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From: "rguenth at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/33779] [4.3 Regression] folds unsigned multiplication == 0 to true
Date: Sat, 27 Oct 2007 17:29:00 -0000 [thread overview]
Message-ID: <20071027172925.1974.qmail@sourceware.org> (raw)
In-Reply-To: <bug-33779-10053@http.gcc.gnu.org/bugzilla/>
------- Comment #6 from rguenth at gcc dot gnu dot org 2007-10-27 17:29 -------
"This goes wrong in extract_muldiv..."
sorry for not pasting my complete analysis (actually the testcase is carefuly
crafted from looking at this code ;)). The recursion through conversions
case CONVERT_EXPR: case NON_LVALUE_EXPR: case NOP_EXPR:
/* If op0 is an expression ... */
if ((COMPARISON_CLASS_P (op0)
|| UNARY_CLASS_P (op0)
|| BINARY_CLASS_P (op0)
|| VL_EXP_CLASS_P (op0)
|| EXPRESSION_CLASS_P (op0))
/* ... and is unsigned, and its type is smaller than ctype,
then we cannot pass through as widening. */
&& ((TYPE_UNSIGNED (TREE_TYPE (op0))
&& ! (TREE_CODE (TREE_TYPE (op0)) == INTEGER_TYPE
&& TYPE_IS_SIZETYPE (TREE_TYPE (op0)))
&& (GET_MODE_SIZE (TYPE_MODE (ctype))
> GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (op0)))))
/* ... or this is a truncation (t is narrower than op0),
then we cannot pass through this narrowing. */
|| (GET_MODE_SIZE (TYPE_MODE (type))
< GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (op0))))
/* ... or signedness changes for division or modulus,
then we cannot pass through this conversion. */
|| (code != MULT_EXPR
&& (TYPE_UNSIGNED (ctype)
!= TYPE_UNSIGNED (TREE_TYPE (op0))))))
break;
/* Pass the constant down and see if we can make a simplification. If
we can, replace this expression with the inner simplification for
possible later conversion to our or some other type. */
if ((t2 = fold_convert (TREE_TYPE (op0), c)) != 0
&& TREE_CODE (t2) == INTEGER_CST
&& !TREE_OVERFLOW (t2)
&& (0 != (t1 = extract_muldiv (op0, t2, code,
code == MULT_EXPR
? ctype : NULL_TREE,
strict_overflow_p))))
return t1;
break;
is wrong as it might convert the transformation from one in unsigned type
to one in signed type.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33779
next prev parent reply other threads:[~2007-10-27 17:29 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-10-15 13:13 [Bug middle-end/33779] New: " rguenth at gcc dot gnu dot org
2007-10-15 13:24 ` [Bug middle-end/33779] " rguenth at gcc dot gnu dot org
2007-10-15 13:31 ` rguenth at gcc dot gnu dot org
2007-10-15 13:32 ` rguenth at gcc dot gnu dot org
2007-10-19 16:31 ` janis at gcc dot gnu dot org
2007-10-22 8:43 ` pinskia at gcc dot gnu dot org
2007-10-27 16:43 ` tromey at gcc dot gnu dot org
2007-10-27 17:29 ` rguenth at gcc dot gnu dot org [this message]
2007-10-27 17:30 ` rguenth at gcc dot gnu dot org
2007-10-31 12:33 ` rguenth at gcc dot gnu dot org
2007-10-31 12:34 ` rguenth at gcc dot gnu dot org
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