[PATCH] D32596: [DAGCombine] Transform (fadd A, (fmul B, -2.0)) -> (fsub A, (fadd B, B)).
Sanjay Patel via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Thu May 4 11:09:50 PDT 2017
spatel added a comment.
In https://reviews.llvm.org/D32596#746288, @mcrosier wrote:
> While InstCombine does nothing, the reassociation pass will canonicalize to
>
> (fsub A, (fmul/fdiv B, -C)) -> (fadd A, (fmul/fdiv B, C))
> (fadd A, (fmul/fdiv B, -C)) -> (fsub A, (fmul/fdiv B, C))
Thanks for checking those out. I haven't looked at the reassociation pass very much. I'm surprised to see it flip a constant's sign and create an fsub rather than fadd. Any ideas why that is a good thing to do?
Repository:
rL LLVM
https://reviews.llvm.org/D32596
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