[llvm-commits] [llvm] r141333 - in /llvm/trunk: include/llvm/Intrinsics.td lib/Analysis/BasicAliasAnalysis.cpp lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h lib/Target/CBackend/CBackend.cpp lib/Transforms/Scalar/LowerAtomic.cpp lib/VMCore/AutoUpgrade.cpp

[Duncan Sands]

Hi Eli,

> --- llvm/trunk/lib/VMCore/AutoUpgrade.cpp (original)
> +++ llvm/trunk/lib/VMCore/AutoUpgrade.cpp Thu Oct  6 18:20:49 2011
> @@ -206,6 +223,80 @@
>
>         // Remove intrinsic.
>         CI->eraseFromParent();
> +    } else if (F->getName().startswith("llvm.atomic.cmp.swap")) {
> +      IRBuilder<>  Builder(C);
> +      Builder.SetInsertPoint(CI->getParent(), CI);
> +      Value *Val = Builder.CreateAtomicCmpXchg(CI->getArgOperand(0),
> +                                               CI->getArgOperand(1),
> +                                               CI->getArgOperand(2),
> +                                               Monotonic);

in your llvm-gcc patch llvm.atomic.cmp.swap was replaced with
CreateAtomicCmpXchg with SequentiallyConsistent, but here you replace with
Monotonic.  Why the difference?  Is it because the gcc builtins have an
implicit memory barrier?

Thanks, Duncan.