[llvm] [AMDGPU] Add dereferenceable retAttr to a call to llvm.amdgcn.implicitarg.ptr (PR #182206)

[Matt Arsenault via llvm-commits]

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@@ -0,0 +1,67 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 6
+; RUN: opt -S -passes='instcombine' -mtriple=amdgcn-amd-amdhsa < %s | FileCheck %s --check-prefix=DEREF
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arsenm wrote:

s/DEREF/AMDHSA. Also add a -mesa-mesa3d check to compare the values 

https://github.com/llvm/llvm-project/pull/182206