[PATCH] D25291: [AArch64] Optionally use the reciprocal estimation machinery

[Evandro Menezes via llvm-commits]

evandro added a comment.

In https://reviews.llvm.org/D25291#564552, @jmolloy wrote:

> In https://reviews.llvm.org/D25291#564549, @evandro wrote:
>
> > In https://reviews.llvm.org/D25291#564529, @evandro wrote:
> >
> > > In https://reviews.llvm.org/D25291#564496, @jmolloy wrote:
> > >
> > > > If you want to just enable reciprocal selection and test it, then a cl::opt flag seems most appropriate because that's how we enable experimental stuff broad-brush for testing. A CPU feature really isn't right as it ignores the important context that should go into deciding whether to use these instructions (on ARM/AArch64).
> > >
> > >
> > > Adding an option is a good idea to provide a means for users to tap into this feature.
> >
> >
> > Of course, one can always use `-mattr=+use-reciprocal-square-root`.
>
>
> Surely not, because the attribute should merely indicate that use of a reciprocal is *allowed*, not that it is worthwhile.


Enabling the attribute has the effect of using the reciprocal for `sqrt()`, allowing the user to explore if it's worthwhile in his specific case.


Repository:
  rL LLVM

https://reviews.llvm.org/D25291