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| author | Jan Hubicka <hubicka@gcc.gnu.org> | 2012-10-23 15:15:58 +0000 |
|---|---|---|
| committer | Jan Hubicka <hubicka@gcc.gnu.org> | 2012-10-23 15:15:58 +0000 |
| commit | 6acf25e4b380e5ad738ffe2830a71635bc5230d1 (patch) | |
| tree | 0f15c07165dd8eb1e94225c4f167441e61fadd00 /gcc/loop-unroll.c | |
| parent | 2dc34a12e3edfc32133e6e000155ea7d66c9c706 (diff) | |
| download | gcc-6acf25e4b380e5ad738ffe2830a71635bc5230d1.zip gcc-6acf25e4b380e5ad738ffe2830a71635bc5230d1.tar.gz gcc-6acf25e4b380e5ad738ffe2830a71635bc5230d1.tar.bz2 | |
peel-1.c: New testcase.
* gcc.dg/tree-prof/peel-1.c: New testcase.
* loop-unroll.c (decide_peel_simple): Simple peeling makes sense even
with simple loops; bound number of branches only when FDO is not
available.
(decide_unroll_stupid): Mention that num_loop_branches heuristics
is off.
From-SVN: r192718
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) |