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

[Nikita Popov via llvm-commits]

nikic wrote:

> Given this is in the `preopt` IR, the change would occur in an even earlier stage, right? I'll see if I can get some IR out of whatever stage that may be.

Yes, you're currently dumping the pre-LTO IR, but we'd want the full optimized one produced by the compiler. (Should be possible to get it with `-S -emit-llvm -Xclang -disable-llvm-optzns`.)

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Does anyone know which transform is capable of converting a load from a constant global into a dynamic extract from a vector constant? I tried and failed to reproduce that behavior on simpler test cases.

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