[llvm] [AMDGPU] Add IR-level pass to rewrite away address space 7 (PR #77952)

[Matt Arsenault via llvm-commits]

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@@ -352,3 +352,107 @@ loop.exit:
 exit:
   ret float %sum
 }
+
+;; Test that the optimization works correctly for phi nodes that repeat the same
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arsenm wrote:

Not an optimization 

https://github.com/llvm/llvm-project/pull/77952