1 //===- LowerAtomic.cpp - Lower atomic intrinsics --------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This pass lowers atomic intrinsics to non-atomic form for use in a known
11 // non-preemptible environment.
13 //===----------------------------------------------------------------------===//
15 #include "llvm/Transforms/Scalar.h"
16 #include "llvm/IR/Function.h"
17 #include "llvm/IR/IRBuilder.h"
18 #include "llvm/IR/IntrinsicInst.h"
19 #include "llvm/Pass.h"
22 #define DEBUG_TYPE "loweratomic"
24 static bool LowerAtomicCmpXchgInst(AtomicCmpXchgInst *CXI) {
25 IRBuilder<> Builder(CXI->getParent(), CXI);
26 Value *Ptr = CXI->getPointerOperand();
27 Value *Cmp = CXI->getCompareOperand();
28 Value *Val = CXI->getNewValOperand();
30 LoadInst *Orig = Builder.CreateLoad(Ptr);
31 Value *Equal = Builder.CreateICmpEQ(Orig, Cmp);
32 Value *Res = Builder.CreateSelect(Equal, Val, Orig);
33 Builder.CreateStore(Res, Ptr);
35 CXI->replaceAllUsesWith(Orig);
36 CXI->eraseFromParent();
40 static bool LowerAtomicRMWInst(AtomicRMWInst *RMWI) {
41 IRBuilder<> Builder(RMWI->getParent(), RMWI);
42 Value *Ptr = RMWI->getPointerOperand();
43 Value *Val = RMWI->getValOperand();
45 LoadInst *Orig = Builder.CreateLoad(Ptr);
48 switch (RMWI->getOperation()) {
49 default: llvm_unreachable("Unexpected RMW operation");
50 case AtomicRMWInst::Xchg:
53 case AtomicRMWInst::Add:
54 Res = Builder.CreateAdd(Orig, Val);
56 case AtomicRMWInst::Sub:
57 Res = Builder.CreateSub(Orig, Val);
59 case AtomicRMWInst::And:
60 Res = Builder.CreateAnd(Orig, Val);
62 case AtomicRMWInst::Nand:
63 Res = Builder.CreateNot(Builder.CreateAnd(Orig, Val));
65 case AtomicRMWInst::Or:
66 Res = Builder.CreateOr(Orig, Val);
68 case AtomicRMWInst::Xor:
69 Res = Builder.CreateXor(Orig, Val);
71 case AtomicRMWInst::Max:
72 Res = Builder.CreateSelect(Builder.CreateICmpSLT(Orig, Val),
75 case AtomicRMWInst::Min:
76 Res = Builder.CreateSelect(Builder.CreateICmpSLT(Orig, Val),
79 case AtomicRMWInst::UMax:
80 Res = Builder.CreateSelect(Builder.CreateICmpULT(Orig, Val),
83 case AtomicRMWInst::UMin:
84 Res = Builder.CreateSelect(Builder.CreateICmpULT(Orig, Val),
88 Builder.CreateStore(Res, Ptr);
89 RMWI->replaceAllUsesWith(Orig);
90 RMWI->eraseFromParent();
94 static bool LowerFenceInst(FenceInst *FI) {
95 FI->eraseFromParent();
99 static bool LowerLoadInst(LoadInst *LI) {
100 LI->setAtomic(NotAtomic);
104 static bool LowerStoreInst(StoreInst *SI) {
105 SI->setAtomic(NotAtomic);
110 struct LowerAtomic : public BasicBlockPass {
112 LowerAtomic() : BasicBlockPass(ID) {
113 initializeLowerAtomicPass(*PassRegistry::getPassRegistry());
115 bool runOnBasicBlock(BasicBlock &BB) override {
116 if (skipOptnoneFunction(BB))
118 bool Changed = false;
119 for (BasicBlock::iterator DI = BB.begin(), DE = BB.end(); DI != DE; ) {
120 Instruction *Inst = DI++;
121 if (FenceInst *FI = dyn_cast<FenceInst>(Inst))
122 Changed |= LowerFenceInst(FI);
123 else if (AtomicCmpXchgInst *CXI = dyn_cast<AtomicCmpXchgInst>(Inst))
124 Changed |= LowerAtomicCmpXchgInst(CXI);
125 else if (AtomicRMWInst *RMWI = dyn_cast<AtomicRMWInst>(Inst))
126 Changed |= LowerAtomicRMWInst(RMWI);
127 else if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
130 } else if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
140 char LowerAtomic::ID = 0;
141 INITIALIZE_PASS(LowerAtomic, "loweratomic",
142 "Lower atomic intrinsics to non-atomic form",
145 Pass *llvm::createLowerAtomicPass() { return new LowerAtomic(); }