[llvm] [InstCombine] Canonicalize non-i8 gep of mul to i8 (PR #96606)

[David Green via llvm-commits]

davemgreen wrote:

> Looks reasonable to me. At least to start with, I would limit this to the one-use case, to minimize impact. This kind of change tends to have fallout...

Yeah that sounds good. You are right there can be quite a lot of fallout, even from the limited version of the canonicalization. I haven't seen anything in my results that was worse that didn't turn out to be noise, but no set of benchmarks can capture every case.

https://github.com/llvm/llvm-project/pull/96606