[llvm] AMDGPU: Add codegen for atomicrmw operations usub_cond and usub_sat (PR #141068)

[Matt Arsenault via llvm-commits]

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+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -global-isel -mtriple=amdgcn-amd-amdhsa -mcpu=gfx1030 < %s | FileCheck %s -check-prefix=GFX10-GISEL
+; RUN: llc -global-isel -mtriple=amdgcn-amd-amdhsa -mcpu=gfx1031 < %s | FileCheck %s -check-prefix=GFX10-GISEL
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arsenm wrote:

I don't think testing both 1030 and 1031 is useful. It should test the older subtargets too 

https://github.com/llvm/llvm-project/pull/141068