openwrt/toolchain/gcc/3.4.4/900-integer_overflow.patch

   1 --- gcc.old/gcc/simplify-rtx.c  2005-03-23 15:41:59.000000000 +0100
   2 +++ gcc.dev/gcc/simplify-rtx.c  2007-01-30 11:42:38.407017680 +0100
   3 @@ -2607,18 +2607,18 @@
   4       a register or a CONST_INT, this can't help; testing for these cases will
   5       prevent infinite recursion here and speed things up.
   6
   7 -     If CODE is an unsigned comparison, then we can never do this optimization,
   8 -     because it gives an incorrect result if the subtraction wraps around zero.
   9 -     ANSI C defines unsigned operations such that they never overflow, and
  10 -     thus such cases can not be ignored.  */
  11 +     We can only do this for EQ and NE comparisons as otherwise we may
  12 +     lose or introduce overflow which we cannot disregard as undefined as
  13 +     we do not know the signedness of the operation on either the left or
  14 +     the right hand side of the comparison.  */
  15
  16    if (INTEGRAL_MODE_P (mode) && trueop1 != const0_rtx
  17 +      && (code == EQ || code == NE)
  18        && ! ((GET_CODE (op0) == REG || GET_CODE (trueop0) == CONST_INT)
  19             && (GET_CODE (op1) == REG || GET_CODE (trueop1) == CONST_INT))
  20        && 0 != (tem = simplify_binary_operation (MINUS, mode, op0, op1))
  21 -      /* We cannot do this for == or != if tem is a nonzero address.  */
  22 -      && ((code != EQ && code != NE) || ! nonzero_address_p (tem))
  23 -      && code != GTU && code != GEU && code != LTU && code != LEU)
  24 +      /* We cannot do this if tem is a nonzero address.  */
  25 +      && ! nonzero_address_p (tem))
  26      return simplify_relational_operation (signed_condition (code),
  27                                           mode, tem, const0_rtx);
  28