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Re: [PATCH, PR52252] Alternative way of vectorization for load groups of size 2 and 3.


On Wed, May 28, 2014 at 2:09 PM, Evgeny Stupachenko <evstupac@gmail.com> wrote:
> Hi,
>
> The patch introduces alternative way of permutations for load groups
> of size 2 and 3 which should be faster on architectures with low
> parallelism.
> The patch gives 2 times gain on Silvermont to the test from PR52252
> (in addition to already committed 3 times gain).
>
> Patch passes bootstrap on x86. Make check is in progress.

Why do we need a new hook ? Can't you derive this information from
something which is equally badly named TARGET_SCHED_REASSOC_WIDTH
though used in the reassociation logic but also serves a similar
purpose ?

Also the documentation of this hook is incomplete at best and wrong at
worst as this is not applied everywhere in the vectorizer but just for
this special case for load store permuting. Implying this is useful
everywhere in the vectorizer does not appear to be correct.

regards
Ramana




>
> ChangeLog:
>
> 2014-05-28  Evgeny Stupachenko  <evstupac@gmail.com>
>
>         * config/i386/i386.c (ix86_have_vector_parallel_execution): New.
>         (TARGET_VECTORIZE_HAVE_VECTOR_PARALLEL_EXECUTION): New.
>         * config/i386/i386.h (TARGET_VECTOR_PARALLEL_EXECUTION): New.
>         * config/i386/x86-tune.def (X86_TUNE_VECTOR_PARALLEL_EXECUTION): New.
>         * target.def (have_vector_parallel_execution): New.
>         * doc/tm.texi.in (have_vector_parallel_execution)): New.
>         * doc/tm.texi: Regenerate.
>         * targhooks.c (default_have_vector_parallel_execution): New.
>         * tree-vect-data-refs.c (vect_shift_permute_load_chain): New.
>         Introduces alternative way of loads group permutaions.
>         (vect_transform_grouped_load): Try alternative way of permutaions.
>
> Evgeny


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