Your message dated Mon, 18 Apr 2016 18:43:10 +0000
with message-id <e1ase8c-0005cb...@franck.debian.org>
and subject line Bug#821336: Removed package(s) from unstable
has caused the Debian Bug report #750834,
regarding gcc-4.8: [arm64] float to double conversion does not silence sNaN
to be marked as done.
This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
Bug report if necessary, and/or fix the problem forthwith.
(NB: If you are a system administrator and have no idea what this
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immediately.)
--
750834: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=750834
Debian Bug Tracking System
Contact ow...@bugs.debian.org with problems
--- Begin Message ---
Package: gcc-4.8
Version: 4.8.3-2
Severity: normal
Forwarded: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61441
Consider the following code:
#define _GNU_SOURCE
#include <stdio.h>
#include <math.h>
int main (void)
{
float sNaN = __builtin_nansf ("");
double x = (double) sNaN;
return issignaling(x);
}
It correctly returns 0 at -O0 optimisation level, but returns 1 at -O1
and -O2 optimisation levels.
Here is the generated assembly code at -O0:
0000000000400630 <main>:
400630: a9be7bfd stp x29, x30, [sp,#-32]!
400634: 910003fd mov x29, sp
400638: 18000160 ldr w0, 400664 <main+0x34>
40063c: b9001fa0 str w0, [x29,#28]
400640: b9401fa0 ldr w0, [x29,#28]
400644: 1e270000 fmov s0, w0
400648: 1e22c000 fcvt d0, s0
40064c: 9e660000 fmov x0, d0
400650: f9000ba0 str x0, [x29,#16]
400654: fd400ba0 ldr d0, [x29,#16]
400658: 97ffff8e bl 400490 <__issignaling@plt>
40065c: a8c27bfd ldp x29, x30, [sp],#32
400660: d65f03c0 ret
400664: 7fa00000 .word 0x7fa00000
Here is the generated assembly code at -O1:
0000000000400630 <main>:
400630: a9bf7bfd stp x29, x30, [sp,#-16]!
400634: 910003fd mov x29, sp
400638: 5c000080 ldr d0, 400648 <main+0x18>
40063c: 97ffff95 bl 400490 <__issignaling@plt>
400640: a8c17bfd ldp x29, x30, [sp],#16
400644: d65f03c0 ret
400648: 00000000 .word 0x00000000
40064c: 7ff40000 .word 0x7ff40000
As you can see at -O1, the sNaN constant is propagated, and the
propagated value is loaded and passed directly to issignaling.
Quoting the IEEE Std 754 standard:
"Under default exception handling, any operation signaling an invalid
operation exception and for which a floating-point result is to be
delivered shall deliver a quiet NaN."
So it looks like the copy propagation is not done correctly, the
sNaN should be silenced in the process.
Note: gcc-4.9 is also affected.
-- System Information:
Debian Release: jessie/sid
APT prefers unreleased
APT policy: (500, 'unreleased'), (500, 'unstable')
Architecture: arm64 (aarch64)
Kernel: Linux 3.15.0-5-generic (SMP w/1 CPU core)
Locale: LANG=fr_FR.UTF-8, LC_CTYPE=fr_FR.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Versions of packages gcc-4.8 depends on:
ii binutils 2.24.51.20140604-2
ii cpp-4.8 4.8.3-2
ii gcc-4.8-base 4.8.3-2
ii libc6 2.18-7
ii libcloog-isl4 0.18.2-1
ii libgcc-4.8-dev 4.8.3-2
ii libgmp10 2:6.0.0+dfsg-4
ii libisl10 0.12.2-1
ii libmpc3 1.0.1-1
ii libmpfr4 3.1.2-1
ii zlib1g 1:1.2.8.dfsg-1
Versions of packages gcc-4.8 recommends:
ii libc6-dev 2.18-7
Versions of packages gcc-4.8 suggests:
pn gcc-4.8-doc <none>
pn gcc-4.8-locales <none>
pn libasan0-dbg <none>
pn libatomic1-dbg <none>
pn libbacktrace1-dbg <none>
pn libgcc1-dbg <none>
pn libgomp1-dbg <none>
pn libitm1-dbg <none>
pn libquadmath-dbg <none>
pn libtsan0-dbg <none>
-- no debconf information
--- End Message ---
--- Begin Message ---
Version: 4.8.5-4+rm
Dear submitter,
as the package gcc-4.8 has just been removed from the Debian archive
unstable we hereby close the associated bug reports. We are sorry
that we couldn't deal with your issue properly.
For details on the removal, please see https://bugs.debian.org/821336
The version of this package that was in Debian prior to this removal
can still be found using http://snapshot.debian.org/.
This message was generated automatically; if you believe that there is
a problem with it please contact the archive administrators by mailing
ftpmas...@ftp-master.debian.org.
Debian distribution maintenance software
pp.
Scott Kitterman (the ftpmaster behind the curtain)
--- End Message ---