// Copyright 2023 The Dawn & Tint Authors
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#include "src/tint/lang/spirv/reader/parser/parser.h"

#include <algorithm>
#include <memory>
#include <utility>
#include <vector>

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);
#include "source/opt/build_module.h"
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/spirv/validate/validate.h"

using namespace tint::core::fluent_types;  // NOLINT

namespace tint::spirv::reader {

namespace {

/// 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:
    /// @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");
        }

        // 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") {
                return Failure("SPIR-V extension '" + name + "' is not supported");
            }
        }

        {
            TINT_SCOPED_ASSIGNMENT(current_block_, ir_.root_block);
            EmitModuleScopeVariables();
        }

        EmitFunctions();

        EmitEntryPoints();

        // TODO(crbug.com/tint/1907): Handle annotation instructions.
        // TODO(crbug.com/tint/1907): Handle names.

        return std::move(ir_);
    }

    /// @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;
            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;
            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) {
        return types_.GetOrAdd(TypeKey{type, access_mode}, [&]() -> const core::type::Type* {
            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());
                case spvtools::opt::analysis::Type::kStruct:
                    return EmitStruct(type->AsStruct());
                case spvtools::opt::analysis::Type::kPointer: {
                    auto* ptr_ty = type->AsPointer();
                    return ty_.ptr(AddressSpace(ptr_ty->storage_class()),
                                   Type(ptr_ty->pointee_type()), access_mode);
                }
                default:
                    TINT_UNIMPLEMENTED() << "unhandled SPIR-V type: " << type->str();
            }
        });
    }

    /// @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) {
        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);

        // TODO(crbug.com/1907): Handle decorations that affect the array layout.

        return ty_.array(Type(arr_ty->element_type()), static_cast<uint32_t>(count_val));
    }

    /// @param struct_ty a SPIR-V struct object
    /// @returns a Tint struct object
    const core::type::Type* EmitStruct(const spvtools::opt::analysis::Struct* struct_ty) {
        if (struct_ty->NumberOfComponents() == 0) {
            TINT_ICE() << "empty structures are not supported";
        }

        // 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::kCenter};
                }
                return attributes.interpolation.value();
            };

            // 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::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];
                    }
                }
            }

            // TODO(crbug.com/tint/1907): Use OpMemberName to name it.
            members.Push(ty_.Get<core::type::StructMember>(ir_.symbols.New(), member_ty, i, offset,
                                                           align, member_ty->Size(),
                                                           std::move(attributes)));

            current_size = offset + member_ty->Size();
        }
        // TODO(crbug.com/tint/1907): Use OpName to name it.
        return ty_.Struct(ir_.symbols.New(), std::move(members));
    }

    /// @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_()); });
    }

    /// @param id a SPIR-V result ID
    /// @returns a Tint value object
    core::ir::Value* Value(uint32_t id) {
        return values_.GetOrAdd(id, [&]() -> core::ir::Value* {
            if (auto* c = spirv_context_->get_constant_mgr()->FindDeclaredConstant(id)) {
                return b_.Constant(Constant(c));
            }
            TINT_UNREACHABLE() << "missing value for result ID " << id;
        });
    }

    /// @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) { values_.Add(result_id, value); }

    /// Emit an instruction to the current block.
    /// @param inst the instruction to emit
    /// @param result_id an optional SPIR-V result ID to register the instruction result for
    void Emit(core::ir::Instruction* inst, uint32_t result_id = 0) {
        current_block_->Append(inst);
        if (result_id != 0) {
            TINT_ASSERT(inst->Results().Length() == 1u);
            AddValue(result_id, inst->Result(0));
        }
    }

    /// Emit the module-scope variables.
    void EmitModuleScopeVariables() {
        for (auto& inst : spirv_context_->module()->types_values()) {
            if (inst.opcode() == spv::Op::OpVariable) {
                EmitVar(inst);
            }
        }
    }

    /// Emit the functions.
    void EmitFunctions() {
        for (auto& func : *spirv_context_->module()) {
            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);
                params.Push(param);
            });

            current_function_ = Function(func.result_id());
            current_function_->SetParams(std::move(params));
            current_function_->SetReturnType(Type(func.type_id()));

            functions_.Add(func.result_id(), current_function_);
            EmitBlock(current_function_->Block(), *func.entry());
        }
    }

