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re PR tree-optimization/57343 (wrong code on x86_64-linux at -Os and above) 

2013-05-27  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/57343
	* tree-ssa-loop-niter.c (number_of_iterations_ne_max): Do not
	use multiple_of_p if not TYPE_OVERFLOW_UNDEFINED.
	(number_of_iterations_cond): Do not build the folded tree.

	* gcc.dg/torture/pr57343.c: New testcase.

From-SVN: r199357
This commit is contained in:
Richard Biener 2013-05-27 13:02:24 +00:00 committed by Richard Biener
parent d1de852b68
commit 5a89224823
4 changed files with 48 additions and 6 deletions
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7
gcc/ChangeLog
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@ -1,3 +1,10 @@
2013-05-27 Richard Biener <rguenther@suse.de>
PR tree-optimization/57343
* tree-ssa-loop-niter.c (number_of_iterations_ne_max): Do not
use multiple_of_p if not TYPE_OVERFLOW_UNDEFINED.
(number_of_iterations_cond): Do not build the folded tree.
2013-05-27 Richard Biener <rguenther@suse.de>
Revert

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2013-05-27 Richard Biener <rguenther@suse.de>
PR tree-optimization/57343
* gcc.dg/torture/pr57343.c: New testcase.
2013-05-27 Richard Biener <rguenther@suse.de>
PR tree-optimization/57417

22
gcc/testsuite/gcc.dg/torture/pr57343.c Normal file
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@ -0,0 +1,22 @@
/* { dg-do run } */
int c = 0;
int
main ()
{
int i, f = 1;
for (i = 0; i < 5; i++)
{
--c;
unsigned char h = c * 100;
if (h == 0)
{
f = 0;
break;
}
}
if (f != 1)
__builtin_abort ();
return 0;
}

20
gcc/tree-ssa-loop-niter.c
View File

@ -552,10 +552,18 @@ number_of_iterations_ne_max (mpz_t bnd, bool no_overflow, tree c, tree s,
{
double_int max;
mpz_t d;
tree type = TREE_TYPE (c);
bool bnds_u_valid = ((no_overflow && exit_must_be_taken)
|| mpz_sgn (bnds->below) >= 0);
if (multiple_of_p (TREE_TYPE (c), c, s))
if (integer_onep (s)
|| (TREE_CODE (c) == INTEGER_CST
&& TREE_CODE (s) == INTEGER_CST
&& tree_to_double_int (c).mod (tree_to_double_int (s),
TYPE_UNSIGNED (type),
EXACT_DIV_EXPR).is_zero ())
|| (TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (c))
&& multiple_of_p (type, c, s)))
{
/* If C is an exact multiple of S, then its value will be reached before
the induction variable overflows (unless the loop is exited in some
@ -572,16 +580,15 @@ number_of_iterations_ne_max (mpz_t bnd, bool no_overflow, tree c, tree s,
the whole # of iterations analysis will fail). */
if (!no_overflow)
{
max = double_int::mask (TYPE_PRECISION (TREE_TYPE (c))
- tree_low_cst (num_ending_zeros (s), 1));
max = double_int::mask (TYPE_PRECISION (type)
- tree_low_cst (num_ending_zeros (s), 1));
mpz_set_double_int (bnd, max, true);
return;
}
/* Now we know that the induction variable does not overflow, so the loop
iterates at most (range of type / S) times. */
mpz_set_double_int (bnd, double_int::mask (TYPE_PRECISION (TREE_TYPE (c))),
true);
mpz_set_double_int (bnd, double_int::mask (TYPE_PRECISION (type)), true);
/* If the induction variable is guaranteed to reach the value of C before
overflow, ... */
@ -1311,7 +1318,8 @@ number_of_iterations_cond (struct loop *loop,
}
/* If the loop exits immediately, there is nothing to do. */
if (integer_zerop (fold_build2 (code, boolean_type_node, iv0->base, iv1->base)))
tree tem = fold_binary (code, boolean_type_node, iv0->base, iv1->base);
if (tem && integer_zerop (tem))
{
niter->niter = build_int_cst (unsigned_type_for (type), 0);
niter->max = double_int_zero;