* [Bug libc/5268] huge and denornal reads and writes for long doubles
[not found] <bug-5268-131@http.sourceware.org/bugzilla/>
@ 2012-02-21 1:28 ` jsm28 at gcc dot gnu.org
2013-06-26 2:53 ` amodra at gmail dot com
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From: jsm28 at gcc dot gnu.org @ 2012-02-21 1:28 UTC (permalink / raw)
To: glibc-bugs
http://sourceware.org/bugzilla/show_bug.cgi?id=5268
--- Comment #2 from Joseph Myers <jsm28 at gcc dot gnu.org> 2012-02-21 01:24:10 UTC ---
Ryan, ping. You said in 2008 you'd look at this....
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2012-02-21 1:28 ` [Bug libc/5268] huge and denornal reads and writes for long doubles jsm28 at gcc dot gnu.org
@ 2013-06-26 2:53 ` amodra at gmail dot com
2013-06-26 13:28 ` amodra at gmail dot com
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From: amodra at gmail dot com @ 2013-06-26 2:53 UTC (permalink / raw)
To: glibc-bugs
http://sourceware.org/bugzilla/show_bug.cgi?id=5268
Alan Modra <amodra at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |amodra at gmail dot com
--- Comment #3 from Alan Modra <amodra at gmail dot com> ---
huge() seems to give a long double having component doubles of 0x1p+1023
-0x1p+917. I'm not sure why this value is chosen, as it's quite a lot smaller
than the largest correctly rounded long double not an infinity. It's even
smaller than the value returned by huge() for double! And it's really really
odd that the low double is negative..
The actual maximum is 0x1.fffffffffffff7ffffffffffffcp+1023 (component doubles
of 0x1.fffffffffffffp+1023 0x1.fffffffffffffp+969). That "7" is there because
anything higher will cause the high double to be rounded to inf.
As to the bug with writing out the current huge() and reading back in, I think
you'll find the problem is related to normalisation in
sysdeps/ieee754/ldbl-128ibm/ldbl2mpn.c where the mantissa is trimmed to 105
bits. The current huge() has exponents that differ by 106. That means there
are 53 implicit bits of significand between the high double significand and the
low double significand.
So the number you're trying to write is actually
0x1.ffffffffffffffffffffffffff8p+1022 (if I can count) which ought to be OK.
However, ldbl2mpn.c normalises before subtracting, resulting in the low double
mantissa becoming zero. Net result is loss of one bit. This bug isn't
addressed by http://sourceware.org/ml/libc-alpha/2013-06/msg00919.html.
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2012-02-21 1:28 ` [Bug libc/5268] huge and denornal reads and writes for long doubles jsm28 at gcc dot gnu.org
2013-06-26 2:53 ` amodra at gmail dot com
@ 2013-06-26 13:28 ` amodra at gmail dot com
2013-06-29 4:04 ` amodra at gmail dot com
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From: amodra at gmail dot com @ 2013-06-26 13:28 UTC (permalink / raw)
To: glibc-bugs
http://sourceware.org/bugzilla/show_bug.cgi?id=5268
--- Comment #4 from Alan Modra <amodra at gmail dot com> ---
Created attachment 7095
--> http://sourceware.org/bugzilla/attachment.cgi?id=7095&action=edit
ldbl2mpn.c rewrite
This rewrite of __mpn_extract_long_double uses extra precision for the
normalization after subtraction, avoiding the loss of 1 bit.
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From: amodra at gmail dot com @ 2013-06-29 4:04 UTC (permalink / raw)
To: glibc-bugs
http://sourceware.org/bugzilla/show_bug.cgi?id=5268
--- Comment #5 from Alan Modra <amodra at gmail dot com> ---
> huge() seems to give a long double having component doubles of 0x1p+1023
> -0x1p+917. I'm not sure why this value is chosen
Ah, I knew I had something to do with this long double choice but had forgotten
the exact reason. See http://gcc.gnu.org/ml/fortran/2005-09/msg00556.html.
huge() has nothing to do with the maximum value for a machine representable
number.
