------- Comment #13 from changpeng dot fang at amd dot com 2010-06-01 19:59
-------
(In reply to comment #12)
> Ok. So I will let you continue to look into that and wait for your results?
>
> Do you have any feedback on separate.patch and its influence on performance?
>
+ for (; groups; groups = groups->next)
+ for (ref = groups->refs; ref; ref = ref->next)
+ {
+ if (cst_and_fits_in_hwi (ref->group->step))
+ continue;
+ if (!ref->issue_prefetch_p)
+ continue;
+ insn_to_prefetch_ratio = (unroll_factor * ninsns) / prefetch_count;
+ if (insn_to_prefetch_ratio < MIN_INSN_TO_SPECULATIVE_PREFETCH)
+ {
+ ref->issue_prefetch_p = false;
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file,
+ "Ignoring %p-- insn to prefetch ratio (%d) too small\n",
+ (void *) ref, insn_to_prefetch_ratio);
+ }
+ }
+ }
The patch should fix the tonto regression caused by non-constant step
prefetching. It is just that you should move the computation and comparison
outside (before) the loop and the debug dump after the loop.
I am just thinking that for such loop, we should do nothing: non-non-temporal
stores and no constant step prefetching because nothing could be trusted.
I am doing some experiemnts and let you know what I could find. Thanks.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44297
