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re PR middle-end/58941 (value modification on zero-length array optimized away)

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2013-11-05  Richard Biener  <rguenther@suse.de>

	PR middle-end/58941
	* tree-dfa.c (get_ref_base_and_extent): Merge common code
	in MEM_REF and TARGET_MEM_REF handling.  Make sure to
	process trailing array detection before diving into the
	view-converted object (and possibly apply some extra offset).

	* gcc.dg/torture/pr58941.c: New testcase.

From-SVN: r204391
This commit is contained in:
Richard Biener 2013-11-05 13:24:13 +00:00 • committed by Richard Biener
parent 254a0760a1
commit 4f94d87c61
4 changed files with 88 additions and 53 deletions
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8
gcc/ChangeLog
View file

@ -1,3 +1,11 @@
2013-11-05 Richard Biener <rguenther@suse.de>
PR middle-end/58941
* tree-dfa.c (get_ref_base_and_extent): Merge common code
in MEM_REF and TARGET_MEM_REF handling. Make sure to
process trailing array detection before diving into the
view-converted object (and possibly apply some extra offset).
2013-11-05 Joseph Myers <joseph@codesourcery.com>
* config/i386/i386.c (ix86_float_exceptions_rounding_supported_p):

5
gcc/testsuite/ChangeLog
View file

@ -1,3 +1,8 @@
2013-11-05 Richard Biener <rguenther@suse.de>
PR middle-end/58941
* gcc.dg/torture/pr58941.c: New testcase.
2013-11-05 Marc Glisse <marc.glisse@inria.fr>
PR tree-optimization/58958

33
gcc/testsuite/gcc.dg/torture/pr58941.c Normal file
View file

@ -0,0 +1,33 @@
/* { dg-do run } */
extern void abort (void);
typedef struct {
int msgLength;
unsigned char data[1000];
} SMsg;
typedef struct {
int dummy;
int d[0];
} SData;
int condition = 3;
int main()
{
SMsg msg;
SData *pData = (SData*)(msg.data);
unsigned int i = 0;
for (i = 0; i < 1; i++)
{
pData->d[i] = 0;
if(condition & 1)
pData->d[i] |= 0x55;
if(condition & 2)
pData->d[i] |= 0xaa;
}
if (pData->d[0] != 0xff)
abort ();
return 0;
}

95
gcc/tree-dfa.c
View file

@ -389,7 +389,6 @@ get_ref_base_and_extent (tree exp, HOST_WIDE_INT *poffset,
double_int bit_offset = double_int_zero;
HOST_WIDE_INT hbit_offset;
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)
@ -420,8 +419,6 @@ 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:
@ -544,42 +541,43 @@ get_ref_base_and_extent (tree exp, HOST_WIDE_INT *poffset,
case VIEW_CONVERT_EXPR:
break;
case TARGET_MEM_REF:
/* Via the variable index or index2 we can reach the
whole object. Still hand back the decl here. */
if (TREE_CODE (TMR_BASE (exp)) == ADDR_EXPR
&& (TMR_INDEX (exp) || TMR_INDEX2 (exp)))
{
exp = TREE_OPERAND (TMR_BASE (exp), 0);
bit_offset = double_int_zero;
maxsize = -1;
goto done;
}
/* Fallthru. */
case MEM_REF:
/* We need to deal with variable arrays ending structures such as
struct { int length; int a[1]; } x; x.a[d]
struct { struct { int a; int b; } a[1]; } x; x.a[d].a
struct { struct { int a[1]; } a[1]; } x; x.a[0][d], x.a[d][0]
struct { int len; union { int a[1]; struct X x; } u; } x; x.u.a[d]
where we do not know maxsize for variable index accesses to
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. */
if (seen_variable_array_ref
&& maxsize != -1
&& (!bit_offset.fits_shwi ()
|| !host_integerp (TYPE_SIZE (TREE_TYPE (exp)), 1)
|| (bit_offset.to_shwi () + maxsize
== (signed) TREE_INT_CST_LOW
(TYPE_SIZE (TREE_TYPE (exp))))))
maxsize = -1;
/* Hand back the decl for MEM[&decl, off]. */
if (TREE_CODE (TREE_OPERAND (exp, 0)) == ADDR_EXPR)
{
if (integer_zerop (TREE_OPERAND (exp, 1)))
exp = TREE_OPERAND (TREE_OPERAND (exp, 0), 0);
else
{
double_int off = mem_ref_offset (exp);
off = off.lshift (BITS_PER_UNIT == 8
? 3 : exact_log2 (BITS_PER_UNIT));
off = off + bit_offset;
if (off.fits_shwi ())
{
bit_offset = off;
exp = TREE_OPERAND (TREE_OPERAND (exp, 0), 0);
}
}
}
goto done;
case TARGET_MEM_REF:
/* Hand back the decl for MEM[&decl, off]. */
if (TREE_CODE (TMR_BASE (exp)) == ADDR_EXPR)
{
/* Via the variable index or index2 we can reach the
whole object. */
if (TMR_INDEX (exp) || TMR_INDEX2 (exp))
{
exp = TREE_OPERAND (TMR_BASE (exp), 0);
bit_offset = double_int_zero;
maxsize = -1;
goto done;
}
if (integer_zerop (TMR_OFFSET (exp)))
exp = TREE_OPERAND (TMR_BASE (exp), 0);
else
{
double_int off = mem_ref_offset (exp);
@ -589,7 +587,7 @@ get_ref_base_and_extent (tree exp, HOST_WIDE_INT *poffset,
if (off.fits_shwi ())
{
bit_offset = off;
exp = TREE_OPERAND (TMR_BASE (exp), 0);
exp = TREE_OPERAND (TREE_OPERAND (exp, 0), 0);
}
}
}
@ -601,8 +599,17 @@ get_ref_base_and_extent (tree exp, HOST_WIDE_INT *poffset,
exp = TREE_OPERAND (exp, 0);
}
done:
/* We need to deal with variable arrays ending structures. */
if (seen_variable_array_ref
&& maxsize != -1
&& (!bit_offset.fits_shwi ()
|| !host_integerp (TYPE_SIZE (TREE_TYPE (exp)), 1)
|| (bit_offset.to_shwi () + maxsize
== (signed) TREE_INT_CST_LOW (TYPE_SIZE (TREE_TYPE (exp))))))
maxsize = -1;
done:
if (!bit_offset.fits_shwi ())
{
*poffset = 0;
@ -614,24 +621,6 @@ get_ref_base_and_extent (tree exp, HOST_WIDE_INT *poffset,
hbit_offset = bit_offset.to_shwi ();
/* We need to deal with variable arrays ending structures such as
struct { int length; int a[1]; } x; x.a[d]
struct { struct { int a; int b; } a[1]; } x; x.a[d].a
struct { struct { int a[1]; } a[1]; } x; x.a[0][d], x.a[d][0]
struct { int len; union { int a[1]; struct X x; } u; } x; x.u.a[d]
where we do not know maxsize for variable index accesses to
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. */
if (seen_variable_array_ref
&& maxsize != -1
&& (!host_integerp (TYPE_SIZE (base_type), 1)
|| (hbit_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))