[PATCH] Disable loop unrolling in loop vectorization pass when VF is 1 on x86

[Renato Golin]

Hi Wei,

The example you have shown would produce bad vectorized code on any architecture, I don't think anything you said (multiple unrolling and prologue loops) would make much difference on other archs. Maybe you're trying to fix a global problem locally, and creating some unnecessary constraints for the cases that do work.

However, your performance improvements are really impressive, so I think we ought to check other archs, and maybe try to detect the problematic case on a generic level?

cheers,
--renato


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http://reviews.llvm.org/D9515

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