| // 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 |
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| // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| |
| #include "src/tint/lang/core/ir/transform/value_to_let.h" |
| |
| #include "src/tint/lang/core/ir/builder.h" |
| #include "src/tint/lang/core/ir/validator.h" |
| |
| using namespace tint::core::fluent_types; // NOLINT |
| using namespace tint::core::number_suffixes; // NOLINT |
| |
| namespace tint::core::ir::transform { |
| |
| namespace { |
| |
| /// Access is an enumerator of memory access operations |
| enum class Access : uint8_t { kLoad, kStore }; |
| /// Accesses is a set of of Access |
| using Accesses = EnumSet<Access>; |
| |
| /// @returns the accesses that may be performed by the instruction @p inst |
| Accesses AccessesFor(ir::Instruction* inst) { |
| return tint::Switch<Accesses>( |
| inst, // |
| [&](const ir::Load*) { return Access::kLoad; }, // |
| [&](const ir::LoadVectorElement*) { return Access::kLoad; }, // |
| [&](const ir::Store*) { return Access::kStore; }, // |
| [&](const ir::StoreVectorElement*) { return Access::kStore; }, // |
| [&](const ir::Call*) { |
| return Accesses{Access::kLoad, Access::kStore}; |
| }, |
| [&](Default) { return Accesses{}; }); |
| } |
| |
| /// PIMPL state for the transform. |
| struct State { |
| /// The IR module. |
| Module& ir; |
| |
| /// The IR builder. |
| Builder b{ir}; |
| |
| /// The type manager. |
| core::type::Manager& ty{ir.Types()}; |
| |
| /// Process the module. |
| void Process() { |
| // Process each block. |
| for (auto* block : ir.blocks.Objects()) { |
| Process(block); |
| } |
| } |
| |
| private: |
| void Process(ir::Block* block) { |
| // A set of possibly-inlinable values returned by a instructions that has not yet been |
| // marked-for or ruled-out-for inlining. |
| Hashset<ir::InstructionResult*, 32> pending_resolution; |
| // The accesses of the values in pending_resolution. |
| Access pending_access = Access::kLoad; |
| |
| auto put_pending_in_lets = [&] { |
| for (auto& pending : pending_resolution) { |
| PutInLet(pending); |
| } |
| pending_resolution.Clear(); |
| }; |
| |
| auto maybe_put_in_let = [&](auto* inst) { |
| if (auto* result = inst->Result(0)) { |
| auto& usages = result->Usages(); |
| switch (usages.Count()) { |
| case 0: // No usage |
| break; |
| case 1: { // Single usage |
| auto usage = (*usages.begin())->instruction; |
| if (usage->Block() == inst->Block()) { |
| // Usage in same block. Assign to pending_resolution, as we don't |
| // know whether its safe to inline yet. |
| pending_resolution.Add(result); |
| } else { |
| // Usage from another block. Cannot inline. |
| inst = PutInLet(result); |
| } |
| break; |
| } |
| default: // Value has multiple usages. Cannot inline. |
| inst = PutInLet(result); |
| break; |
| } |
| } |
| }; |
| |
| for (ir::Instruction* inst = block->Front(); inst; inst = inst->next) { |
| // This transform assumes that all multi-result instructions have been replaced |
| TINT_ASSERT(inst->Results().Length() < 2); |
| |
| // The memory accesses of this instruction |
| auto accesses = AccessesFor(inst); |
| |
| for (auto* operand : inst->Operands()) { |
| // If the operand is in pending_resolution, then we know it has a single use and |
| // because it hasn't been removed with put_pending_in_lets(), we know its safe to |
| // inline without breaking access ordering. By inlining the operand, we are pulling |
| // the operand's instruction into the same statement as this instruction, so this |
| // instruction adopts the access of the operand. |
| if (auto* result = As<InstructionResult>(operand)) { |
| if (pending_resolution.Remove(result)) { |
| // Var and Let are always statements, and so can never be inlined. As such, |
| // they do not need to propagate the pending resolution through them. |
| if (!inst->IsAnyOf<Var, Let>()) { |
| accesses.Add(pending_access); |
| } |
| } |
| } |
| } |
| |
| if (accesses.Contains(Access::kStore)) { // Note: Also handles load + store |
| put_pending_in_lets(); |
| maybe_put_in_let(inst); |
| } else if (accesses.Contains(Access::kLoad)) { |
| if (pending_access != Access::kLoad) { |
| put_pending_in_lets(); |
| pending_access = Access::kLoad; |
| } |
| maybe_put_in_let(inst); |
| } |
| } |
| } |
| |
| /// PutInLet places the value into a new 'let' instruction, immediately after the value's |
| /// instruction |
| /// @param value the value to place into the 'let' |
| /// @return the created 'let' instruction. |
| ir::Let* PutInLet(ir::InstructionResult* value) { |
| auto* inst = value->Instruction(); |
| auto* let = b.Let(value->Type()); |
| value->ReplaceAllUsesWith(let->Result(0)); |
| let->SetValue(value); |
| let->InsertAfter(inst); |
| if (auto name = b.ir.NameOf(value); name.IsValid()) { |
| b.ir.SetName(let->Result(0), name); |
| b.ir.ClearName(value); |
| } |
| return let; |
| } |
| }; |
| |
| } // namespace |
| |
| Result<SuccessType> ValueToLet(Module& ir) { |
| auto result = ValidateAndDumpIfNeeded(ir, "ValueToLet transform"); |
| if (result != Success) { |
| return result; |
| } |
| |
| State{ir}.Process(); |
| |
| return Success; |
| } |
| |
| } // namespace tint::core::ir::transform |