diff options
Diffstat (limited to 'gcc/loop-unroll.c')
-rw-r--r-- | gcc/loop-unroll.c | 28 |
1 files changed, 13 insertions, 15 deletions
diff --git a/gcc/loop-unroll.c b/gcc/loop-unroll.c index 2398e6d..92e3c1a 100644 --- a/gcc/loop-unroll.c +++ b/gcc/loop-unroll.c @@ -1228,7 +1228,6 @@ static void decide_peel_simple (struct loop *loop, int flags) { unsigned npeel; - struct niter_desc *desc; double_int iterations; if (!(flags & UAP_PEEL)) @@ -1253,20 +1252,17 @@ decide_peel_simple (struct loop *loop, int flags) return; } - /* Check for simple loops. */ - desc = get_simple_loop_desc (loop); - - /* Check number of iterations. */ - if (desc->simple_p && !desc->assumptions && desc->const_iter) - { - if (dump_file) - fprintf (dump_file, ";; Loop iterates constant times\n"); - return; - } - /* Do not simply peel loops with branches inside -- it increases number - of mispredicts. */ - if (num_loop_branches (loop) > 1) + of mispredicts. + Exception is when we do have profile and we however have good chance + to peel proper number of iterations loop will iterate in practice. + TODO: this heuristic needs tunning; while for complette unrolling + the branch inside loop mostly eliminates any improvements, for + peeling it is not the case. Also a function call inside loop is + also branch from branch prediction POV (and probably better reason + to not unroll/peel). */ + if (num_loop_branches (loop) > 1 + && profile_status != PROFILE_READ) { if (dump_file) fprintf (dump_file, ";; Not peeling, contains branches\n"); @@ -1435,7 +1431,9 @@ decide_unroll_stupid (struct loop *loop, int flags) } /* Do not unroll loops with branches inside -- it increases number - of mispredicts. */ + of mispredicts. + TODO: this heuristic needs tunning; call inside the loop body + is also relatively good reason to not unroll. */ if (num_loop_branches (loop) > 1) { if (dump_file) |