vendor/llvm-project/llvmorg-15-init-15358-g53dc0f107877

1 files changed, 93 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Utils/LowerAtomic.cpp b/llvm/lib/Transforms/Utils/LowerAtomic.cpp
new file mode 100644
index 000000000000..8641581c8039
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+++ b/llvm/lib/Transforms/Utils/LowerAtomic.cpp
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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/Utils/LowerAtomic.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+using namespace llvm;
+
+#define DEBUG_TYPE "loweratomic"
+
+bool llvm::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;
+}
+
+Value *llvm::buildAtomicRMWValue(AtomicRMWInst::BinOp Op,
+                                 IRBuilderBase &Builder, Value *Loaded,
+                                 Value *Inc) {
+  Value *NewVal;
+  switch (Op) {
+  case AtomicRMWInst::Xchg:
+    return Inc;
+  case AtomicRMWInst::Add:
+    return Builder.CreateAdd(Loaded, Inc, "new");
+  case AtomicRMWInst::Sub:
+    return Builder.CreateSub(Loaded, Inc, "new");
+  case AtomicRMWInst::And:
+    return Builder.CreateAnd(Loaded, Inc, "new");
+  case AtomicRMWInst::Nand:
+    return Builder.CreateNot(Builder.CreateAnd(Loaded, Inc), "new");
+  case AtomicRMWInst::Or:
+    return Builder.CreateOr(Loaded, Inc, "new");
+  case AtomicRMWInst::Xor:
+    return Builder.CreateXor(Loaded, Inc, "new");
+  case AtomicRMWInst::Max:
+    NewVal = Builder.CreateICmpSGT(Loaded, Inc);
+    return Builder.CreateSelect(NewVal, Loaded, Inc, "new");
+  case AtomicRMWInst::Min:
+    NewVal = Builder.CreateICmpSLE(Loaded, Inc);
+    return Builder.CreateSelect(NewVal, Loaded, Inc, "new");
+  case AtomicRMWInst::UMax:
+    NewVal = Builder.CreateICmpUGT(Loaded, Inc);
+    return Builder.CreateSelect(NewVal, Loaded, Inc, "new");
+  case AtomicRMWInst::UMin:
+    NewVal = Builder.CreateICmpULE(Loaded, Inc);
+    return Builder.CreateSelect(NewVal, Loaded, Inc, "new");
+  case AtomicRMWInst::FAdd:
+    return Builder.CreateFAdd(Loaded, Inc, "new");
+  case AtomicRMWInst::FSub:
+    return Builder.CreateFSub(Loaded, Inc, "new");
+  default:
+    llvm_unreachable("Unknown atomic op");
+  }
+}
+
+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 = buildAtomicRMWValue(RMWI->getOperation(), Builder, Orig, Val);
+  Builder.CreateStore(Res, Ptr);
+  RMWI->replaceAllUsesWith(Orig);
+  RMWI->eraseFromParent();
+  return true;
+}