llvm/lib/Transforms/Utils/LowerAtomic.cpp

   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/Utils/LowerAtomic.h"
  15 #include "llvm/IR/Function.h"
  16 #include "llvm/IR/IRBuilder.h"
  17 #include "llvm/InitializePasses.h"
  18 #include "llvm/Pass.h"
  19 using namespace llvm;
  20
  21 #define DEBUG_TYPE "loweratomic"
  22
  23 bool llvm::lowerAtomicCmpXchgInst(AtomicCmpXchgInst *CXI) {
  24   IRBuilder<> Builder(CXI);
  25   Value *Ptr = CXI->getPointerOperand();
  26   Value *Cmp = CXI->getCompareOperand();
  27   Value *Val = CXI->getNewValOperand();
  28
  29   LoadInst *Orig = Builder.CreateLoad(Val->getType(), Ptr);
  30   Value *Equal = Builder.CreateICmpEQ(Orig, Cmp);
  31   Value *Res = Builder.CreateSelect(Equal, Val, Orig);
  32   Builder.CreateStore(Res, Ptr);
  33
  34   Res = Builder.CreateInsertValue(PoisonValue::get(CXI->getType()), Orig, 0);
  35   Res = Builder.CreateInsertValue(Res, Equal, 1);
  36
  37   CXI->replaceAllUsesWith(Res);
  38   CXI->eraseFromParent();
  39   return true;
  40 }
  41
  42 Value *llvm::buildAtomicRMWValue(AtomicRMWInst::BinOp Op,
  43                                  IRBuilderBase &Builder, Value *Loaded,
  44                                  Value *Inc) {
  45   Value *NewVal;
  46   switch (Op) {
  47   case AtomicRMWInst::Xchg:
  48     return Inc;
  49   case AtomicRMWInst::Add:
  50     return Builder.CreateAdd(Loaded, Inc, "new");
  51   case AtomicRMWInst::Sub:
  52     return Builder.CreateSub(Loaded, Inc, "new");
  53   case AtomicRMWInst::And:
  54     return Builder.CreateAnd(Loaded, Inc, "new");
  55   case AtomicRMWInst::Nand:
  56     return Builder.CreateNot(Builder.CreateAnd(Loaded, Inc), "new");
  57   case AtomicRMWInst::Or:
  58     return Builder.CreateOr(Loaded, Inc, "new");
  59   case AtomicRMWInst::Xor:
  60     return Builder.CreateXor(Loaded, Inc, "new");
  61   case AtomicRMWInst::Max:
  62     NewVal = Builder.CreateICmpSGT(Loaded, Inc);
  63     return Builder.CreateSelect(NewVal, Loaded, Inc, "new");
  64   case AtomicRMWInst::Min:
  65     NewVal = Builder.CreateICmpSLE(Loaded, Inc);
  66     return Builder.CreateSelect(NewVal, Loaded, Inc, "new");
  67   case AtomicRMWInst::UMax:
  68     NewVal = Builder.CreateICmpUGT(Loaded, Inc);
  69     return Builder.CreateSelect(NewVal, Loaded, Inc, "new");
  70   case AtomicRMWInst::UMin:
  71     NewVal = Builder.CreateICmpULE(Loaded, Inc);
  72     return Builder.CreateSelect(NewVal, Loaded, Inc, "new");
  73   case AtomicRMWInst::FAdd:
  74     return Builder.CreateFAdd(Loaded, Inc, "new");
  75   case AtomicRMWInst::FSub:
  76     return Builder.CreateFSub(Loaded, Inc, "new");
  77   case AtomicRMWInst::FMax:
  78     return Builder.CreateMaxNum(Loaded, Inc);
  79   case AtomicRMWInst::FMin:
  80     return Builder.CreateMinNum(Loaded, Inc);
  81   default:
  82     llvm_unreachable("Unknown atomic op");
  83   }
  84 }
  85
  86 bool llvm::lowerAtomicRMWInst(AtomicRMWInst *RMWI) {
  87   IRBuilder<> Builder(RMWI);
  88   Value *Ptr = RMWI->getPointerOperand();
  89   Value *Val = RMWI->getValOperand();
  90
  91   LoadInst *Orig = Builder.CreateLoad(Val->getType(), Ptr);
  92   Value *Res = buildAtomicRMWValue(RMWI->getOperation(), Builder, Orig, Val);
  93   Builder.CreateStore(Res, Ptr);
  94   RMWI->replaceAllUsesWith(Orig);
  95   RMWI->eraseFromParent();
  96   return true;
  97 }