[llvm] [AMDGPU] Support divergent sized dynamic alloca (PR #121148)

[via llvm-commits]

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+; NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 5
+; RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx900 -stop-after=amdgpu-isel < %s | FileCheck -check-prefix=GFX9 %s
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easyonaadit wrote:

This test points are similar to `llvm/test/CodeGen/AMDGPU/dynamic_stackalloc.ll`
This test was added to check the selection, more specifically wave reduction intrinsic. 

https://github.com/llvm/llvm-project/pull/121148