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tree-ssa-loop-niter.c (estimate_numbers_of_iterations_loop): Do not predict loops with multiple exits realistically.

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* tree-ssa-loop-niter.c (estimate_numbers_of_iterations_loop): Do not
	predict loops with multiple exits realistically.
	* cfgloopanal.c (single_likely_exit): New function.

	* gcc.dg/unroll_5.c: New testcase.

From-SVN: r192433
This commit is contained in:
Jan Hubicka 2012-10-14 18:18:26 +02:00 • committed by Jan Hubicka
parent ca6729e2ed
commit f9bf4777c1
5 changed files with 75 additions and 1 deletions
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6
gcc/ChangeLog
View file

@ -1,3 +1,9 @@
2012-10-14 Jan Hubicka <jh@suse.cz>
* tree-ssa-loop-niter.c (estimate_numbers_of_iterations_loop): Do not
predict loops with multiple exits realistically.
* cfgloopanal.c (single_likely_exit): New function.
2012-10-14 Uros Bizjak <ubizjak@gmail.com>
* config/alpha/alpha.md: Remove empty predicates and/or constraints.

37
gcc/cfgloopanal.c
View file

@ -446,3 +446,40 @@ mark_loop_exit_edges (void)
}
}
/* Return exit edge if loop has only one exit that is likely
to be executed on runtime (i.e. it is not EH or leading
to noreturn call. */
edge
single_likely_exit (struct loop *loop)
{
edge found = single_exit (loop);
VEC (edge, heap) *exits;
unsigned i;
edge ex;
if (found)
return found;
exits = get_loop_exit_edges (loop);
FOR_EACH_VEC_ELT (edge, exits, i, ex)
{
if (ex->flags & (EDGE_EH | EDGE_ABNORMAL_CALL))
continue;
/* The constant of 5 is set in a way so noreturn calls are
ruled out by this test. The static branch prediction algorithm
will not assign such a low probability to conditionals for usual
reasons. */
if (profile_status != PROFILE_ABSENT
&& ex->probability < 5 && !ex->count)
continue;
if (!found)
found = ex;
else
{
VEC_free (edge, heap, exits);
return NULL;
}
}
VEC_free (edge, heap, exits);
return found;
}

4
gcc/testsuite/ChangeLog
View file

@ -1,3 +1,7 @@
2012-10-14 Jan Hubicka <jh@suse.cz>
* gcc.dg/unroll_5.c: New testcase.
2012-10-14 Paolo Carlini <paolo.carlini@oracle.com>
PR c++/52643

25
gcc/testsuite/gcc.dg/unroll_5.c Normal file
View file

@ -0,0 +1,25 @@
/* { dg-do compile } */
/* { dg-options "-O3 -fdump-rtl-loop2_unroll -funroll-loops" } */
void abort (void);
int *a;
int t()
{
int i;
for (i=0;i<1000000;i++)
if (a[i])
return 1;
return 0;
}
int t2()
{
int i;
for (i=0;i<3000000;i++)
if (a[i])
abort ();
return 0;
}
/* { dg-final { scan-rtl-dump-times "upper bound: 999999" 1 "loop2_unroll" } } */
/* { dg-final { scan-rtl-dump-not "realistic bound: 999999" "loop2_unroll" } } */
/* { dg-final { scan-rtl-dump-times "upper bound: 2999999" 1 "loop2_unroll" } } */
/* { dg-final { scan-rtl-dump-times "realistic bound: 2999999" 1 "loop2_unroll" } } */
/* { dg-final { cleanup-rtl-dump "loop2_unroll" } } */

4
gcc/tree-ssa-loop-niter.c
View file

@ -2965,6 +2965,7 @@ estimate_numbers_of_iterations_loop (struct loop *loop)
struct tree_niter_desc niter_desc;
edge ex;
double_int bound;
edge likely_exit;
/* Give up if we already have tried to compute an estimation. */
if (loop->estimate_state != EST_NOT_COMPUTED)
@ -2975,6 +2976,7 @@ estimate_numbers_of_iterations_loop (struct loop *loop)
loop->any_estimate = false;
exits = get_loop_exit_edges (loop);
likely_exit = single_likely_exit (loop);
FOR_EACH_VEC_ELT (edge, exits, i, ex)
{
if (!number_of_iterations_exit (loop, ex, &niter_desc, false))
@ -2988,7 +2990,7 @@ estimate_numbers_of_iterations_loop (struct loop *loop)
niter);
record_estimate (loop, niter, niter_desc.max,
last_stmt (ex->src),
true, true, true);
true, ex == likely_exit, true);
}
VEC_free (edge, heap, exits);