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re PR c++/34459 (incorrect code when compiled with optimization (-O1))

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PR c++/34459
	* tree-ssa-dse.c (dse_optimize_stmt): Don't eliminate store if
	USE_STMT not only stores into the same object as STMT, but might
	read it too.

	* gcc.c-torture/execute/20071219-1.c: New test.

From-SVN: r131101
This commit is contained in:
Jakub Jelinek 2007-12-20 15:40:33 +01:00 committed by Jakub Jelinek
parent 667e20459d
commit 3ec1a7379f
4 changed files with 103 additions and 0 deletions
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7
gcc/ChangeLog
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@ -1,3 +1,10 @@
2007-12-20 Jakub Jelinek <jakub@redhat.com>
PR c++/34459
* tree-ssa-dse.c (dse_optimize_stmt): Don't eliminate store if
USE_STMT not only stores into the same object as STMT, but might
read it too.
2007-12-19 Sebastian Pop <sebastian.pop@amd.com>
PR tree-optimization/34413

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2007-12-20 Jakub Jelinek <jakub@redhat.com>
PR c++/34459
* gcc.c-torture/execute/20071219-1.c: New test.
2007-12-20 Tobias Burnus <burnus@net-b.de>
PR fortran/34530

71
gcc/testsuite/gcc.c-torture/execute/20071219-1.c Normal file
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@ -0,0 +1,71 @@
/* PR c++/34459 */
extern void abort (void);
extern void *memset (void *s, int c, __SIZE_TYPE__ n);
struct S
{
char s[25];
};
struct S *p;
void __attribute__((noinline))
foo (struct S *x, int set)
{
int i;
for (i = 0; i < sizeof (x->s); ++i)
if (x->s[i] != 0)
abort ();
else if (set)
x->s[i] = set;
p = x;
}
void __attribute__((noinline))
test1 (void)
{
struct S a;
memset (&a.s, '\0', sizeof (a.s));
foo (&a, 0);
struct S b = a;
foo (&b, 1);
b = a;
b = b;
foo (&b, 0);
}
void __attribute__((noinline))
test2 (void)
{
struct S a;
memset (&a.s, '\0', sizeof (a.s));
foo (&a, 0);
struct S b = a;
foo (&b, 1);
b = a;
b = *p;
foo (&b, 0);
}
void __attribute__((noinline))
test3 (void)
{
struct S a;
memset (&a.s, '\0', sizeof (a.s));
foo (&a, 0);
struct S b = a;
foo (&b, 1);
*p = a;
*p = b;
foo (&b, 0);
}
int
main (void)
{
test1 ();
test2 ();
test3 ();
return 0;
}

20
gcc/tree-ssa-dse.c
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@ -470,6 +470,26 @@ dse_optimize_stmt (struct dom_walk_data *walk_data,
vuse_vec_p vv;
tree stmt_lhs;
if (LOADED_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;
}
}
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, " Deleted dead store '");