[llvm] [PowerPC] support branch hint for AtomicExpandImpl::expandAtomicCmpXchg (PR #152366)

[Matt Arsenault via llvm-commits]

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@@ -12816,6 +12817,11 @@ Value *PPCTargetLowering::emitStoreConditional(IRBuilderBase &Builder,
   return Builder.CreateXor(Call, Builder.getInt32(1));
 }
 
+MDNode *PPCTargetLowering::getTrueBranchHintWeightForAtomicCmpXchgg(
+    LLVMContext &Ctx) const {
+  return MDBuilder(Ctx).createLikelyBranchWeights();
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arsenm wrote:

The details of what the target is going to do with the metadata is unimportant, this is a generic branch likely hint. 

https://github.com/llvm/llvm-project/pull/152366