Date: Thu, 6 Dec 2012 12:17:53 -0500 (EST) From: Keith White <kwhite@uottawa.ca> To: FreeBSD-gnats-submit@FreeBSD.org Subject: bin/174240: bin/clang i386 generates incorrect code for ports/devel/dev86 Message-ID: <201212061717.qB6HHrNW004277@localhost.my.domain> Resent-Message-ID: <201212061750.qB6Ho0Nl055096@freefall.freebsd.org>
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>Number: 174240
>Category: bin
>Synopsis: bin/clang i386 generates incorrect code for ports/devel/dev86
>Confidential: no
>Severity: serious
>Priority: high
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Thu Dec 06 17:50:00 UTC 2012
>Closed-Date:
>Last-Modified:
>Originator: Keith White
>Release: FreeBSD 10.0-CURRENT amd64
>Organization:
SITE, University of Ottawa
>Environment:
System: FreeBSD freebsd10 10.0-CURRENT FreeBSD 10.0-CURRENT #10 r243890M: Wed Dec 5 11:39:25 EST 2012 root@freebsd10:/usr/obj/usr/src/sys/GENERIC amd64
>Description:
clang (i386) compiles ports/devel/dev86/.../as/genlist.c:build_number()
to an infinite loop when optimization -O2 is turned on.
>How-To-Repeat:
Extract build_number() from ports/devel/dev86/.../as/genlist.c
=== bn.c ===
PUBLIC char *build_number(num, width, where)
unsigned num;
unsigned width;
register char *where;
{
static unsigned powers_of_10[] = {1, 10, 100, 1000, 10000,};
unsigned char digit;
unsigned char power;
register unsigned power_of_10;
power = 5; /* actually 1 more than power */
do
{
for (digit = '0', power_of_10 = (powers_of_10 - 1)[power];
num >= power_of_10; num -= power_of_10)
++digit;
if (power <= width)
*where++ = digit;
}
while (--power != 0);
return where;
}
============
clang -m32 --version
FreeBSD clang version 3.2 (branches/release_32 168974) 20121130
Target: i386-unknown-freebsd10.0
Thread model: posix
clang -O2 -DPUBLIC="" -m32 -c -save-temps bn.c
cat bn.s
...
build_number: # @build_number
# BB#0: # %for.body.lr.ph
.align 16, 0x90
.LBB0_1: # %for.body
# =>This Inner Loop Header: Depth=1
jmp .LBB0_1
...
>Fix:
Fix to clang unknown.
clang generates correct code when "power" is made volatile.
==== devel/dev86 port patch ====
--- dev86-0.16.18/as/genlist.c.orig 2001-06-23 16:13:19.000000000 -0400
+++ dev86-0.16.18/as/genlist.c 2012-12-06 12:11:26.000000000 -0500
@@ -113,7 +113,7 @@
{
static unsigned powers_of_10[] = {1, 10, 100, 1000, 10000,};
unsigned char digit;
- unsigned char power;
+ volatile unsigned char power;
register unsigned power_of_10;
power = 5; /* actually 1 more than power */
====
...keith
>Release-Note:
>Audit-Trail:
>Unformatted:
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