diff options
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/ChangeLog | 7 | ||||
| -rw-r--r-- | gcc/tree-ssa-loop-prefetch.c | 14 |
2 files changed, 20 insertions, 1 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 6236c9e..5467fa9 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,5 +1,12 @@ 2010-05-07 Changpeng Fang <changpeng.fang@amd.com> + * tree-ssa-loop-prefetch.c (TRIP_COUNT_TO_AHEAD_RATIO): New. + (is_loop_prefetching_profitable): Do not insert prefetches + when the trip count is not at least TRIP_COUNT_TO_AHEAD_RATIO + times the prefetch ahead distance. + +2010-05-07 Changpeng Fang <changpeng.fang@amd.com> + * tree-ssa-loop-prefetch.c (is_loop_prefetching_profitable): Account for loop unrolling in the insn-to-prefetch ratio heuristic. (loop_prefetch_arrays): Pass to is_loop_prefetching_profitable diff --git a/gcc/tree-ssa-loop-prefetch.c b/gcc/tree-ssa-loop-prefetch.c index 38d8f23..7497616 100644 --- a/gcc/tree-ssa-loop-prefetch.c +++ b/gcc/tree-ssa-loop-prefetch.c @@ -199,6 +199,18 @@ along with GCC; see the file COPYING3. If not see #define FENCE_FOLLOWING_MOVNT NULL_TREE #endif +/* It is not profitable to prefetch when the trip count is not at + least TRIP_COUNT_TO_AHEAD_RATIO times the prefetch ahead distance. + For example, in a loop with a prefetch ahead distance of 10, + supposing that TRIP_COUNT_TO_AHEAD_RATIO is equal to 4, it is + profitable to prefetch when the trip count is greater or equal to + 40. In that case, 30 out of the 40 iterations will benefit from + prefetching. */ + +#ifndef TRIP_COUNT_TO_AHEAD_RATIO +#define TRIP_COUNT_TO_AHEAD_RATIO 4 +#endif + /* The group of references between that reuse may occur. */ struct mem_ref_group @@ -1585,7 +1597,7 @@ is_loop_prefetching_profitable (unsigned ahead, HOST_WIDE_INT est_niter, return insn_to_prefetch_ratio >= MIN_INSN_TO_PREFETCH_RATIO; } - if (est_niter <= (HOST_WIDE_INT) ahead) + if (est_niter < (HOST_WIDE_INT) (TRIP_COUNT_TO_AHEAD_RATIO * ahead)) { if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, |