[PATCH] D154678: [InstCombine] Fold IEEE `fmul`/`fdiv` by Pow2 to `add`/`sub` of exp

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added a comment.

My current thought is this is a worse canonical form for floating point operations and would be better done in codegen. This is going to interfere with FMA matching, plus computeKnownFPClass is going to give up on the integer ops and cast.

This is also similar to a codegen combine I’ve been planning on doing to fold fmul by power of 2 to ldexp. That has the same FMA interference properties, but is easier to deal with. Have you considered introducing ldexp instead and breaking that in codegen if ldexp isn’t legal?


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https://reviews.llvm.org/D154678