[Bug middle-end/19857] [4.0 Regression] alignment check of SSE constant fails in simple test program

jakub at gcc dot gnu dot org gcc-bugzilla@gcc.gnu.org
Thu Feb 10 21:11:00 GMT 2005


------- 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



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