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From: amodra at gmail dot com @ 2013-10-05 3:12 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=5268
Alan Modra <amodra at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
URL| |http://sourceware.org/ml/li
| |bc-alpha/2013-08/msg00106.h
| |tml
Assignee|rsa at us dot ibm.com |amodra at gmail dot com
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@ 2013-11-16 3:54 ` cvs-commit at gcc dot gnu.org
2014-02-07 2:33 ` [Bug libc/5268] [ldbl-128ibm] " jsm28 at gcc dot gnu.org
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From: cvs-commit at gcc dot gnu.org @ 2013-11-16 3:54 UTC (permalink / raw)
To: glibc-bugs
http://sourceware.org/bugzilla/show_bug.cgi?id=5268
--- Comment #6 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
This is an automated email from the git hooks/post-receive script. It was
generated because a ref change was pushed to the repository containing
the project "GNU C Library master sources".
The branch, ibm_2.18 has been created
at 40e9bbdd3d2ea22c2455949959ced90e054f6023 (commit)
- Log -----------------------------------------------------------------
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=40e9bbdd3d2ea22c2455949959ced90e054f6023
commit 40e9bbdd3d2ea22c2455949959ced90e054f6023
Author: Alan Modra <amodra@gmail.com>
Date: Sat Nov 16 10:18:28 2013 +1030
Mention powerpc64le support in NEWS and README, plus bugs fixed.
* NEWS: Mention powerpc64le support and bugs fixed.
* README: Both big-endian and little-endian powerpc64 supported.
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=74af96bf910f7e10289c72a397564dab19131b31
commit 74af96bf910f7e10289c72a397564dab19131b31
Author: Alan Modra <amodra@gmail.com>
Date: Sat Nov 16 10:09:06 2013 +1030
PowerPC64le has ifunc too.
I believe this is really just a "documentation" fix.
See https://sourceware.org/ml/binutils/2013-10/msg00059.html
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=d5f593430c7748f64321ecac36162646420a6aaf
commit d5f593430c7748f64321ecac36162646420a6aaf
Author: Alan Modra <amodra@gmail.com>
Date: Sat Oct 5 17:05:54 2013 +0930
Set arch_minimum_kernel for powerpc*le.
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=c325a11f7fa409423514de4af55ba63cc559cbf0
commit c325a11f7fa409423514de4af55ba63cc559cbf0
Author: Alan Modra <amodra@gmail.com>
Date: Sat Aug 17 19:11:11 2013 +0930
A little more precise %Lf for IBM long double
http://sourceware.org/ml/libc-alpha/2013-08/msg00106.html
IBM long double has variable precision and we often have values with
107 bits during the normal course of calculations. It's possible to
have an IBM long double with 2k bits of precision, and while some might
argue we ought to print to the full precision, I'm not inclined to try
to implement that.
So this patch gives the mpn values returned from ldbl2mpn() an extra
11 bits of precision. To do that it's necessary to inform the caller
of __mpn_extract_long_double() exactly how many bits are returned
rather than assuming a fixed LDBL_MANT_DIG bits. I did that
indirectly by returning the number of zero bits in the last mp_limb,
which turns out to be convenient both in __mpn_extract_long_double(),
and it's caller. Given the extra parameter it then becomes possible
to omit shifting in __mpn_extract_long_double(), since the caller does
that anyway.
In the following, note that 1 - IEEE854_LONG_DOUBLE_BIAS is equal to
LDBL_MIN_EXP - 1. I prefer the former since we already use
IEEE854_LONG_DOUBLE_BIAS in the exponent calculation for normalised
values, and it reinforces the fact that denormals are treated as if
their unbiased exponent was 1.
[BZ #5268]
* include/gmp.h (__mpn_extract_double, __mpn_extract_long_double):
Update prototypes.
* stdio-common/printf_fp.c: Likewise.
(__printf_fp): Use returned zero_bits.
* stdlib/dbl2mpn.c (__mpn_extract_double): Update funtion arguments.
* sysdeps/i386/ldbl2mpn.c (__mpn_extract_long_double): Don't perform
shifts for denormals here. Instead return leading zero bit count
and adjust return value of function.
* sysdeps/ieee754/dbl-64/dbl2mpn.c (__mpn_extract_long_double):
Likewise.
* sysdeps/ieee754/ldbl-128/ldbl2mpn.c (__mpn_extract_long_double):
Likewise.
