[llvm-branch-commits] [llvm] AMDGPU: Custom expand flat cmpxchg which may access private (PR #109410)

[Eli Friedman via llvm-branch-commits]

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@@ -25,20 +25,29 @@ bool llvm::lowerAtomicCmpXchgInst(AtomicCmpXchgInst *CXI) {
   Value *Cmp = CXI->getCompareOperand();
   Value *Val = CXI->getNewValOperand();
 
-  LoadInst *Orig =
-      Builder.CreateAlignedLoad(Val->getType(), Ptr, CXI->getAlign());
-  Value *Equal = Builder.CreateICmpEQ(Orig, Cmp);
-  Value *Res = Builder.CreateSelect(Equal, Val, Orig);
-  Builder.CreateAlignedStore(Res, Ptr, CXI->getAlign());
+  auto [Orig, Equal] =
+      buildAtomicCmpXchgValue(Builder, Ptr, Cmp, Val, CXI->getAlign());
 
-  Res = Builder.CreateInsertValue(PoisonValue::get(CXI->getType()), Orig, 0);
+  Value *Res =
+      Builder.CreateInsertValue(PoisonValue::get(CXI->getType()), Orig, 0);
   Res = Builder.CreateInsertValue(Res, Equal, 1);
 
   CXI->replaceAllUsesWith(Res);
   CXI->eraseFromParent();
   return true;
 }
 
+std::pair<Value *, Value *>
+llvm::buildAtomicCmpXchgValue(IRBuilderBase &Builder, Value *Ptr, Value *Cmp,
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efriedma-quic wrote:

Putting "atomic" in the name here is a little strange; this isn't atomic.

https://github.com/llvm/llvm-project/pull/109410