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re PR c++/14755 (miscompilation in bitfielded signed integers)

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PR c++/14755
	* fold-const.c (fold) <EQ_EXPR>: Properly compute newconst in
	"bitfld++ == const" to "++bitfld == const + incr" transformations.

	* gcc.c-torture/execute/20040331-1.c: New test.
	* gcc.dg/20040331-1.c: New test.

From-SVN: r80294
This commit is contained in:
Jakub Jelinek 2004-04-01 17:50:11 +02:00 committed by Jakub Jelinek
parent a150de2951
commit 0b61218593
5 changed files with 46 additions and 22 deletions
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6
gcc/ChangeLog
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@ -1,3 +1,9 @@
2004-04-01 Jakub Jelinek <jakub@redhat.com>
PR c++/14755
* fold-const.c (fold) <EQ_EXPR>: Properly compute newconst in
"bitfld++ == const" to "++bitfld == const + incr" transformations.
2004-04-01 Richard Kenner <kenner@vlsi1.ultra.nyu.edu>
* expr.c (get_inner_reference): Use DECL_UNSIGNED, not TREE_UNSIGNED.

30
gcc/fold-const.c
View File

@ -7338,12 +7338,11 @@ fold (tree expr)
/* If VAROP is a reference to a bitfield, we must mask
the constant by the width of the field. */
if (TREE_CODE (TREE_OPERAND (varop, 0)) == COMPONENT_REF
&& DECL_BIT_FIELD(TREE_OPERAND (TREE_OPERAND (varop, 0), 1)))
&& DECL_BIT_FIELD (TREE_OPERAND (TREE_OPERAND (varop, 0), 1)))
{
tree fielddecl = TREE_OPERAND (TREE_OPERAND (varop, 0), 1);
int size = TREE_INT_CST_LOW (DECL_SIZE (fielddecl));
tree folded_compare;
tree mask = 0;
tree folded_compare, shift;
/* First check whether the comparison would come out
always the same. If we don't do that we would
@ -7355,25 +7354,12 @@ fold (tree expr)
|| integer_onep (folded_compare))
return omit_one_operand (type, folded_compare, varop);
if (size < HOST_BITS_PER_WIDE_INT)
{
unsigned HOST_WIDE_INT lo = ((unsigned HOST_WIDE_INT) 1
<< size) - 1;
mask = build_int_2 (lo, 0);
}
else if (size < 2 * HOST_BITS_PER_WIDE_INT)
{
HOST_WIDE_INT hi = ((HOST_WIDE_INT) 1
<< (size - HOST_BITS_PER_WIDE_INT)) - 1;
mask = build_int_2 (~0, hi);
}
if (mask)
{
mask = fold_convert (TREE_TYPE (varop), mask);
newconst = fold (build2 (BIT_AND_EXPR, TREE_TYPE (varop),
newconst, mask));
}
shift = build_int_2 (TYPE_PRECISION (TREE_TYPE (varop)) - size,
0);
newconst = fold (build2 (LSHIFT_EXPR, TREE_TYPE (varop),
newconst, shift));
newconst = fold (build2 (RSHIFT_EXPR, TREE_TYPE (varop),
newconst, shift));
}
return fold (build2 (code, type, varop, newconst));

6
gcc/testsuite/ChangeLog
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@ -1,3 +1,9 @@
2004-04-01 Jakub Jelinek <jakub@redhat.com>
PR c++/14755
* gcc.c-torture/execute/20040331-1.c: New test.
* gcc.dg/20040331-1.c: New test.
2004-04-01 Paul Brook <paul@codesourcery.com>
* gcc.dg/arm-mmx-1.c: Add -mabi=iwmmxt to dg-options.

12
gcc/testsuite/gcc.c-torture/execute/20040331-1.c Normal file
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@ -0,0 +1,12 @@
/* PR c++/14755 */
extern void abort (void);
extern void exit (int);
int
main (void)
{
struct { int count: 31; } s = { 0 };
while (s.count--)
abort ();
exit (0);
}

14
gcc/testsuite/gcc.dg/20040331-1.c Normal file
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@ -0,0 +1,14 @@
/* { dg-do run } */
/* { dg-options "-O2 -fwrapv" } */
extern void abort (void);
extern void exit (int);
int
main (void)
{
struct { int count: 2; } s = { -2 };
while (s.count-- != -2)
abort ();
exit (0);
}