[llvm] [IR][AtomicExpand] Add elementwise modifier to atomicrmw; automatically expand for all targets (PR #189517)

[Matt Arsenault via llvm-commits]

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@@ -0,0 +1,16 @@
+; RUN: llvm-as %s -o - | llvm-dis | FileCheck %s
+; RUN: llvm-as %s -o - | verify-uselistorder
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arsenm wrote:

Should this also be added to compatibility.ll 

https://github.com/llvm/llvm-project/pull/189517