[PATCH] D129734: [InstCombine] Canonicalize GEP of GEP by swapping constant-indexed GEP to the front

[Nikita Popov via Phabricator via llvm-commits]

nikic added a comment.

I think this will do worse in practice, because it breaks GVN. Imagine you have accesses like `ary[i].x`, `ary[i].y`, `ary[i].z` represented with two GEPs. If constants are canonicalized to the end, then the `ary[i]` GEP is the same all three times and can be CSEd/GVNd. If the constants are canonicalized to the start, then these all become distinct GEPs on different bases.


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https://reviews.llvm.org/D129734