[llvm] [InstCombine] Split GEPs with multiple variable indices (PR #137297)

[Nikita Popov via llvm-commits]

nikic wrote:

> FYI, we see a significant regression (50-70%) of the https://github.com/llvm/llvm-test-suite/blob/main/SingleSource/Benchmarks/Stanford/FloatMM.c benchmark after this commit. It's visible on both aarch64 and x86-64. This benchmark is not representative of any real workloads we're interested in, AFAIU, so I'm not particularly concerned, but maybe you want to double-check that there's no hidden problems here.

I can't reproduce this. In which configuration?

Looking at the assembly diff, the only relevant difference I see is a loop getting unrolled, but doesn't seem to have any effect on performance.

https://github.com/llvm/llvm-project/pull/137297