[llvm] [Xtensa] Implement Xtensa S32C1I Option and atomics lowering. (PR #137134)

[Matt Arsenault via llvm-commits]

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@@ -175,6 +175,40 @@ XtensaTargetLowering::XtensaTargetLowering(const TargetMachine &TM,
   setOperationAction(ISD::VACOPY, MVT::Other, Custom);
   setOperationAction(ISD::VAEND, MVT::Other, Expand);
 
+    // to have the best chance and doing something good with fences custom lower
+  // them
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arsenm wrote:

Remove or replace comment with something more informative about why it needs custom lowering 

https://github.com/llvm/llvm-project/pull/137134