); | 
 |         auto* rhs = Value(inst.GetSingleWordOperand(first_operand_idx + 1)); | 
 |         auto* binary = b_.Binary(op, Type(inst.type_id()), lhs, rhs); | 
 |         Emit(binary, inst.result_id()); | 
 |     } | 
 |  | 
 |     /// Emits the logical negation of the result of the given SPIR-V instruction. | 
 |     /// @param inst the SPIR-V instruction | 
 |     /// @param op the binary operator to use | 
 |     void EmitInvertedBinary(const spvtools::opt::Instruction& inst, core::BinaryOp op) { | 
 |         auto* lhs = Value(inst.GetSingleWordOperand(2)); | 
 |         auto* rhs = Value(inst.GetSingleWordOperand(3)); | 
 |         auto* binary = b_.Binary(op, Type(inst.type_id()), lhs, rhs); | 
 |         EmitWithoutSpvResult(binary); | 
 |  | 
 |         auto* res = b_.Not(Type(inst.type_id()), binary); | 
 |         Emit(res, inst.result_id()); | 
 |     } | 
 |  | 
 |     /// @param inst the SPIR-V instruction for OpCompositeExtract | 
 |     void EmitCompositeExtract(const spvtools::opt::Instruction& inst) { | 
 |         Vector<core::ir::Value*, 4> indices; | 
 |         for (uint32_t i = 3; i < inst.NumOperandWords(); i++) { | 
 |             indices.Push(b_.Constant(u32(inst.GetSingleWordOperand(i)))); | 
 |         } | 
 |         auto* object = Value(inst.GetSingleWordOperand(2)); | 
 |         auto* access = b_.Access(Type(inst.type_id()), object, std::move(indices)); | 
 |         Emit(access, inst.result_id()); | 
 |     } | 
 |  | 
 |     /// @param inst the SPIR-V instruction for OpCompositeInsert | 
 |     void EmitCompositeInsert(const spvtools::opt::Instruction& inst) { | 
 |         auto* object = Value(inst.GetSingleWordOperand(2)); | 
 |         auto* composite = Value(inst.GetSingleWordOperand(3)); | 
 |         Vector<core::ir::Value*, 4> indices; | 
 |         for (uint32_t i = 4; i < inst.NumOperandWords(); i++) { | 
 |             indices.Push(b_.Constant(u32(inst.GetSingleWordOperand(i)))); | 
 |         } | 
 |  | 
 |         auto* tmp = b_.Var(ty_.ptr(function, Type(inst.type_id()))); | 
 |         tmp->SetInitializer(composite); | 
 |         auto* ptr_ty = ty_.ptr(function, object->Type()); | 
 |         auto* access = b_.Access(ptr_ty, tmp, std::move(indices)); | 
 |  | 
 |         EmitWithoutSpvResult(tmp); | 
 |         EmitWithoutSpvResult(access); | 
 |         EmitWithoutResult(b_.Store(access, object)); | 
 |         Emit(b_.Load(tmp), inst.result_id()); | 
 |     } | 
 |  | 
 |     /// @param inst the SPIR-V instruction for OpCompositeConstruct | 
 |     void EmitConstruct(const spvtools::opt::Instruction& inst) { | 
 |         auto* construct = b_.Construct(Type(inst.type_id()), Args(inst, 2)); | 
 |         Emit(construct, inst.result_id()); | 
 |     } | 
 |  | 
 |     /// @param inst the SPIR-V instruction for OpVectorInsertDynamic | 
 |     void EmitVectorInsertDynamic(const spvtools::opt::Instruction& inst) { | 
 |         auto vector = Value(inst.GetSingleWordOperand(2)); | 
 |         auto component = Value(inst.GetSingleWordOperand(3)); | 
 |         auto index = Value(inst.GetSingleWordOperand(4)); | 
 |         auto* tmp = b_.Var( | 
 |             ty_.ptr(core::AddressSpace::kFunction, Type(inst.type_id()), core::Access::kReadWrite)); | 
 |         tmp->SetInitializer(vector); | 
 |         EmitWithoutSpvResult(tmp); | 
 |         EmitWithoutResult(b_.StoreVectorElement(tmp, index, component)); | 
 |         Emit(b_.Load(tmp), inst.result_id()); | 
 |     } | 
 |  | 
 |     /// @param inst the SPIR-V instruction for OpVectorShuffle | 
 |     void EmitVectorShuffle(const spvtools::opt::Instruction& inst) { | 
 |         auto* vector1 = Value(inst.GetSingleWordOperand(2)); | 
 |         auto* vector2 = Value(inst.GetSingleWordOperand(3)); | 
 |         auto* result_ty = Type(inst.type_id()); | 
 |  | 
 |         uint32_t n1 = vector1->Type()->As<core::type::Vector>()->Width(); | 
