[llvm] [clang] [CodeGen] Port AtomicExpand to new Pass Manager (PR #71220)

[Matt Arsenault via llvm-commits]

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@@ -340,7 +342,33 @@ bool AtomicExpand::runOnFunction(Function &F) {
   return MadeChange;
 }
 
-bool AtomicExpand::bracketInstWithFences(Instruction *I, AtomicOrdering Order) {
+bool AtomicExpandLegacy::runOnFunction(Function &F) {
+  if (skipFunction(F))
+    return false;
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arsenm wrote:

This should not use skipFunction, it's a mandatory lowering pass. It's not part of the current code 

https://github.com/llvm/llvm-project/pull/71220