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author | Jan Hubicka <hubicka@gcc.gnu.org> | 2012-10-23 15:15:58 +0000 |
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committer | Jan Hubicka <hubicka@gcc.gnu.org> | 2012-10-23 15:15:58 +0000 |
commit | 6acf25e4b380e5ad738ffe2830a71635bc5230d1 (patch) | |
tree | 0f15c07165dd8eb1e94225c4f167441e61fadd00 /gcc | |
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')
-rw-r--r-- | gcc/ChangeLog | 8 | ||||
-rw-r--r-- | gcc/loop-unroll.c | 28 | ||||
-rw-r--r-- | gcc/testsuite/ChangeLog | 6 | ||||
-rw-r--r-- | gcc/testsuite/gcc.dg/tree-prof/peel-1.c | 25 |
4 files changed, 51 insertions, 16 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index bbe8f84..41e004b 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,11 @@ +2012-10-23 Jan Hubicka <jh@suse.cz> + + * 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. + 2012-10-23 Nick Clifton <nickc@redhat.com> PR target/54660 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) diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 89a4579..ddfef97 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,7 +1,11 @@ +2012-10-23 Jan Hubicka <jh@suse.cz> + + * gcc.dg/tree-prof/peel-1.c: New testcase. + 2012-10-23 Dominique d'Humieres <dominiq@lps.ens.fr> PR gcc/52945 - * testsuite/gcc.dg/lto/pr52634_0.c: skip the test on Darwin. + * gcc.dg/lto/pr52634_0.c: skip the test on Darwin. 2012-10-23 Joseph Myers <joseph@codesourcery.com> diff --git a/gcc/testsuite/gcc.dg/tree-prof/peel-1.c b/gcc/testsuite/gcc.dg/tree-prof/peel-1.c new file mode 100644 index 0000000..baa601d --- /dev/null +++ b/gcc/testsuite/gcc.dg/tree-prof/peel-1.c @@ -0,0 +1,25 @@ +/* { dg-options "-O3 -fdump-rtl-loop2_unroll -fno-unroll-loops -fpeel-loops" } */ +void abort(); + +int a[1000]; +int +__attribute__ ((noinline)) +t() +{ + int i; + for (i=0;i<1000;i++) + if (!a[i]) + return 1; + abort (); +} +main() +{ + int i; + for (i=0;i<1000;i++) + t(); + return 0; +} +/* { dg-final-use { scan-rtl-dump "Considering simply peeling loop" "loop2_unroll" } } */ +/* In fact one peeling is enough; we however mispredict number of iterations of the loop + at least until loop_ch is schedule ahead of profiling pass. */ +/* { dg-final-use { cleanup-rtl-dump "Decided to simply peel the loop 2 times" } } */ |