 |         uint32_t n2 = vector2->Type()->As<core::type::Vector>()->Width(); | 
 |  | 
 |         Vector<uint32_t, 4> literals; | 
 |         for (uint32_t i = 4; i < inst.NumOperandWords(); i++) { | 
 |             literals.Push(inst.GetSingleWordOperand(i)); | 
 |         } | 
 |  | 
 |         // Check if all literals fall entirely within `vector1` or `vector2`, | 
 |         // which would allow us to use a single-vector swizzle. | 
 |         bool swizzle_from_vector1_only = true; | 
 |         bool swizzle_from_vector2_only = true; | 
 |         for (auto& literal : literals) { | 
 |             if (literal == ~0u) { | 
 |                 // A `0xFFFFFFFF` literal represents an undefined index, | 
 |                 // fallback to first index. | 
 |                 literal = 0; | 
 |             } | 
 |             if (literal >= n1) { | 
 |                 swizzle_from_vector1_only = false; | 
 |             } | 
 |             if (literal < n1) { | 
 |                 swizzle_from_vector2_only = false; | 
 |             } | 
 |         } | 
 |  | 
 |         // If only one vector is used, we can swizzle it. | 
 |         if (swizzle_from_vector1_only) { | 
 |             // Indices are already within `[0, n1)`, as expected by `Swizzle` IR | 
 |             // for `vector1`. | 
 |             Emit(b_.Swizzle(result_ty, vector1, literals), inst.result_id()); | 
 |             return; | 
 |         } | 
 |         if (swizzle_from_vector2_only) { | 
 |             // Map logical concatenated indices' range `[n1, n1 + n2)` into the range | 
 |             // `[0, n2)`, as expected by `Swizzle` IR for `vector2`. | 
 |             for (auto& literal : literals) { | 
 |                 literal -= n1; | 
 |             } | 
 |             Emit(b_.Swizzle(result_ty, vector2, literals), inst.result_id()); | 
 |             return; | 
 |         } | 
 |  | 
 |         // Swizzle is not possible, construct the result vector out of elements | 
 |         // from both vectors. | 
 |         auto* element_ty = vector1->Type()->DeepestElement(); | 
 |         Vector<core::ir::Value*, 4> result; | 
 |         for (auto idx : literals) { | 
 |             TINT_ASSERT(idx < n1 + n2); | 
 |  | 
 |             if (idx < n1) { | 
 |                 auto* access_inst = b_.Access(element_ty, vector1, b_.Constant(u32(idx))); | 
 |                 EmitWithoutSpvResult(access_inst); | 
 |                 result.Push(access_inst->Result()); | 
 |             } else { | 
 |                 auto* access_inst = b_.Access(element_ty, vector2, b_.Constant(u32(idx - n1))); | 
 |                 EmitWithoutSpvResult(access_inst); | 
 |                 result.Push(access_inst->Result()); | 
 |             } | 
 |         } | 
 |  | 
 |         Emit(b_.Construct(result_ty, result), inst.result_id()); | 
 |     } | 
 |  | 
 |     /// @param inst the SPIR-V instruction for OpFunctionCall | 
 |     void EmitFunctionCall(const spvtools::opt::Instruction& inst) { | 
 |         Emit(b_.Call(Function(inst.GetSingleWordInOperand(0)), Args(inst, 3)), inst.result_id()); | 
 |     } | 
 |  | 
 |     /// @param inst the SPIR-V instruction for OpVariable | 
 |     void EmitVar(const spvtools::opt::Instruction& inst) { | 
 |         // Handle decorations. | 
 |         std::optional<uint32_t> group; | 
 |         std::optional<uint32_t> binding; | 
 |         core::Access access_mode = core::Access::kUndefined; | 
 |         core::IOAttributes io_attributes; | 
 |         auto interpolation = [&]() -> core::Interpolation& { | 
 |             // Create the interpolation field with the default values on first call. | 
 |             if (!io_attributes.interpolation.has_value()) { | 
 |                 io_attributes.interpolation = core::Interpolation{ | 
 |                     .type = core::InterpolationType::kPerspective, | 
 |                     .sampling = core::InterpolationSampling::kUndefined, | 
 |                 }; | 
