aboutsummaryrefslogtreecommitdiffstats
path: root/contrib/libs/llvm14/lib/Transforms/Scalar/LowerAtomic.cpp
blob: 4063e4fe04726a36ee6441ca4b34b2983b66135d (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
//===- 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/LowerAtomic.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/Transforms/Scalar.h"
using namespace llvm;

#define DEBUG_TYPE "loweratomic"

static bool LowerAtomicCmpXchgInst(AtomicCmpXchgInst *CXI) {
  IRBuilder<> Builder(CXI);
  Value *Ptr = CXI->getPointerOperand();
  Value *Cmp = CXI->getCompareOperand();
  Value *Val = CXI->getNewValOperand();

  LoadInst *Orig = Builder.CreateLoad(Val->getType(), Ptr);
  Value *Equal = Builder.CreateICmpEQ(Orig, Cmp);
  Value *Res = Builder.CreateSelect(Equal, Val, Orig);
  Builder.CreateStore(Res, Ptr);

  Res = Builder.CreateInsertValue(UndefValue::get(CXI->getType()), Orig, 0);
  Res = Builder.CreateInsertValue(Res, Equal, 1);

  CXI->replaceAllUsesWith(Res);
  CXI->eraseFromParent();
  return true;
}

bool llvm::lowerAtomicRMWInst(AtomicRMWInst *RMWI) {
  IRBuilder<> Builder(RMWI);
  Value *Ptr = RMWI->getPointerOperand();
  Value *Val = RMWI->getValOperand();

  LoadInst *Orig = Builder.CreateLoad(Val->getType(), Ptr);
  Value *Res = nullptr;

  switch (RMWI->getOperation()) {
  default: llvm_unreachable("Unexpected RMW operation");
  case AtomicRMWInst::Xchg:
    Res = Val;
    break;
  case AtomicRMWInst::Add:
    Res = Builder.CreateAdd(Orig, Val);
    break;
  case AtomicRMWInst::Sub:
    Res = Builder.CreateSub(Orig, Val);
    break;
  case AtomicRMWInst::And:
    Res = Builder.CreateAnd(Orig, Val);
    break;
  case AtomicRMWInst::Nand:
    Res = Builder.CreateNot(Builder.CreateAnd(Orig, Val));
    break;
  case AtomicRMWInst::Or:
    Res = Builder.CreateOr(Orig, Val);
    break;
  case AtomicRMWInst::Xor:
    Res = Builder.CreateXor(Orig, Val);
    break;
  case AtomicRMWInst::Max:
    Res = Builder.CreateSelect(Builder.CreateICmpSLT(Orig, Val),
                               Val, Orig);
    break;
  case AtomicRMWInst::Min:
    Res = Builder.CreateSelect(Builder.CreateICmpSLT(Orig, Val),
                               Orig, Val);
    break;
  case AtomicRMWInst::UMax:
    Res = Builder.CreateSelect(Builder.CreateICmpULT(Orig, Val),
                               Val, Orig);
    break;
  case AtomicRMWInst::UMin:
    Res = Builder.CreateSelect(Builder.CreateICmpULT(Orig, Val),
                               Orig, Val);
    break;
  case AtomicRMWInst::FAdd:
    Res = Builder.CreateFAdd(Orig, Val);
    break;
  case AtomicRMWInst::FSub:
    Res = Builder.CreateFSub(Orig, Val);
    break;
  }
  Builder.CreateStore(Res, Ptr);
  RMWI->replaceAllUsesWith(Orig);
  RMWI->eraseFromParent();
  return true;
}

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(); }