RE: [PATCH] Switch vec_init and vec_extract optabs to 2 mode optab to allow extraction of vector from vector or initialization of vector from smaller vectors (PR target/80846)

[Richard Biener <rguenther@suse.de>]

On Tue, 25 Jul 2017, Matthew Fortune wrote:

> Jakub Jelinek <jakub@redhat.com> writes:
> > Bootstrapped/regtested on x86_64-linux and i686-linux, where it improves
> > e.g. the code generation for slp-43.c and slp-45.c testcases.
> > make cc1 tested in cross-compilers to the remaining targets.
> 
> No objections for the MIPS part. I've pointed out this change to Sameera to
> see how/if it will affect her autovectorization branch and whether MIPS MSA
> should define more forms of vec_init/vec_expand in general.

Note the vectorizer will try both variants (punning via integer mode
and vector element) so the change is mostly to get around having very
large integer modes like OImode of AVX512 halves or even larger ones
for ARM SVE.

You should only need to have matching component mode vector part
inits/extracts (and all vector modes are power-of-two size).  Thus
for V8SI have V4SI, V2SI and SI components for init/extracts.
If those are not available the vectorizer will try to pun V8SI
to V2TI and to TImode init/extract or V4DI with DImode, etc.
(that's what the bulk conversion of targets besides x86 should
provide).

Richard.