New hook is related to vector instructions only. Vector instructions could be sequential in pipeline, but scalar - parallel. For x86 architectures TARGET_SCHED_REASSOC_WIDTH does not give required differentiation. General hooks could be potentially reused in other algorithms/by other architectures.
Thanks, Evgeny On Thu, Jun 5, 2014 at 2:04 PM, Ramana Radhakrishnan <ramana....@googlemail.com> wrote: > On Wed, May 28, 2014 at 2:09 PM, Evgeny Stupachenko <evstu...@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 <evstu...@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
