[cfe-dev] [llvm-dev] RFC: change -fp-contract=off to actually disable FMAs

Scott Manley via cfe-dev cfe-dev at lists.llvm.org
Wed Jul 10 13:09:07 PDT 2019

Numerically identical, sure. But, there are other reasons to disable FMAD
fusion -- namely for performance comparisons.

On Wed, Jul 10, 2019 at 2:52 PM Matt Arsenault <arsenm2 at gmail.com> wrote:

> On Jul 10, 2019, at 15:27, Scott Manley via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
> Is there context I am not aware of for ::Strict and ISD::FMAD? I could see
> value in generating FMAs when its expanded form would be identical -- but
> curious if that was actually the intent or not. If it is, perhaps we could
> allow "Standard/on" to fuse ops if FMAD is available instead of the
> "Strict" level? In any case, we should still have a way to explicitly turn
> off FMAs.
> FMAD Is not FMA, and should not be part of any discussion related to
> fusion rules. It is defined to be identical to the separate fmul and fadd
> -Matt
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