[llvm] [PowerPC] enable AtomicExpandImpl::expandAtomicCmpXchg for powerpc (PR #142395)

[Matt Arsenault via llvm-commits]

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@@ -1835,6 +1835,19 @@ let TargetPrefix = "ppc" in {
                       Intrinsic<[],[],[]>;
   def int_ppc_iospace_eieio : ClangBuiltin<"__builtin_ppc_iospace_eieio">,
                               Intrinsic<[],[],[]>;
+  def int_ppc_lbarx :
+    Intrinsic<[llvm_i32_ty], [llvm_ptr_ty],
+              [IntrReadMem, IntrArgMemOnly, IntrNoDuplicate]>;
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arsenm wrote:

You shouldn't really need noduplicate (we should really delete the attribute) 

https://github.com/llvm/llvm-project/pull/142395