------- Comment #1 from rguenth at gcc dot gnu dot org 2006-12-27 16:48 -------
This is folded to
;; Function notneg (notneg)
;; enabled by -tree-original
{
return x != -2147483648;
}
;; Function negnot (negnot)
;; enabled by -tree-original
{
return x != 2147483647;
}
via
/* Convert - (~A) to A + 1. */
if (INTEGRAL_TYPE_P (type) && TREE_CODE (arg0) == BIT_NOT_EXPR)
return fold_build2 (PLUS_EXPR, type, TREE_OPERAND (arg0, 0),
build_int_cst (type, 1));
and
/* Convert ~ (-A) to A - 1. */
else if (INTEGRAL_TYPE_P (type) && TREE_CODE (arg0) == NEGATE_EXPR)
return fold_build2 (MINUS_EXPR, type, TREE_OPERAND (arg0, 0),
build_int_cst (type, 1));
and
/* Transform comparisons of the form X +- C1 CMP C2 to X CMP C2 +- C1.
*/ if ((TREE_CODE (arg0) == PLUS_EXPR || TREE_CODE (arg0) == MINUS_EXPR)
&& (TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST
&& !TREE_OVERFLOW (TREE_OPERAND (arg0, 1))
&& !TYPE_UNSIGNED (TREE_TYPE (arg1))
&& !(flag_wrapv || flag_trapv))
&& (TREE_CODE (arg1) == INTEGER_CST
&& !TREE_OVERFLOW (arg1)))
{
tree const1 = TREE_OPERAND (arg0, 1);
tree const2 = arg1;
tree variable = TREE_OPERAND (arg0, 0);
tree lhs;
int lhs_add;
lhs_add = TREE_CODE (arg0) != PLUS_EXPR;
lhs = fold_build2 (lhs_add ? PLUS_EXPR : MINUS_EXPR,
TREE_TYPE (arg1), const2, const1);
if (TREE_CODE (lhs) == TREE_CODE (arg1)
&& (TREE_CODE (lhs) != INTEGER_CST
|| !TREE_OVERFLOW (lhs)))
return fold_build2 (code, type, variable, lhs);
}
(citing from the 4.1 branch)
Note this is actually wrong-code.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |rguenth at gcc dot gnu dot
| |org
Status|UNCONFIRMED |NEW
Ever Confirmed|0 |1
Keywords| |wrong-code
Known to fail| |4.1.2 4.3.0
Known to work| |4.0.3
Last reconfirmed|0000-00-00 00:00:00 |2006-12-27 16:48:37
date| |
Summary|missed optimization due to |folding (~ -x) >= (-
|bad range propagation |2147483647-1) to x != -
|without -fwrapv |2147483648
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30267
