[llvm] [LV] Fix handleFirstArgMinOrMax to use 0 as identity element for UMax/SMax (PR #192054)

[Akash Agrawal via llvm-commits]

akashagrwl wrote:

> > We have confirmed this is causing wrong-code generation in a real-world signal processing benchmark (argmax with strict > predicate, returning 0 instead of the correct index). This PR fixes the issue
> 
> If you have a loop that reproduces the issue end-to-end, it would be great if you could add it here
> 
> https://github.com/llvm/llvm-test-suite/blob/main/SingleSource/UnitTests/Vectorizer/argmin-argmax-int.cpp

I have submitted a new issue with additional details at https://github.com/llvm/llvm-project/issues/194566.

https://github.com/llvm/llvm-project/pull/192054