NVPTXAtomicLower.cpp

Go to the documentation of this file.

//===-- NVPTXAtomicLower.cpp - Lower atomics of local memory ----*- C++ -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
//  Lower atomics of local memory to simple load/stores
//
//===----------------------------------------------------------------------===//
 
#include "NVPTX.h"
#include "llvm/CodeGen/StackProtector.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/InstIterator.h"
#include "llvm/IR/Instructions.h"
#include "llvm/Transforms/Utils/LowerAtomic.h"
 
#include "MCTargetDesc/NVPTXBaseInfo.h"
using namespace llvm;
 
static bool lowerLocalMemoryAtomics(Function &F) {
  SmallVector<AtomicRMWInst *> LocalRMWs;
  // TODO: Handle cmpxchg
  // NOTE: AtomicRMW instructions are replaced with other instructions. This
  // cannot be done while iterating over instructions. Load/Store instructions
  // *can* be modified in-place.
  bool Changed = false;
  for (Instruction &I : instructions(F)) {
    if (auto *RMWI = dyn_cast<AtomicRMWInst>(&I);
        RMWI && RMWI->getPointerAddressSpace() == ADDRESS_SPACE_LOCAL) {
      LocalRMWs.push_back(RMWI);
    } else if (auto *LI = dyn_cast<LoadInst>(&I);
               LI && LI->isAtomic() &&
               LI->getPointerAddressSpace() == ADDRESS_SPACE_LOCAL) {
      LI->setAtomic(AtomicOrdering::NotAtomic);
      Changed = true;
    } else if (auto *SI = dyn_cast<StoreInst>(&I);
               SI && SI->isAtomic() &&
               SI->getPointerAddressSpace() == ADDRESS_SPACE_LOCAL) {
      SI->setAtomic(AtomicOrdering::NotAtomic);
      Changed = true;
    }
  }
 
  for (AtomicRMWInst *RMWI : LocalRMWs)
    Changed |= lowerAtomicRMWInst(RMWI);
  return Changed;
}
 
namespace {
class NVPTXAtomicLowerLegacyPass : public FunctionPass {
public:
  static char ID; // Pass ID
  NVPTXAtomicLowerLegacyPass() : FunctionPass(ID) {}
 
  void getAnalysisUsage(AnalysisUsage &AU) const override {
    AU.setPreservesCFG();
  }
 
  StringRef getPassName() const override {
    return "NVPTX lower atomics of local memory";
  }
 
  bool runOnFunction(Function &F) override {
    return lowerLocalMemoryAtomics(F);
  }
};
} // namespace
 
char NVPTXAtomicLowerLegacyPass::ID = 0;
 
INITIALIZE_PASS(NVPTXAtomicLowerLegacyPass, "nvptx-atomic-lower",
                "Lower atomics of local memory to simple load/stores", false,
                false)
 
FunctionPass *llvm::createNVPTXAtomicLowerLegacyPass() {
  return new NVPTXAtomicLowerLegacyPass();
}
 
PreservedAnalyses NVPTXAtomicLowerPass::run(Function &F,
                                            FunctionAnalysisManager &FAM) {
  if (!lowerLocalMemoryAtomics(F))
    return PreservedAnalyses::all();
  return PreservedAnalyses::none().preserveSet<CFGAnalyses>();
}