[clang] [llvm] [InstCombine] Strip leading zero indices from GEP (PR #155415)

[David Green via cfe-commits]

davemgreen wrote:

Oh - I was about to put up https://github.com/llvm/llvm-project/commit/fd286bdd68f064d6ccbb075c1e2f4bbd57dc4030. That was only going to try with array types, not with vectors too, and I believe the only other semi-useful part was some DA tests I had tried adding without array indices (which looked fine for all the ones I tested).

The differences I have seen have mostly been extra hoisting causing extra unrolling. I would be interested in if @dtcxzyw finds anything more.

https://github.com/llvm/llvm-project/pull/155415