[PATCH] D63992: [InstCombine] Y - ~X --> X + Y + 1 fold (PR42457)

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a comment.

Yes, we should probably teach DAGCombine to choose the right form for each target/type.

It seems reasonable to prefer `x+(y+1)` over `x-(-1-y)`, for reassociation etc.  It's possible there could be some bad interaction at the interface between logical and arithmetic operations, which makes us miss some important optimization, but that doesn't seem likely to me.


Repository:
  rL LLVM

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https://reviews.llvm.org/D63992