[PATCH] Fix PR c++/14755
Jakub Jelinek
jakub@redhat.com
Wed Mar 31 18:39:00 GMT 2004
Hi!
This bug marked as critical has been introduced by the
2004-03-08 Roger Sayle <roger@eyesopen.com>
* fold-const.c (fold) <EQ_EXPR>: Rewrite optimization to transform
"foo++ == const" into "++foo == const+incr".
The masking is only correct for TREE_UNSIGNED (TREE_TYPE (varop)), otherwise
it needs sign extension to the bit fields precision.
Fixed thusly, ok to commit if bootstrap/regression testing succeeds?
Ok for 3.4/3.3 as well?
2004-03-31 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.
* gcc.c-torture/execute/20040331-1.c: New test.
* gcc.dg/20040331-1.c: New test.
--- gcc/fold-const.c.jj 2004-03-27 09:48:10.000000000 +0100
+++ gcc/fold-const.c 2004-03-31 20:29:51.209894745 +0200
@@ -7254,12 +7254,11 @@ 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
@@ -7271,25 +7270,12 @@ 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 (build (BIT_AND_EXPR, TREE_TYPE (varop),
- newconst, mask));
- }
+ shift = build_int_2 (TYPE_PRECISION (TREE_TYPE (varop)) - size,
+ 0);
+ newconst = fold (build (LSHIFT_EXPR, TREE_TYPE (varop),
+ newconst, shift));
+ newconst = fold (build (RSHIFT_EXPR, TREE_TYPE (varop),
+ newconst, shift));
}
return fold (build (code, type, varop, newconst));
--- gcc/testsuite/gcc.c-torture/execute/20040331-1.c.jj 2004-01-21 17:12:41.000000000 +0100
+++ gcc/testsuite/gcc.c-torture/execute/20040331-1.c 2004-03-31 19:00:39.244036708 +0200
@@ -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);
+}
--- gcc/testsuite/gcc.dg/20040331-1.c.jj 2004-01-21 17:12:41.000000000 +0100
+++ gcc/testsuite/gcc.dg/20040331-1.c 2004-03-31 19:31:59.405087369 +0200
@@ -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);
+}
Jakub
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