1 files changed, 142 insertions, 0 deletions
diff --git a/contrib/llvm/lib/Transforms/Scalar/LowerAtomic.cpp b/contrib/llvm/lib/Transforms/Scalar/LowerAtomic.cpp
new file mode 100644
index 0000000..7419a65
--- /dev/null
+++ b/contrib/llvm/lib/Transforms/Scalar/LowerAtomic.cpp
@@ -0,0 +1,142 @@
+//===- LowerAtomic.cpp - Lower atomic intrinsics --------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass lowers atomic intrinsics to non-atomic form for use in a known
+// non-preemptible environment.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "loweratomic"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/Function.h"
+#include "llvm/IRBuilder.h"
+#include "llvm/IntrinsicInst.h"
+#include "llvm/Pass.h"
+using namespace llvm;
+
+static bool LowerAtomicCmpXchgInst(AtomicCmpXchgInst *CXI) {
+  IRBuilder<> Builder(CXI->getParent(), CXI);
+  Value *Ptr = CXI->getPointerOperand();
+  Value *Cmp = CXI->getCompareOperand();
+  Value *Val = CXI->getNewValOperand();
+
+  LoadInst *Orig = Builder.CreateLoad(Ptr);
+  Value *Equal = Builder.CreateICmpEQ(Orig, Cmp);
+  Value *Res = Builder.CreateSelect(Equal, Val, Orig);
+  Builder.CreateStore(Res, Ptr);
+
+  CXI->replaceAllUsesWith(Orig);
+  CXI->eraseFromParent();
+  return true;
+}
+
+static bool LowerAtomicRMWInst(AtomicRMWInst *RMWI) {
+  IRBuilder<> Builder(RMWI->getParent(), RMWI);
+  Value *Ptr = RMWI->getPointerOperand();
+  Value *Val = RMWI->getValOperand();
+
+  LoadInst *Orig = Builder.CreateLoad(Ptr);
+  Value *Res = NULL;
+
+  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;
+  }
+  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(NotAtomic);
+  return true;
+}
+
+static bool LowerStoreInst(StoreInst *SI) {
+  SI->setAtomic(NotAtomic);
+  return true;
+}
+
+namespace {
+  struct LowerAtomic : public BasicBlockPass {
+    static char ID;
+    LowerAtomic() : BasicBlockPass(ID) {
+      initializeLowerAtomicPass(*PassRegistry::getPassRegistry());
+    }
+    bool runOnBasicBlock(BasicBlock &BB) {
+      bool Changed = false;
+      for (BasicBlock::iterator DI = BB.begin(), DE = BB.end(); DI != DE; ) {
+        Instruction *Inst = DI++;
+        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;
+    }
+  };
+}
+
+char LowerAtomic::ID = 0;
+INITIALIZE_PASS(LowerAtomic, "loweratomic",
+                "Lower atomic intrinsics to non-atomic form",
+                false, false)
+
+Pass *llvm::createLowerAtomicPass() { return new LowerAtomic(); }