[llvm] r214042 - [x86] Add a much more powerful framework for combining x86 shuffle

Chandler Carruth chandlerc at gmail.com
Sun Jul 27 18:41:20 PDT 2014


On Sun, Jul 27, 2014 at 6:37 PM, Chandler Carruth <chandlerc at gmail.com>
wrote:

> and can't be


Ah, with one exception: if you used the builtins or llvm intrinsics
directly to force the emission of pshufd, pshuflw, and pshufhw in long
chains, you could trigger this. But you can't even trigger it really from
_mm_shuffle_epi32, _mm_shufflelo_epi16, or _mm_shufflehi_epi16 because
those lower through generic shuffles in LLVM.... =/

Anyways, do let me know if you're seeing regressions due to this.. I'd be
fascinated with how, and its easy to put it too behind the same flag.
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