Date: Tue, 19 Aug 2003 23:24:46 +0200 (CEST) From: Mark Kettenis <kettenis@gnu.org> To: FreeBSD-gnats-submit@FreeBSD.org Subject: sparc64/55773: Conversion from long to long double is broken Message-ID: <200308192124.h7JLOknL002339@elgar.kettenis.dyndns.org> Resent-Message-ID: <200308200941.h7K9fqFE090746@freefall.freebsd.org>
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>Number: 55773
>Category: sparc64
>Synopsis: Conversion from long to long double is broken
>Confidential: no
>Severity: serious
>Priority: medium
>Responsible: freebsd-sparc64
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Wed Aug 20 02:41:50 PDT 2003
>Closed-Date:
>Last-Modified:
>Originator: Mark Kettenis
>Release: FreeBSD 5.1-CURRENT sparc64
>Organization:
>Environment:
System: FreeBSD panther.freebsd.org 5.1-CURRENT FreeBSD 5.1-CURRENT #166: Fri Aug 15 11:44:38 PDT 2003 root@panther.freebsd.org:/s/src/sys/sparc64/compile/PANTHER sparc64
>Description:
Conversion of `long' and `unsigned long' to `long double' are broken
on FreeBSD/sparc64. GCC generates the right code AFAICT, but the
implementation of _Qp_xtoq() and _Qp_uxtoq() in
/src/lib/libc/sparc64/fpu/fpu_qp.c seem to be broken. Every value
that has bit 32 set will be negative when converted to a `long
double'.
>How-To-Repeat:
The following test program exhibits the behaviour:
#include <stdio.h>
unsigned long mant_long = 0x80000000;
int
main (void)
{
long double mant = mant_long;
printf ("%lu\n", mant_long);
printf ("%Lf\n", mant);
return 0;
}
which should print
2147483648
2147483648.000000
but will print
2147483648
-2147483648.000000
>Fix:
Looking at the code in /usr/src/lib/libc/sparc64/fpu/fpu_qp.c (I'm
looking at revision 1.3), it seems that the _QP_TTOQ() macro only
handles 32-bit signed integers since on line 63 of that file we have:
fe.fe_f1.fp_sign = a[0] >> 31;
I think that this line should be
fe.fe_f1.fp_sign = a[0] >> 63;
for `long' (_Qp_xtoq) and that the line should be completely absent
for `unsigned' (_Qp_uitoq) and `unsigned long' (_Qp_uxtoq). Some
not-too-thorough testing seems to indicate that's right.
>Release-Note:
>Audit-Trail:
>Unformatted:
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