 |             } | 
 |             return io_attributes.interpolation.value(); | 
 |         }; | 
 |         for (auto* deco : | 
 |              spirv_context_->get_decoration_mgr()->GetDecorationsFor(inst.result_id(), false)) { | 
 |             auto d = deco->GetSingleWordOperand(1); | 
 |             switch (spv::Decoration(d)) { | 
 |                 case spv::Decoration::RelaxedPrecision:  // WGSL is relaxed precision by default | 
 |                     break; | 
 |                 case spv::Decoration::NonReadable: | 
 |                     access_mode = core::Access::kWrite; | 
 |                     break; | 
 |                 case spv::Decoration::NonWritable: | 
 |                     access_mode = core::Access::kRead; | 
 |                     break; | 
 |                 case spv::Decoration::DescriptorSet: | 
 |                     group = deco->GetSingleWordOperand(2); | 
 |                     break; | 
 |                 case spv::Decoration::Binding: | 
 |                     binding = deco->GetSingleWordOperand(2); | 
 |                     break; | 
 |                 case spv::Decoration::BuiltIn: | 
 |                     io_attributes.builtin = Builtin(spv::BuiltIn(deco->GetSingleWordOperand(2))); | 
 |                     break; | 
 |                 case spv::Decoration::Invariant: | 
 |                     io_attributes.invariant = true; | 
 |                     break; | 
 |                 case spv::Decoration::Location: | 
 |                     io_attributes.location = deco->GetSingleWordOperand(2); | 
 |                     break; | 
 |                 case spv::Decoration::NoPerspective: | 
 |                     interpolation().type = core::InterpolationType::kLinear; | 
 |                     break; | 
 |                 case spv::Decoration::Flat: | 
 |                     interpolation().type = core::InterpolationType::kFlat; | 
 |                     break; | 
 |                 case spv::Decoration::Centroid: | 
 |                     interpolation().sampling = core::InterpolationSampling::kCentroid; | 
 |                     break; | 
 |                 case spv::Decoration::Sample: | 
 |                     interpolation().sampling = core::InterpolationSampling::kSample; | 
 |                     break; | 
 |                 case spv::Decoration::Index: | 
 |                     io_attributes.blend_src = deco->GetSingleWordOperand(2); | 
 |                     break; | 
 |                 case spv::Decoration::Coherent: | 
 |                     // Tint has coherent memory semantics, so this is a no-op. | 
 |                     break; | 
 |                 default: | 
 |                     TINT_UNIMPLEMENTED() << "unhandled decoration " << d; | 
 |             } | 
 |         } | 
 |  | 
 |         if (io_attributes.interpolation.has_value()) { | 
 |             // WGSL requires that '@interpolate(flat)' needs to be paired with '@location', however | 
 |             // SPIR-V requires all fragment shader integer Inputs are 'flat'. If the decorations do | 
 |             // not contain a spv::Decoration::Location, then remove the interpolation decoration. | 
 |             // | 
 |             // The `perspective,center` interpolation is the default value if one isn't provided. | 
 |             // Just strip it off. This keeps us from accidentally applying interpolation where it | 
 |             // isn't permitted, and it isn't necessary. | 
 |             if ((io_attributes.interpolation->type == core::InterpolationType::kFlat && | 
 |                  !io_attributes.location.has_value()) || | 
 |                 (io_attributes.interpolation->type == core::InterpolationType::kPerspective && | 
 |                  io_attributes.interpolation->sampling == core::InterpolationSampling::kCenter)) { | 
 |                 io_attributes.interpolation = std::nullopt; | 
 |             } | 
 |         } | 
 |  | 
