[clang] [llvm] [AMDGPU] Adding the amdgpu-num-work-groups function attribute (PR #79035)

[Matt Arsenault via cfe-commits]

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+; RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx900 < %s | FileCheck %s
+
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arsenm wrote:

Missing a test for the various IR attribute parsing error conditions 

https://github.com/llvm/llvm-project/pull/79035