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Merge pull request #236 from hvdijk/manual-type-legalization
Manual type legalization.
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38 changes: 38 additions & 0 deletions
38
modules/compiler/test/lit/passes/manual_type_legalization.ll
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|---|---|---|
| @@ -0,0 +1,38 @@ | ||
| ; Copyright (C) Codeplay Software Limited | ||
| ; | ||
| ; Licensed under the Apache License, Version 2.0 (the "License") with LLVM | ||
| ; Exceptions; you may not use this file except in compliance with the License. | ||
| ; You may obtain a copy of the License at | ||
| ; | ||
| ; https://github.com/codeplaysoftware/oneapi-construction-kit/blob/main/LICENSE.txt | ||
| ; | ||
| ; Unless required by applicable law or agreed to in writing, software | ||
| ; distributed under the License is distributed on an "AS IS" BASIS, WITHOUT | ||
| ; WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the | ||
| ; License for the specific language governing permissions and limitations | ||
| ; under the License. | ||
| ; | ||
| ; SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception | ||
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| ; RUN: muxc --passes manual-type-legalization,verify -S %s | FileCheck %s | ||
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| ; Make sure we use a triple that does not have half as a legal type. | ||
| target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128" | ||
| target triple = "spir64-unknown-unknown" | ||
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| ; CHECK-LABEL: define half @f | ||
| ; CHECK-DAG: [[AEXT:%.*]] = fpext half %a to float | ||
| ; CHECK-DAG: [[BEXT:%.*]] = fpext half %b to float | ||
| ; CHECK-DAG: [[CEXT:%.*]] = fpext half %c to float | ||
| ; CHECK-DAG: [[DADD:%.*]] = fadd float [[AEXT]], [[BEXT]] | ||
| ; CHECK-DAG: [[DTRUNC:%.*]] = fptrunc float [[DADD]] to half | ||
| ; CHECK-DAG: [[DEXT:%.*]] = fpext half [[DTRUNC]] to float | ||
| ; CHECK-DAG: [[EADD:%.*]] = fadd float [[DEXT]], [[CEXT]] | ||
| ; CHECK-DAG: [[ETRUNC:%.*]] = fptrunc float [[EADD]] to half | ||
| ; CHECK: ret half [[ETRUNC]] | ||
| define half @f(half %a, half %b, half %c) { | ||
| entry: | ||
| %d = fadd half %a, %b | ||
| %e = fadd half %d, %c | ||
| ret half %e | ||
| } |
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56 changes: 56 additions & 0 deletions
56
modules/compiler/utils/include/compiler/utils/manual_type_legalization_pass.h
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| // Copyright (C) Codeplay Software Limited | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License") with LLVM | ||
| // Exceptions; you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // https://github.com/codeplaysoftware/oneapi-construction-kit/blob/main/LICENSE.txt | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, WITHOUT | ||
| // WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the | ||
| // License for the specific language governing permissions and limitations | ||
| // under the License. | ||
| // | ||
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception | ||
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| #ifndef COMPILER_UTILS_MANUAL_TYPE_LEGALIZATION_PASS_H_INCLUDED | ||
| #define COMPILER_UTILS_MANUAL_TYPE_LEGALIZATION_PASS_H_INCLUDED | ||
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| #include <llvm/IR/PassManager.h> | ||
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| namespace compiler { | ||
| namespace utils { | ||
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| /// Manual type legalization pass. | ||
| /// | ||
| /// On targets that do not natively support \c half, promote operations on \c | ||
| /// half to \c float instead. | ||
| /// | ||
| /// When LLVM encounters floating point operations in a type it does not support | ||
| /// natively, it extends its operands to an extended precision floating point | ||
| /// type, performs the operation in that extended type, and rounds the result | ||
| /// back to the original type. However, when it extends its operands to an | ||
| /// extended precision floating point type, if an operand itself was a floating | ||
| /// point operation that was also so extended, its rounding and re-extension are | ||
| /// skipped. This causes issues for code that relies on exact rounding of | ||
| /// intermediate results, which we avoid by manually doing this promition | ||
| /// ourselves. | ||
| /// | ||
| /// Simply performing operations in a wider floating point type and rounding | ||
| /// back to the narrow floating point type is not, in general, correct, due to | ||
| /// double rounding. For addition, subtraction, and multiplications, \c float | ||
| /// provides enough additional precision that double rounding is known not to be | ||
| /// an issue. For other operations, this pass may generate incorrect results, | ||
| /// but this should only happen in cases where letting the operation pass | ||
| /// through to LLVM would result in the same incorrect results. | ||
| struct ManualTypeLegalizationPass final | ||
| : llvm::PassInfoMixin<ManualTypeLegalizationPass> { | ||
| llvm::PreservedAnalyses run(llvm::Function &F, | ||
| llvm::FunctionAnalysisManager &FAM); | ||
| }; | ||
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| } // namespace utils | ||
| } // namespace compiler | ||
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| #endif // COMPILER_UTILS_MANUAL_TYPE_LEGALIZATION_PASS_H_INCLUDED |
