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re PR tree-optimization/35472 (tree DSE is broken)

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2008-03-05  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/35472
	* tree-ssa-dse.c (dse_optimize_stmt): Do not delete a store
	whose single use_stmt has a overlapping set of loaded and
	stored symbols as that use_stmt might be a noop assignment then.

	* gcc.c-torture/execute/pr35472.c: New testcase.

From-SVN: r132899
This commit is contained in:
Richard Guenther 2008-03-05 16:13:04 +00:00 • committed by Richard Biener
parent fec5fe47e6
commit 1bdcf037b3
4 changed files with 50 additions and 17 deletions
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7
gcc/ChangeLog
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@ -1,3 +1,10 @@
2008-03-05 Richard Guenther <rguenther@suse.de>
PR tree-optimization/35472
* tree-ssa-dse.c (dse_optimize_stmt): Do not delete a store
whose single use_stmt has a overlapping set of loaded and
stored symbols as that use_stmt might be a noop assignment then.
2008-03-05 Joel Sherrill <joel.sherrill@oarcorp.com>
* gthr-rtems.h: Implement __gthread_mutex_destroy.

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2008-03-05 Richard Guenther <rguenther@suse.de>
PR tree-optimization/35472
* gcc.c-torture/execute/pr35472.c: New testcase.
2007-03-05 Gabor Loki <loki@gcc.gnu.org>
PR 33009

22
gcc/testsuite/gcc.c-torture/execute/pr35472.c Normal file
View file

@ -0,0 +1,22 @@
extern void abort (void);
extern void *memset (void *s, int c, __SIZE_TYPE__ n);
struct S { int i[16]; };
struct S *p;
void __attribute__((noinline))
foo(struct S *a, struct S *b) { a->i[0] = -1; p = b; }
void test (void)
{
struct S a, b;
memset (&a.i[0], '\0', sizeof (a.i));
memset (&b.i[0], '\0', sizeof (b.i));
foo (&a, &b);
*p = a;
*p = b;
if (b.i[0] != -1)
abort ();
}
int main()
{
test();
return 0;
}

33
gcc/tree-ssa-dse.c
View file

@ -470,24 +470,23 @@ dse_optimize_stmt (struct dom_walk_data *walk_data,
vuse_vec_p vv;
tree stmt_lhs;
if (LOADED_SYMS (use_stmt))
/* If use_stmt is or might be a nop assignment, e.g. for
struct { ... } S a, b, *p; ...
b = a; b = b;
or
b = a; b = *p; where p might be &b,
or
*p = a; *p = b; where p might be &b,
or
*p = *u; *p = *v; where p might be v, then USE_STMT
acts as a use as well as definition, so store in STMT
is not dead. */
if (LOADED_SYMS (use_stmt)
&& bitmap_intersect_p (LOADED_SYMS (use_stmt),
STORED_SYMS (use_stmt)))
{
tree use_base
= get_base_address (GIMPLE_STMT_OPERAND (use_stmt, 0));
/* If use_stmt is or might be a nop assignment, e.g. for
struct { ... } S a, b, *p; ...
b = a; b = b;
or
b = a; b = *p; where p might be &b, then USE_STMT
acts as a use as well as definition, so store in STMT
is not dead. */
if (TREE_CODE (use_base) == VAR_DECL
&& bitmap_bit_p (LOADED_SYMS (use_stmt),
DECL_UID (use_base)))
{
record_voperand_set (dse_gd->stores, &bd->stores, ann->uid);
return;
}
record_voperand_set (dse_gd->stores, &bd->stores, ann->uid);
return;
}
if (dump_file && (dump_flags & TDF_DETAILS))