[llvm] reduce over divergent mask (PR #133228)

[Aniket Lal via llvm-commits]

lalaniket8 wrote:

Command to run :

./build/bin/llc -mtriple=amdgcn -mcpu=tonga -global-isel=0 -print-after="finalize-isel" -verify-machineinstrs < /home/anikelal/upstream_llvm_project/llvm-project/newreduceumax.ll 2>&1 | tee temp.ll

https://github.com/llvm/llvm-project/pull/133228