129 changes: 129 additions & 0 deletions
129
modules/compiler/utils/source/manual_type_legalization_pass.cpp
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| // Copyright (C) Codeplay Software Limited | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License") with LLVM | ||
| // Exceptions; you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // https://github.com/codeplaysoftware/oneapi-construction-kit/blob/main/LICENSE.txt | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, WITHOUT | ||
| // WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the | ||
| // License for the specific language governing permissions and limitations | ||
| // under the License. | ||
| // | ||
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception | ||
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| #include <compiler/utils/manual_type_legalization_pass.h> | ||
| #include <llvm/ADT/DenseMap.h> | ||
| #include <llvm/Analysis/TargetTransformInfo.h> | ||
| #include <llvm/IR/IRBuilder.h> | ||
| #include <llvm/IR/InstrTypes.h> | ||
| #include <llvm/IR/Instructions.h> | ||
| #include <llvm/IR/Module.h> | ||
| #include <llvm/IR/PassManager.h> | ||
| #include <llvm/IR/Type.h> | ||
| #include <llvm/Support/Casting.h> | ||
| #include <llvm/TargetParser/Triple.h> | ||
| #include <multi_llvm/llvm_version.h> | ||
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| using namespace llvm; | ||
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| PreservedAnalyses compiler::utils::ManualTypeLegalizationPass::run( | ||
| Function &F, FunctionAnalysisManager &FAM) { | ||
| auto &TTI = FAM.getResult<TargetIRAnalysis>(F); | ||
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| auto *HalfT = Type::getHalfTy(F.getContext()); | ||
| auto *FloatT = Type::getFloatTy(F.getContext()); | ||
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| // Targets where half is a legal type do not need this pass. Targets where | ||
| // half is promoted using "soft promotion" rules also do not need this pass. | ||
| // We cannot reliably determine which targets these are, but that is okay, on | ||
| // targets where this pass is not needed it does no harm, it merely wastes | ||
| // time. | ||
| llvm::Triple TT(F.getParent()->getTargetTriple()); | ||
| if (TTI.isTypeLegal(HalfT) || TT.isX86() || TT.isRISCV()) { | ||
| return PreservedAnalyses::all(); | ||
| } | ||
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| DenseMap<Value *, Value *> FPExtVals; | ||
| IRBuilder<> B(F.getContext()); | ||
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| auto CreateFPExt = [&](Value *V, Type *ExtTy) { | ||
| auto *&FPExt = FPExtVals[V]; | ||
| if (!FPExt) { | ||
| if (auto *I = dyn_cast<Instruction>(V)) { | ||
| #if LLVM_VERSION_GREATER_EQUAL(18, 0) | ||
| std::optional<BasicBlock::iterator> IPAD; | ||
| IPAD = I->getInsertionPointAfterDef(); | ||
| #else | ||
| std::optional<Instruction *> IPAD; | ||
| if (auto *IPADRaw = I->getInsertionPointAfterDef()) { | ||
| IPAD = IPADRaw; | ||
| } | ||
| #endif | ||
| assert(IPAD && | ||
| "getInsertionPointAfterDef() should return an insertion point " | ||
| "for all FP16 instructions"); | ||
| B.SetInsertPoint(*IPAD); | ||
| } else { | ||
| B.SetInsertPointPastAllocas(&F); | ||
| } | ||
| FPExt = B.CreateFPExt(V, ExtTy, V->getName() + ".fpext"); | ||
| } | ||
| return FPExt; | ||
| }; | ||
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| bool Changed = false; | ||
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| for (auto &BB : F) { | ||
| for (auto &I : make_early_inc_range(BB)) { | ||
| auto *BO = dyn_cast<BinaryOperator>(&I); | ||
| if (!BO) continue; | ||
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| auto *T = BO->getType(); | ||
| auto *VecT = dyn_cast<VectorType>(T); | ||
| auto *ElT = VecT ? VecT->getElementType() : T; | ||
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| if (ElT != HalfT) continue; | ||
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| auto *LHS = BO->getOperand(0); | ||
| auto *RHS = BO->getOperand(1); | ||
| assert(LHS->getType() == T && | ||
| "Expected matching types for floating point operation"); | ||
| assert(RHS->getType() == T && | ||
| "Expected matching types for floating point operation"); | ||
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| auto *ExtElT = FloatT; | ||
| auto *ExtT = | ||
| VecT ? VectorType::get(ExtElT, VecT->getElementCount()) : ExtElT; | ||
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| auto *LHSExt = CreateFPExt(LHS, ExtT); | ||
| auto *RHSExt = CreateFPExt(RHS, ExtT); | ||
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| B.SetInsertPoint(BO); | ||
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| B.setFastMathFlags(BO->getFastMathFlags()); | ||
| auto *OpExt = B.CreateBinOp(BO->getOpcode(), LHSExt, RHSExt, | ||
| BO->getName() + ".fpext"); | ||
| B.clearFastMathFlags(); | ||
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| auto *Trunc = B.CreateFPTrunc(OpExt, T); | ||
| Trunc->takeName(BO); | ||
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| BO->replaceAllUsesWith(Trunc); | ||
| BO->eraseFromParent(); | ||
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| Changed = true; | ||
| } | ||
| } | ||
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| PreservedAnalyses PA; | ||
| if (Changed) { | ||
| PA = PreservedAnalyses::none(); | ||
| PA.preserveSet<CFGAnalyses>(); | ||
| } else { | ||
| PA = PreservedAnalyses::all(); | ||
| } | ||
| return PA; | ||
| } |
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