[llvm-dev] Suggestions on code generation for SIMD

Linchuan Chen via llvm-dev llvm-dev at lists.llvm.org
Tue Jan 9 20:59:17 PST 2018


Thanks Serge! This means for every new intrinsic set, a systematic change
should be made to LLVM to support the new intrinsic set, right? The change
should include frontend change, IR instruction set change, as well as low
level code generation changes?

On Tue, Jan 9, 2018 at 12:39 AM, serge guelton via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> >     The vast majority of the time people will rely on source level
> pragmas [1],
> >     LLVM IR is designed to be machine friendly, not something intended
> for
> >     users to manually edit themselves. You can do it, but it’s tedious
> and
> >     error prone. If you need more control over the vectorisation than the
> >     pragmas allow, then the C intrinsics are the best choice.
> >
> >     Amara
> >
> >     [1] http://clang.llvm.org/docs/LanguageExtensions.html#
> >     extensions-for-loop-hint-optimizations
>
> A large portion of user still use intrinsics too, as provided in
> avxintrin.h and the likes. They are then lowered to a single/few
> llvm instructions with vector operands.
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-- 
Sincerely,
Linchuan
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