[RFC PATCH, i386]: Autovectorize 8-byte vectors

[Jakub Jelinek]

On Wed, Jun 26, 2019 at 12:19:28PM +0200, Uros Bizjak wrote:
> > The patch isn't correct if TARGET_MMX_WITH_SSE, but not TARGET_AVX, because
> > in that case it will push only that 8 and nothing else, while you really
> > want to have 16 and 8 in that order, so that it tries to vectorize first
> > with 16-byte vectors and fall back to 8-byte.  The hook is supposed to
> > either push nothing at all, then only one vector size is tried,
> > one derived from preferred_simd_mode, or push all possible vectorization
> > sizes to be tried.
> 
> Thanks for the explanation and the patch!

It is even documented that way:
 "If the mode returned by @code{TARGET_VECTORIZE_PREFERRED_SIMD_MODE} is not\n\
the only one that is worth considering, this hook should add all suitable\n\
vector sizes to @var{sizes}, in order of decreasing preference.  The first\n\
one should be the size of @code{TARGET_VECTORIZE_PREFERRED_SIMD_MODE}.\n\
If @var{all} is true, add suitable vector sizes even when they are generally\n\
not expected to be worthwhile.\n\

	Jakub