    /// Emit entry point attributes.
    void EmitEntryPoints() {
        // 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());
        }

        // 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;
            }
        }
    }

    /// 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, const spvtools::opt::BasicBlock& src) {
        TINT_SCOPED_ASSIGNMENT(current_block_, dst);
        for (auto& inst : src) {
            switch (inst.opcode()) {
                case spv::Op::OpAccessChain:
                case spv::Op::OpInBoundsAccessChain:
                    EmitAccess(inst);
                    break;
                case spv::Op::OpCompositeConstruct:
                    EmitConstruct(inst);
                    break;
                case spv::Op::OpCompositeExtract:
                    EmitCompositeExtract(inst);
                    break;
                case spv::Op::OpFAdd:
                    EmitBinary(inst, core::BinaryOp::kAdd);
                    break;
                case spv::Op::OpFMul:
                    EmitBinary(inst, core::BinaryOp::kMultiply);
                    break;
                case spv::Op::OpFunctionCall:
                    EmitFunctionCall(inst);
                    break;
                case spv::Op::OpIAdd:
                    EmitBinary(inst, core::BinaryOp::kAdd);
                    break;
                case spv::Op::OpLoad:
                    Emit(b_.Load(Value(inst.GetSingleWordOperand(2))), inst.result_id());
                    break;
                case spv::Op::OpReturn:
                    Emit(b_.Return(current_function_));
                    break;
                case spv::Op::OpReturnValue:
                    Emit(b_.Return(current_function_, Value(inst.GetSingleWordOperand(0))));
                    break;
                case spv::Op::OpStore:
                    Emit(b_.Store(Value(inst.GetSingleWordOperand(0)),
                                  Value(inst.GetSingleWordOperand(1))));
                    break;
                case spv::Op::OpVariable:
                    EmitVar(inst);
                    break;
                default:
                    TINT_UNIMPLEMENTED()
                        << "unhandled SPIR-V instruction: " << static_cast<uint32_t>(inst.opcode());
            }
        }
    }

    /// @param inst the SPIR-V instruction for OpAccessChain
    void EmitAccess(const spvtools::opt::Instruction& inst) {
        Vector<core::ir::Value*, 4> indices;
        for (uint32_t i = 3; i < inst.NumOperandWords(); i++) {
            indices.Push(Value(inst.GetSingleWordOperand(i)));
        }
        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 binary operator to use
    void EmitBinary(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);
        Emit(binary, 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 OpCompositeConstruct
    void EmitConstruct(const spvtools::opt::Instruction& inst) {
        Vector<core::ir::Value*, 4> values;
        for (uint32_t i = 2; i < inst.NumOperandWords(); i++) {
            values.Push(Value(inst.GetSingleWordOperand(i)));
        }
        auto* construct = b_.Construct(Type(inst.type_id()), std::move(values));
        Emit(construct, inst.result_id());
    }

    /// @param inst the SPIR-V instruction for OpFunctionCall
    void EmitFunctionCall(const spvtools::opt::Instruction& inst) {
        // TODO(crbug.com/tint/1907): Capture result.
        Vector<core::ir::Value*, 4> args;
        for (uint32_t i = 3; i < inst.NumOperandWords(); i++) {
            args.Push(Value(inst.GetSingleWordOperand(i)));
        }
        Emit(b_.Call(Function(inst.GetSingleWordInOperand(0)), std::move(args)), 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{
                    core::InterpolationType::kPerspective, core::InterpolationSampling::kCenter};
            }
            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::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;
                default:
                    TINT_UNIMPLEMENTED() << "unhandled decoration " << d;
            }
        }

        auto* var = b_.Var(Type(inst.type_id(), access_mode)->As<core::type::Pointer>());
        if (inst.NumOperands() > 3) {
            var->SetInitializer(Value(inst.GetSingleWordOperand(3)));
        }

        if (group || binding) {
            TINT_ASSERT(group && binding);
            var->SetBindingPoint(group.value(), binding.value());
        }
        var->SetAttributes(std::move(io_attributes));

        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 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_;

    /// The SPIR-V context containing the SPIR-V tools intermediate representation.
    std::unique_ptr<spvtools::opt::IRContext> spirv_context_;
};

}  // namespace

Result<core::ir::Module> Parse(Slice<const uint32_t> spirv) {
    return Parser{}.Run(spirv);
}

}  // namespace tint::spirv::reader