------- Comment #18 from tg at mirbsd dot org 2007-01-25 16:09 -------
Subject: Integer Overflow detection code optimised away, -fwrapv
broken
Dixi:
>Commit ID: 10045B8CAF141886704
>CVSROOT: /cvs
>Module name: gcc
>Changes by: [EMAIL PROTECTED] 2007/01/25 15:21:11 UTC
>
>Modified files:
> gcc : simplify-rtx.c
>
>Log message:
> ------- Comment [100]#17 From [101]Richard Guenther 2007-01-25 14:49 -------
>Backporting the fix for [102]PR28651 should fix it I guess.
Yes it does, thanks.
>To generate a diff of this changeset, execute the following commands:
>cvs -R rdiff -ur1.5 -r1.6 gcc/gcc/simplify-rtx.c
That is:
----- cutting here may damage your screen surface -----
Index: gcc/gcc/simplify-rtx.c
diff -u gcc/gcc/simplify-rtx.c:1.5 gcc/gcc/simplify-rtx.c:1.6
--- gcc/gcc/simplify-rtx.c:1.5 Thu Mar 30 19:50:29 2006
+++ gcc/gcc/simplify-rtx.c Thu Jan 25 15:21:10 2007
@@ -2686,18 +2686,18 @@
a register or a CONST_INT, this can't help; testing for these cases will
prevent infinite recursion here and speed things up.
- If CODE is an unsigned comparison, then we can never do this
optimization,
- because it gives an incorrect result if the subtraction wraps around
zero.
- ANSI C defines unsigned operations such that they never overflow, and
- thus such cases can not be ignored. */
+ We can only do this for EQ and NE comparisons as otherwise we may
+ lose or introduce overflow which we cannot disregard as undefined as
+ we do not know the signedness of the operation on either the left or
+ the right hand side of the comparison. */
if (INTEGRAL_MODE_P (mode) && trueop1 != const0_rtx
+ && (code == EQ || code == NE)
&& ! ((GET_CODE (op0) == REG || GET_CODE (trueop0) == CONST_INT)
&& (GET_CODE (op1) == REG || GET_CODE (trueop1) == CONST_INT))
&& 0 != (tem = simplify_binary_operation (MINUS, mode, op0, op1))
- /* We cannot do this for == or != if tem is a nonzero address. */
- && ((code != EQ && code != NE) || ! nonzero_address_p (tem))
- && code != GTU && code != GEU && code != LTU && code != LEU)
+ /* We cannot do this if tem is a nonzero address. */
+ && ! nonzero_address_p (tem))
return simplify_relational_operation (signed_condition (code),
mode, tem, const0_rtx);
----- cutting here may damage your screen surface -----
This applies to gcc 3.4.6 - if you need other versions, YMMV.
bye,
//mirabile
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30477
