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re PR tree-optimization/49079 (Bogus constant folding)

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2011-05-20  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/49079
	* tree-dfa.c (get_ref_base_and_extent): Handle view-converting
	MEM_REFs correctly for the trailing array access detection.
	Special case constants the same way as decls for overall size
	constraining.

	* gcc.dg/torture/pr49079.c: New testcase.

From-SVN: r173954
This commit is contained in:
Richard Guenther 2011-05-20 15:02:49 +00:00 committed by Richard Biener
parent 3cda91d863
commit 90ff582fb1
4 changed files with 64 additions and 8 deletions
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8
gcc/ChangeLog
View File

@ -1,3 +1,11 @@
2011-05-20 Richard Guenther <rguenther@suse.de>
PR tree-optimization/49079
* tree-dfa.c (get_ref_base_and_extent): Handle view-converting
MEM_REFs correctly for the trailing array access detection.
Special case constants the same way as decls for overall size
constraining.
2011-05-20 Uros Bizjak <ubizjak@gmail.com>
* config/i386/mingw32.h (OUTPUT_QUOTED_STRING): Fix macro

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2011-05-20 Richard Guenther <rguenther@suse.de>
PR tree-optimization/49079
* gcc.dg/torture/pr49079.c: New testcase.
2011-05-20 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/49073

31
gcc/testsuite/gcc.dg/torture/pr49079.c Normal file
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@ -0,0 +1,31 @@
/* { dg-do run } */
extern void abort (void);
struct Ustr
{
unsigned char data[1];
};
static unsigned int
ustr_xi__embed_val_get(const unsigned char *data)
{
return (unsigned int)data[0];
}
int __attribute__((noinline)) zero(void) { return 0; }
static unsigned int
ustr_len(const struct Ustr *s1)
{
return ustr_xi__embed_val_get(s1->data + 1 + zero());
}
int
main()
{
if (ustr_len (((struct Ustr *) "\x01" "\x0002" "s2")) != 2)
abort ();
return 0;
}

28
gcc/tree-dfa.c
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@ -714,6 +714,7 @@ get_ref_base_and_extent (tree exp, HOST_WIDE_INT *poffset,
tree size_tree = NULL_TREE;
HOST_WIDE_INT bit_offset = 0;
bool seen_variable_array_ref = false;
tree base_type;
/* First get the final access size from just the outermost expression. */
if (TREE_CODE (exp) == COMPONENT_REF)
@ -744,6 +745,8 @@ get_ref_base_and_extent (tree exp, HOST_WIDE_INT *poffset,
and find the ultimate containing object. */
while (1)
{
base_type = TREE_TYPE (exp);
switch (TREE_CODE (exp))
{
case BIT_FIELD_REF:
@ -931,9 +934,16 @@ get_ref_base_and_extent (tree exp, HOST_WIDE_INT *poffset,
the array. The simplest way to conservatively deal with this
is to punt in the case that offset + maxsize reaches the
base type boundary. This needs to include possible trailing padding
that is there for alignment purposes.
that is there for alignment purposes. */
That is of course only true if the base object is not a decl. */
if (seen_variable_array_ref
&& maxsize != -1
&& (!host_integerp (TYPE_SIZE (base_type), 1)
|| (bit_offset + maxsize
== (signed) TREE_INT_CST_LOW (TYPE_SIZE (base_type)))))
maxsize = -1;
/* In case of a decl or constant base object we can do better. */
if (DECL_P (exp))
{
@ -943,12 +953,14 @@ get_ref_base_and_extent (tree exp, HOST_WIDE_INT *poffset,
&& host_integerp (DECL_SIZE (exp), 1))
maxsize = TREE_INT_CST_LOW (DECL_SIZE (exp)) - bit_offset;
}
else if (seen_variable_array_ref
&& maxsize != -1
&& (!host_integerp (TYPE_SIZE (TREE_TYPE (exp)), 1)
|| (bit_offset + maxsize
== (signed) TREE_INT_CST_LOW (TYPE_SIZE (TREE_TYPE (exp))))))
maxsize = -1;
else if (CONSTANT_CLASS_P (exp))
{
/* If maxsize is unknown adjust it according to the size of the
base type constant. */
if (maxsize == -1
&& host_integerp (TYPE_SIZE (TREE_TYPE (exp)), 1))
maxsize = TREE_INT_CST_LOW (TYPE_SIZE (TREE_TYPE (exp))) - bit_offset;
}
/* ??? Due to negative offsets in ARRAY_REF we can end up with
negative bit_offset here. We might want to store a zero offset