[PATCH] D14909: [X86][FMA] Optimize FNEG(FMUL) Patterns

[Sanjay Patel via llvm-commits]

spatel added a comment.

In http://reviews.llvm.org/D14909#298770, @scanon wrote:

> In http://reviews.llvm.org/D14909#298759, @spatel wrote:
>
> > Can we assume default rounding for now, change the operand to X86::FNMSUB, remove the nsz check, and leave a 'TODO' comment to revisit this after rounding mode support is added? I think it would be better to have this transform be more general if we can.
>
>
> I would *really* prefer not to.  Not having rounding-mode support means that we should do the conservative thing.  Once we have the ability to do the right thing, we can make the default more aggressive.


Ok. We should have a comment here to explain the logic then.
Would it still be better to use FNMSUB now even with the nsz check, so we're minimizing codegen differences after we have rounding-mode support?


Repository:
  rL LLVM

http://reviews.llvm.org/D14909