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[Bug math/16731] log(1) is -0, should be +0, in FE_DOWNWARD mode
- From: "cvs-commit at gcc dot gnu.org" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sourceware dot org
- Date: Fri, 21 Mar 2014 18:15:04 +0000
- Subject: [Bug math/16731] log(1) is -0, should be +0, in FE_DOWNWARD mode
- Auto-submitted: auto-generated
- References: <bug-16731-131 at http dot sourceware dot org/bugzilla/>
https://sourceware.org/bugzilla/show_bug.cgi?id=16731
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- Log -----------------------------------------------------------------
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=f7be737659813220e1f29c8850c386a9654d549a
commit f7be737659813220e1f29c8850c386a9654d549a
Author: Joseph Myers <joseph@codesourcery.com>
Date: Fri Mar 21 18:13:58 2014 +0000
Fix log (1) in round-downward mode (bug 16731).
According to ISO C Annex F, log (1) should be +0 in all rounding
modes, but some implementations in glibc wrongly return -0 in
round-downward mode (mapping to log1p (x - 1) is problematic because 1
- 1 is -0 in round-downward mode, and log1p (-0) is -0). This patch
fixes this. (It helps with some implementations of other functions
such as acosh, log2 and log10 that call out to log, but not enough to
enable all-rounding-modes testing for those functions without further
fixes to other implementations of them.)
Tested x86_64 and x86 and ulps updated accordingly, and did spot tests
for mips64 for the ldbl-128 fix, and i586 for the sysdeps/i386/fpu
implementations shadowed by those in sysdeps/i386/i686/fpu.
[BZ #16731]
* sysdeps/i386/fpu/e_log.S (__ieee754_log): Take absolute value
when x - 1 is zero.
* sysdeps/i386/fpu/e_logf.S (__ieee754_logf): Likewise.
* sysdeps/i386/fpu/e_logl.S (__ieee754_logl): Likewise.
* sysdeps/i386/i686/fpu/e_logl.S (__ieee754_logl): Likewise.
* sysdeps/ieee754/dbl-64/e_log.c (__ieee754_log): Return +0 when
argument is 1.
* sysdeps/ieee754/ldbl-128/e_logl.c (__ieee754_logl): Likewise.
* sysdeps/x86_64/fpu/e_logl.S: Take absolute value when x - 1 is
zero.
* math/libm-test.inc (log_test): Use ALL_RM_TEST.
* sysdeps/i386/fpu/libm-test-ulps: Update.
* sysdeps/x86_64/fpu/libm-test-ulps: Likewise.
-----------------------------------------------------------------------
Summary of changes:
ChangeLog | 17 +++++++++++++++++
NEWS | 2 +-
math/libm-test.inc | 4 +---
sysdeps/i386/fpu/e_log.S | 8 +++++++-
sysdeps/i386/fpu/e_logf.S | 8 +++++++-
sysdeps/i386/fpu/e_logl.S | 8 +++++++-
sysdeps/i386/fpu/libm-test-ulps | 12 ++++++++++++
sysdeps/i386/i686/fpu/e_logl.S | 8 +++++++-
sysdeps/ieee754/dbl-64/e_log.c | 4 ++++
sysdeps/ieee754/ldbl-128/e_logl.c | 2 ++
sysdeps/x86_64/fpu/e_logl.S | 8 +++++++-
sysdeps/x86_64/fpu/libm-test-ulps | 16 ++++++++++++++++
12 files changed, 88 insertions(+), 9 deletions(-)
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