Re: Do not give realistic estimates for loop with array accesses

[Tom de Vries <Tom_deVries@mentor.com>]

On 30/03/16 14:36, Richard Biener wrote:
> On Wed, 30 Mar 2016, Jan Hubicka wrote:
>
>>> > >
>>> > >You are only changing one place in this file.
>> >
>> >You are right. I am attaching the updated patch which I am re-testing now.
>>> > >
>>> > >The vectorizer already checks this (albeit indirectly):
>>> > >
>>> > >   HOST_WIDE_INT max_niter
>>> > >     = max_stmt_executions_int (LOOP_VINFO_LOOP (loop_vinfo));
>>> > >   if ((LOOP_VINFO_NITERS_KNOWN_P (loop_vinfo)
>>> > >        && (LOOP_VINFO_INT_NITERS (loop_vinfo) < vectorization_factor))
>>> > >       || (max_niter != -1
>>> > >           && (unsigned HOST_WIDE_INT) max_niter < vectorization_factor))
>>> > >     {
>>> > >       if (dump_enabled_p ())
>>> > >         dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
>>> > >                          "not vectorized: iteration count smaller than "
>>> > >                          "vectorization factor.\n");
>>> > >       return false;
>>> > >     }
>> >
>> >Yes, but one tests only vectorization_factor and other min_profitable_estimate
>> >which probably should be greater than vectorization_factor.
>> >
>> >The check above should therefore become redundant.  My reading of the code is
>> >that min_profiltable_estimate is computed after the check above, so it is
>> >probably an useful shortcut and the message is also bit more informative.
>> >I updated the later test to use max_niter variable once it is computed.
>> >
>> >OK with those changes assuming testing passes?
> Ok.

This patch caused PR70577 - 'tree-ssa/prefetch-5.c scan-tree-dump-times 
aprefetch failures' ( https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70577 ).

Thanks,
- Tom