* sysdeps/ieee754/ldbl-96/ldbl2mpn.c (__mpn_extract_long_double):
Likewise.
* sysdeps/ieee754/ldbl-128ibm/ldbl2mpn.c (__mpn_extract_long_double):
Likewise. Return an extra 11 bits of precision.
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=e24fc3c2914e0e17836455991e43151d453eb34c
commit e24fc3c2914e0e17836455991e43151d453eb34c
Author: Alan Modra <amodra@gmail.com>
Date: Thu Oct 3 14:09:27 2013 +0930
PowerPC LE ABI tests
http://sourceware.org/ml/libc-alpha/2013-08/msg00096.html
This adds ABI tests for powerpc64le.
* Makerules (abilist): Define and use var in abilist rules.
* sysdeps/unix/sysv/linux/powerpc/Makefile (abilist): Define.
* sysdeps/unix/sysv/linux/powerpc/powerpc64/nptl/ld-le.abilist,
*
sysdeps/unix/sysv/linux/powerpc/powerpc64/nptl/libBrokenLocale-le.abilist,
* sysdeps/unix/sysv/linux/powerpc/powerpc64/nptl/libanl-le.abilist,
* sysdeps/unix/sysv/linux/powerpc/powerpc64/nptl/libc-le.abilist,
* sysdeps/unix/sysv/linux/powerpc/powerpc64/nptl/libcrypt-le.abilist,
* sysdeps/unix/sysv/linux/powerpc/powerpc64/nptl/libdl-le.abilist,
* sysdeps/unix/sysv/linux/powerpc/powerpc64/nptl/libm-le.abilist,
* sysdeps/unix/sysv/linux/powerpc/powerpc64/nptl/libnsl-le.abilist,
* sysdeps/unix/sysv/linux/powerpc/powerpc64/nptl/libpthread-le.abilist,
* sysdeps/unix/sysv/linux/powerpc/powerpc64/nptl/libresolv-le.abilist,
* sysdeps/unix/sysv/linux/powerpc/powerpc64/nptl/librt-le.abilist,
*
sysdeps/unix/sysv/linux/powerpc/powerpc64/nptl/libthread_db-le.abilist,
* sysdeps/unix/sysv/linux/powerpc/powerpc64/nptl/libutil-le.abilist:
New files.
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@ 2014-02-07 2:33 ` jsm28 at gcc dot gnu.org
2014-07-14 14:51 ` carlos at redhat dot com
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From: jsm28 at gcc dot gnu.org @ 2014-02-07 2:33 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=5268
Joseph Myers <jsm28 at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|huge and denornal reads and |[ldbl-128ibm] huge and
|writes for long doubles |denornal reads and writes
| |for long doubles
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2014-02-07 2:33 ` [Bug libc/5268] [ldbl-128ibm] " jsm28 at gcc dot gnu.org
@ 2014-07-14 14:51 ` carlos at redhat dot com
2014-07-15 0:46 ` amodra at gmail dot com
2015-08-27 22:03 ` [Bug math/5268] " jsm28 at gcc dot gnu.org
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From: carlos at redhat dot com @ 2014-07-14 14:51 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=5268
Carlos O'Donell <carlos at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |carlos at redhat dot com
--- Comment #7 from Carlos O'Donell <carlos at redhat dot com> ---
Alan,
Is this fixed now?
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@ 2014-07-15 0:46 ` amodra at gmail dot com
2015-08-27 22:03 ` [Bug math/5268] " jsm28 at gcc dot gnu.org
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From: amodra at gmail dot com @ 2014-07-15 0:46 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=5268
--- Comment #8 from Alan Modra <amodra at gmail dot com> ---
No, the bug is not fixed, and I moved on to other things.
http://sourceware.org/ml/libc-alpha/2013-08/msg00106.html was never reviewed.
The commits here are for the ibm-2.18 branch..
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@ 2015-08-27 22:03 ` jsm28 at gcc dot gnu.org
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From: jsm28 at gcc dot gnu.org @ 2015-08-27 22:03 UTC (permalink / raw)
To: glibc-bugs
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Joseph Myers <jsm28 at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|libc |math
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