[PATCH] D85969: [SCEV] Model (xor (shl x, C), (-1 << C)) as (shl (xor x, -1), C)

Fri Aug 14 06:00:45 PDT 2020

spatel added a comment.

I don't have much experience with SCEV either, but I think your draft change for instcombine made sense:
https://bugs.llvm.org/show_bug.cgi?id=47136#c8

As hinted there, that's the same direction as:
D32255 <https://reviews.llvm.org/D32255> / rG23bd33c6acc4 <https://reviews.llvm.org/rG23bd33c6acc4fa0ddc097d3d0767860cc014f6e0>

So I'm not sure if we would consider this a worthwhile improvement independently and still make a change to SCEV or only change instcombine (or if there's some reason to *not* change instcombine, I'd like to understand that).

Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D85969/new/

https://reviews.llvm.org/D85969