[llvm] r204972 - [X86][Vector Cost Model] Add a comment to explain the workaround

[Eric Christopher]

On Mar 27, 2014 4:21 PM, "Quentin Colombet" <qcolombet at apple.com> wrote:
>
>
> On Mar 27, 2014, at 4:15 PM, Eric Christopher <echristo at gmail.com> wrote:
>
> > On Thu, Mar 27, 2014 at 3:27 PM, Quentin Colombet <qcolombet at apple.com>
wrote:
> >> Author: qcolombet
> >> Date: Thu Mar 27 17:27:41 2014
> >> New Revision: 204972
> >>
> >> URL: http://llvm.org/viewvc/llvm-project?rev=204972&view=rev
> >> Log:
> >> [X86][Vector Cost Model] Add a comment to explain the workaround
> >> in my previous commit (r204884).
> >>
> >> <rdar://problem/16381225>
> >
> > Thanks for following up on this Quentin!
> Sure!
>
> If Adam did not pushed for a comment, I wouldn't have known I was working
around a bug :).
>

Yep. Why I pushed Jim as well. :)

-eric

> -Quentin
>
> >
> > -eric
> >
> >>
> >> Modified:
> >>    llvm/trunk/lib/Target/X86/X86TargetTransformInfo.cpp
> >>
> >> Modified: llvm/trunk/lib/Target/X86/X86TargetTransformInfo.cpp
> >> URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86TargetTransformInfo.cpp?rev=204972&r1=204971&r2=204972&view=diff
> >>
==============================================================================
> >> --- llvm/trunk/lib/Target/X86/X86TargetTransformInfo.cpp (original)
> >> +++ llvm/trunk/lib/Target/X86/X86TargetTransformInfo.cpp Thu Mar 27
17:27:41 2014
> >> @@ -512,6 +512,11 @@ unsigned X86TTI::getCastInstrCost(unsign
> >>     { ISD::UINT_TO_FP,  MVT::v4f64, MVT::v4i8,  2 },
> >>     { ISD::UINT_TO_FP,  MVT::v4f64, MVT::v4i16, 2 },
> >>     { ISD::UINT_TO_FP,  MVT::v4f64, MVT::v4i32, 6 },
> >> +    // The generic code to compute the scalar overhead is currently
broken.
> >> +    // Workaround this limitation by estimating the scalarization
overhead
> >> +    // here. We have roughly 10 instructions per scalar element.
> >> +    // Multiply that by the vector width.
> >> +    // FIXME: remove that when PR19268 is fixed.
> >>     { ISD::UINT_TO_FP,  MVT::v2f64, MVT::v2i64, 2*10 },
> >>     { ISD::UINT_TO_FP,  MVT::v4f64, MVT::v4i64, 4*10 },
> >>
> >>
> >>
> >> _______________________________________________
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>
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