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//===- LowerAtomic.cpp - Lower atomic intrinsics --------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This pass lowers atomic intrinsics to non-atomic form for use in a known
// non-preemptible environment.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Scalar/LowerAtomicPass.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/LowerAtomic.h"
using namespace llvm;
#define DEBUG_TYPE "loweratomic"
static bool LowerFenceInst(FenceInst *FI) {
FI->eraseFromParent();
return true;
}
static bool LowerLoadInst(LoadInst *LI) {
LI->setAtomic(AtomicOrdering::NotAtomic);
return true;
}
static bool LowerStoreInst(StoreInst *SI) {
SI->setAtomic(AtomicOrdering::NotAtomic);
return true;
}
static bool runOnBasicBlock(BasicBlock &BB) {
bool Changed = false;
for (Instruction &Inst : make_early_inc_range(BB)) {
if (FenceInst *FI = dyn_cast<FenceInst>(&Inst))
Changed |= LowerFenceInst(FI);
else if (AtomicCmpXchgInst *CXI = dyn_cast<AtomicCmpXchgInst>(&Inst))
Changed |= lowerAtomicCmpXchgInst(CXI);
else if (AtomicRMWInst *RMWI = dyn_cast<AtomicRMWInst>(&Inst))
Changed |= lowerAtomicRMWInst(RMWI);
else if (LoadInst *LI = dyn_cast<LoadInst>(&Inst)) {
if (LI->isAtomic())
LowerLoadInst(LI);
} else if (StoreInst *SI = dyn_cast<StoreInst>(&Inst)) {
if (SI->isAtomic())
LowerStoreInst(SI);
}
}
return Changed;
}
static bool lowerAtomics(Function &F) {
bool Changed = false;
for (BasicBlock &BB : F) {
Changed |= runOnBasicBlock(BB);
}
return Changed;
}
PreservedAnalyses LowerAtomicPass::run(Function &F, FunctionAnalysisManager &) {
if (lowerAtomics(F))
return PreservedAnalyses::none();
return PreservedAnalyses::all();
}
namespace {
class LowerAtomicLegacyPass : public FunctionPass {
public:
static char ID;
LowerAtomicLegacyPass() : FunctionPass(ID) {
initializeLowerAtomicLegacyPassPass(*PassRegistry::getPassRegistry());
}
bool runOnFunction(Function &F) override {
// Don't skip optnone functions; atomics still need to be lowered.
FunctionAnalysisManager DummyFAM;
auto PA = Impl.run(F, DummyFAM);
return !PA.areAllPreserved();
}
private:
LowerAtomicPass Impl;
};
}
char LowerAtomicLegacyPass::ID = 0;
INITIALIZE_PASS(LowerAtomicLegacyPass, "loweratomic",
"Lower atomic intrinsics to non-atomic form", false, false)
Pass *llvm::createLowerAtomicPass() { return new LowerAtomicLegacyPass(); }
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