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

[Ahmed Bougacha]

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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