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Bug 394271

Summary:	gcc optimization error for neg number * abs() [extract_muldiv]
Product:	Red Hat Enterprise Linux 4	Reporter:	Jan Iven <jan.iven>
Component:	gcc	Assignee:	Jakub Jelinek <jakub>
Status:	CLOSED ERRATA	QA Contact:
Severity:	high	Docs Contact:
Priority:	medium
Version:	4.0	CC:	k.georgiou, mnowak, pmuller, rdassen, riek, tao
Target Milestone:	---
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2009-05-18 20:33:43 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Jan Iven 2007-11-21 15:18:35 UTC

As reported on http://linux.solidot.org/article.pl?sid=07/11/19/0512218&from=rss
and http://lkml.org/lkml/2007/11/19/493, the following test program triggers 
an optimization bug in gcc for the builtin abs() function:

int main () {
                int i=2;
                if( -10*abs (i-1) == 10*abs(i-1) )
                                printf ("OMG,-10==10 in linux!\n");
                else
                                printf ("nothing special here\n");
}


Verified with RHEL4 (gcc-3.4.6-8), RHEL5 (gcc-4.1.2-14.el5), F8 (gcc-4.1.2-33).
Upstream patch at
http://www.nabble.com/-PATCH--Fix-PR34130,-extract_muldiv-broken-t4826688.html

Comment 2 RHEL Program Management 2008-09-05 17:21:26 UTC

This request was evaluated by Red Hat Product Management for inclusion in a Red
Hat Enterprise Linux maintenance release.  Product Management has requested
further review of this request by Red Hat Engineering, for potential
inclusion in a Red Hat Enterprise Linux Update release for currently deployed
products.  This request is not yet committed for inclusion in an Update
release.

Comment 3 Jakub Jelinek 2008-09-30 16:22:11 UTC

Already in gcc4-4.1.2-42.EL4 (and in RHEL5), will backport to gcc-3.4.6-RH too.

Comment 11 errata-xmlrpc 2009-05-18 20:33:43 UTC

An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

http://rhn.redhat.com/errata/RHBA-2009-1016.html