------- Additional Comments From jakub at gcc dot gnu dot org 2005-02-10 18:07
-------
Actually, I see there multiple problems elsewhere.
First is on
int i;
int foo (void)
{
return i & ~(unsigned int)3;
}
First is that
if (change)
return fold (build2 (BIT_AND_EXPR, type,
fold_convert (type, and0),
fold_convert (type, and1)));
folds (int) ((unsigned)i & ~(unsigned)3) into i & (int)~(unsigned)3 where
(int)~(unsigned)3 is -4 with TREE_OVERFLOW set. But there is no overflow
in the original program, so we shouldn't IMHO create one as part of this
optimization.
Another problem is that
case POINTER_TYPE:
case REFERENCE_TYPE:
if (integer_zerop (expr))
expr = integer_zero_node;
else
expr = fold (build1 (CONVERT_EXPR,
lang_hooks.types.type_for_size (POINTER_SIZE, 0),
expr));
return convert_to_integer (type, expr);
unconditionally converts to signed type as wide as pointer (== intptr_t) instead
of considering TYPE_UNSIGNED (type).
As the result of these 2, fold_truthop is presented with ll_mask and ll_and_mask
TREE_OVERFLOW -4 and given that gets confused into believing the whole
comparison
is always 0.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19857
