| 1 | //===- LowerAtomic.cpp - Lower atomic intrinsics --------------------------===// |
|---|---|
| 2 | // |
| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| 4 | // See https://llvm.org/LICENSE.txt for license information. |
| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| 6 | // |
| 7 | //===----------------------------------------------------------------------===// |
| 8 | // |
| 9 | // This pass lowers atomic intrinsics to non-atomic form for use in a known |
| 10 | // non-preemptible environment. |
| 11 | // |
| 12 | //===----------------------------------------------------------------------===// |
| 13 | |
| 14 | #include "llvm/Transforms/Scalar/LowerAtomicPass.h" |
| 15 | #include "llvm/IR/Function.h" |
| 16 | #include "llvm/IR/IRBuilder.h" |
| 17 | #include "llvm/InitializePasses.h" |
| 18 | #include "llvm/Pass.h" |
| 19 | #include "llvm/Transforms/Scalar.h" |
| 20 | #include "llvm/Transforms/Utils/LowerAtomic.h" |
| 21 | using namespace llvm; |
| 22 | |
| 23 | #define DEBUG_TYPE "lower-atomic" |
| 24 | |
| 25 | static bool LowerFenceInst(FenceInst *FI) { |
| 26 | FI->eraseFromParent(); |
| 27 | return true; |
| 28 | } |
| 29 | |
| 30 | static bool LowerLoadInst(LoadInst *LI) { |
| 31 | LI->setAtomic(Ordering: AtomicOrdering::NotAtomic); |
| 32 | return true; |
| 33 | } |
| 34 | |
| 35 | static bool LowerStoreInst(StoreInst *SI) { |
| 36 | SI->setAtomic(Ordering: AtomicOrdering::NotAtomic); |
| 37 | return true; |
| 38 | } |
| 39 | |
| 40 | static bool runOnBasicBlock(BasicBlock &BB) { |
| 41 | bool Changed = false; |
| 42 | for (Instruction &Inst : make_early_inc_range(Range&: BB)) { |
| 43 | if (FenceInst *FI = dyn_cast<FenceInst>(Val: &Inst)) |
| 44 | Changed |= LowerFenceInst(FI); |
| 45 | else if (AtomicCmpXchgInst *CXI = dyn_cast<AtomicCmpXchgInst>(Val: &Inst)) |
| 46 | Changed |= lowerAtomicCmpXchgInst(CXI); |
| 47 | else if (AtomicRMWInst *RMWI = dyn_cast<AtomicRMWInst>(Val: &Inst)) |
| 48 | Changed |= lowerAtomicRMWInst(RMWI); |
| 49 | else if (LoadInst *LI = dyn_cast<LoadInst>(Val: &Inst)) { |
| 50 | if (LI->isAtomic()) |
| 51 | LowerLoadInst(LI); |
| 52 | } else if (StoreInst *SI = dyn_cast<StoreInst>(Val: &Inst)) { |
| 53 | if (SI->isAtomic()) |
| 54 | LowerStoreInst(SI); |
| 55 | } |
| 56 | } |
| 57 | return Changed; |
| 58 | } |
| 59 | |
| 60 | static bool lowerAtomics(Function &F) { |
| 61 | bool Changed = false; |
| 62 | for (BasicBlock &BB : F) { |
| 63 | Changed |= runOnBasicBlock(BB); |
| 64 | } |
| 65 | return Changed; |
| 66 | } |
| 67 | |
| 68 | PreservedAnalyses LowerAtomicPass::run(Function &F, FunctionAnalysisManager &) { |
| 69 | if (lowerAtomics(F)) |
| 70 | return PreservedAnalyses::none(); |
| 71 | return PreservedAnalyses::all(); |
| 72 | } |
| 73 | |
| 74 | namespace { |
| 75 | class LowerAtomicLegacyPass : public FunctionPass { |
| 76 | public: |
| 77 | static char ID; |
| 78 | |
| 79 | LowerAtomicLegacyPass() : FunctionPass(ID) { |
| 80 | initializeLowerAtomicLegacyPassPass(*PassRegistry::getPassRegistry()); |
| 81 | } |
| 82 | |
| 83 | bool runOnFunction(Function &F) override { |
| 84 | // Don't skip optnone functions; atomics still need to be lowered. |
| 85 | FunctionAnalysisManager DummyFAM; |
| 86 | auto PA = Impl.run(F, DummyFAM); |
| 87 | return !PA.areAllPreserved(); |
| 88 | } |
| 89 | |
| 90 | private: |
| 91 | LowerAtomicPass Impl; |
| 92 | }; |
| 93 | } |
| 94 | |
| 95 | char LowerAtomicLegacyPass::ID = 0; |
| 96 | INITIALIZE_PASS(LowerAtomicLegacyPass, "loweratomic", |
| 97 | "Lower atomic intrinsics to non-atomic form", false, false) |
| 98 | |
| 99 | Pass *llvm::createLowerAtomicPass() { return new LowerAtomicLegacyPass(); } |
| 100 |