 |         auto* element_ty = Type(inst.type_id(), access_mode)->As<core::type::Pointer>(); | 
 |         auto* var = b_.Var(element_ty); | 
 |         if (inst.NumOperands() > 3) { | 
 |             var->SetInitializer(Value(inst.GetSingleWordOperand(3))); | 
 |         } | 
 |  | 
 |         if (group || binding) { | 
 |             TINT_ASSERT(group && binding); | 
 |  | 
 |             // Remap any samplers which match an entry in the sampler mappings | 
 |             // table. | 
 |             if (element_ty->StoreType()->Is<core::type::Sampler>()) { | 
 |                 auto it = | 
 |                     options_.sampler_mappings.find(BindingPoint{group.value(), binding.value()}); | 
 |                 if (it != options_.sampler_mappings.end()) { | 
 |                     auto bp = it->second; | 
 |                     group = bp.group; | 
 |                     binding = bp.binding; | 
 |                 } | 
 |             } | 
 |  | 
 |             auto& grp = max_binding.GetOrAddZero(group.value()); | 
 |             grp = std::max(grp, binding.value()); | 
 |  | 
 |             auto& used = used_bindings.GetOrAddZero(BindingPoint{group.value(), binding.value()}); | 
 |             used += 1; | 
 |  | 
 |             io_attributes.binding_point = {group.value(), binding.value()}; | 
 |         } | 
 |         var->SetAttributes(std::move(io_attributes)); | 
 |         var_to_original_access_mode_.insert({var, access_mode}); | 
 |  | 
 |         Emit(var, inst.result_id()); | 
 |     } | 
 |  | 
 |   private: | 
 |     /// TypeKey describes a SPIR-V type with an access mode. | 
 |     struct TypeKey { | 
 |         /// The SPIR-V type object. | 
 |         const spvtools::opt::analysis::Type* type; | 
 |         /// The access mode. | 
 |         core::Access access_mode; | 
 |  | 
 |         // Equality operator for TypeKey. | 
 |         bool operator==(const TypeKey& other) const { | 
 |             return type == other.type && access_mode == other.access_mode; | 
 |         } | 
 |  | 
 |         /// @returns the hash code of the TypeKey | 
 |         tint::HashCode HashCode() const { return Hash(type, access_mode); } | 
 |     }; | 
 |  | 
 |     /// The parser options | 
 |     const Options& options_; | 
 |  | 
 |     /// The generated IR module. | 
 |     core::ir::Module ir_; | 
 |     /// The Tint IR builder. | 
 |     core::ir::Builder b_{ir_}; | 
 |     /// The Tint type manager. | 
 |     core::type::Manager& ty_{ir_.Types()}; | 
 |  | 
 |     /// The Tint IR function that is currently being emitted. | 
 |     core::ir::Function* current_function_ = nullptr; | 
 |     /// The Tint IR block that is currently being emitted. | 
 |     core::ir::Block* current_block_ = nullptr; | 
 |     /// A map from a SPIR-V type declaration to the corresponding Tint type object. | 
 |     Hashmap<TypeKey, const core::type::Type*, 16> types_; | 
 |     /// A map from a SPIR-V function definition result ID to the corresponding Tint function object. | 
 |     Hashmap<uint32_t, core::ir::Function*, 8> functions_; | 
 |     /// A map from a SPIR-V result ID to the corresponding Tint value object. | 
 |     Hashmap<uint32_t, core::ir::Value*, 8> values_; | 
 |     /// Maps a `group` number to the largest seen `binding` value for that group | 
 |     Hashmap<uint32_t, uint32_t, 4> max_binding; | 
 |     /// A map of binding point to the count of usages | 
 |     Hashmap<BindingPoint, uint32_t, 4> used_bindings; | 
 |  | 
 |     /// The SPIR-V context containing the SPIR-V tools intermediate representation. | 
 |     std::unique_ptr<spvtools::opt::IRContext> spirv_context_; | 
 |     /// The current SPIR-V function being emitted | 
 |     spvtools::opt::Function* current_spirv_function_ = nullptr; | 
 |  | 
 |     // The set of IDs that are imports of the GLSL.std.450 extended instruction sets. | 
 |     std::unordered_set<uint32_t> glsl_std_450_imports_; | 
