[PATCH] Enable fma and f16c features when avx512f is enabled.

[Craig Topper]

I think that makes sense. We need to enable ISD::FMA for the smaller types
when AVX512 is enabled. Probably need to add AVX512 in PerformFMACombine
and isFMAFasterThanFMulAndFAdd as well.

On Tue, Jun 23, 2015 at 1:23 PM, Ahmed Bougacha <ahmed.bougacha at gmail.com>
wrote:

> In http://reviews.llvm.org/D10617#192429, @craig.topper wrote:
>
> > Are the 512-bit intrinsics in clang's headers qualified with F16C and FMA
> >  defines? They don't seem to be in gcc's headers. And gcc doesn't seem to
> >  auto enable FMA or F16C when avx512 is specified.
> >
> > Similar question for the instructions in llvm.
>
>
> They're not?
>
> But, if that's what you're getting at: if the defines have a 1-to-1
> mapping with the intrinsics/headers (I think they do?), then on second
> thought, this isn't the right fix: +avx512f says nothing about whether we
> support FMA/F16C intrinsics, only the AVX512F ones.
>
> Then the actual issue here is that, for fma and f16c, LLVM codegen relies
> on +fma/+f16c only to mark say f32 ISD::FMA as legal, and generate
> X86ISD::FMADD.  Both of which are necessary to generate even the AVX512F
> instruction, and this makes it impossible with +avx512f alone.
> Does that make sense?  If so I'll post a patch!
>
> -Ahmed
>
>
> http://reviews.llvm.org/D10617
>
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-- 
~Craig
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