[llvm] [AMDGPU] Omit umin on ctlz/cttz if operand is non-zero. (PR #79127)

[Jay Foad via llvm-commits]

jayfoad wrote:

> However, during legalisation we introduce an OR of the loaded value with a constant.

At that point the cttz should have been replaced with cttz_zero_undef. Does #92514 work for you?

https://github.com/llvm/llvm-project/pull/79127