 |     // The set of IDs of imports that are ignored. For example, any "NonSemanticInfo." import is | 
 |     // ignored. | 
 |     std::unordered_set<uint32_t> ignored_imports_; | 
 |  | 
 |     // Map of SPIR-V IDs to string names | 
 |     std::unordered_map<uint32_t, std::string> id_to_name_; | 
 |     // Map of SPIR-V Struct IDs to a list of member string names | 
 |     std::unordered_map<uint32_t, std::vector<std::string>> struct_to_member_names_; | 
 |  | 
 |     // Set of SPIR-V block ids where we'll stop a `Branch` instruction walk. These could be merge | 
 |     // blocks, premerge blocks, continuing blocks, etc. | 
 |     std::unordered_map<uint32_t, core::ir::ControlInstruction*> walk_stop_blocks_; | 
 |     // Map of continue target ID to the controlling IR loop. | 
 |     std::unordered_map<uint32_t, core::ir::Loop*> continue_targets_; | 
 |     // Map of header target ID to the controlling IR loop. | 
 |     std::unordered_map<uint32_t, core::ir::Loop*> loop_headers_; | 
 |  | 
 |     struct PremergeInfo { | 
 |         core::ir::If* parent = nullptr; | 
 |         core::ir::Var* condition = nullptr; | 
 |     }; | 
 |     // Map of merge ID to an associated premerge_id, if any | 
 |     std::unordered_map<uint32_t, PremergeInfo> merge_to_premerge_; | 
 |  | 
 |     std::unordered_set<core::ir::Block*> current_blocks_; | 
 |  | 
 |     // For each block, we keep a set of SPIR-V `id`s which are known in that scope. | 
 |     std::vector<std::unordered_set<uint32_t>> id_stack_; | 
 |  | 
 |     // If we're in a switch, is populated with the IDs of the blocks for each of the switch | 
 |     // selectors. This lets us watch for fallthrough when emitting branch instructions. | 
 |     std::vector<std::unordered_set<uint32_t>> current_switch_blocks_; | 
 |  | 
 |     /// Maps from a spirv-v block id to the corresponding block in the IR | 
 |     std::unordered_map<uint32_t, core::ir::Block*> spirv_id_to_block_; | 
 |  | 
 |     // Map of continue block id to the phi types which need to be returned by | 
 |     // the continue target | 
 |     std::unordered_map<uint32_t, std::vector<uint32_t>> continue_blk_phis_; | 
 |  | 
 |     // A stack of values which need to be replaced as we finish processing a | 
 |     // block. Used to store `phi` information so we can retrieve values which | 
 |     // are defined after the `OpPhi` instruction. | 
 |     std::vector<std::vector<ReplacementValue>> values_to_replace_; | 
 |  | 
 |     // A map of loop header to phi values returned by that loop header | 
 |     std::unordered_map<uint32_t, std::vector<uint32_t>> block_phi_values_; | 
 |  | 
 |     // Map of certain instructions back to their originating spirv block | 
 |     std::unordered_map<core::ir::Instruction*, uint32_t> inst_to_spirv_block_; | 
 |  | 
 |     // Structure hold spec composite information | 
 |     struct SpecComposite { | 
 |         // The composite type | 
 |         const core::type::Type* type; | 
 |         // The composite arguments | 
 |         Vector<uint32_t, 4> args; | 
 |     }; | 
 |  | 
 |     // The set of SPIR-V IDs which map to `OpSpecConstantComposite` information | 
 |     std::unordered_map<uint32_t, SpecComposite> spec_composites_; | 
 |  | 
 |     // Structures which are marked with `BufferBlock` and need to be reported as `Storage` address | 
 |     // space | 
 |     std::unordered_set<const core::type::Struct*> storage_buffer_types_; | 
 |  | 
 |     // Map of `var` to the access mode it was originally created with. This may be different from | 
 |     // the current mode if we needed to set a default mode. | 
 |     std::unordered_map<core::ir::Var*, core::Access> var_to_original_access_mode_; | 
 | }; | 
 |  | 
 | }  // namespace | 
 |  | 
 | Result<core::ir::Module> Parse(Slice<const uint32_t> spirv, const Options& options) { | 
 |     return Parser(options).Run(spirv); | 
 | } | 
 |  | 
 | }  // namespace tint::spirv::reader |