[Bug math/18030] New: [ldbl-128ibm] logbl wrong near powers of 2

[Bug math/18030] New: [ldbl-128ibm] logbl wrong near powers of 2

[jsm28 at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=18030

            Bug ID: 18030
           Summary: [ldbl-128ibm] logbl wrong near powers of 2
           Product: glibc
           Version: 2.21
            Status: NEW
          Severity: normal
          Priority: P2
         Component: math
          Assignee: unassigned at sourceware dot org
          Reporter: jsm28 at gcc dot gnu.org

Similar to bug 18029 for ilogbl, the ldbl-128ibm implementation of logbl
produces incorrect results when the high part of the argument is a power of 2
and the low part a nonzero number with the opposite sign (and so the returned
exponent should be 1 less than that of the high part).  For example, logbl
(0x1.ffffffffffffffp1L) returns 2 but should return 1.

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[Bug math/18030] [ldbl-128ibm] logbl wrong near powers of 2

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=18030

--- Comment #1 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
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The branch, master has been updated
       via  524ae9ea2e3ae9f5bf5d655595fda827e9dc50a1 (commit)
      from  23d43090e0b275e47e09e859823e965a1eb323dc (commit)

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- Log -----------------------------------------------------------------
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=524ae9ea2e3ae9f5bf5d655595fda827e9dc50a1

commit 524ae9ea2e3ae9f5bf5d655595fda827e9dc50a1
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Thu Feb 26 12:57:21 2015 +0000

    Fix ldbl-128ibm ilogbl near powers of 2 (bug 18029).

    The ldbl-128ibm implementation of ilogbl produces incorrect results
    when the high part of the argument is a power of 2 and the low part a
    nonzero number with the opposite sign (and so the returned exponent
    should be 1 less than that of the high part).  For example, ilogbl
    (0x1.ffffffffffffffp1L) returns 2 but should return 1.  (This is
    similar to (fixed) bug 16740 for frexpl, and bug 18030 for logbl.)
    This patch adds checks for that case.

    Tested for powerpc.

        [BZ #18029]
        * sysdeps/ieee754/ldbl-128ibm/e_ilogbl.c (__ieee754_ilogbl):
        Adjust exponent of power of 2 down when low part has opposite
        sign.
        * math/libm-test.inc (ilogb_test_data): Add more tests.

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog                              |    8 ++++++++
 NEWS                                   |    2 +-
 math/libm-test.inc                     |    5 +++++
 sysdeps/ieee754/ldbl-128ibm/e_ilogbl.c |   23 +++++++++++++++++++----
 4 files changed, 33 insertions(+), 5 deletions(-)

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[Bug math/18030] [ldbl-128ibm] logbl wrong near powers of 2

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=18030

--- Comment #2 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, master has been updated
       via  380bd0fd2418f8988217de950f8b8ff18af0cb2b (commit)
      from  4a28f4d55a6cc33474c0792fe93b5942d81bf185 (commit)

Those revisions listed above that are new to this repository have
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- Log -----------------------------------------------------------------
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=380bd0fd2418f8988217de950f8b8ff18af0cb2b

commit 380bd0fd2418f8988217de950f8b8ff18af0cb2b
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Thu Feb 26 15:13:22 2015 +0000

    Fix ldbl-128ibm logbl near powers of 2 (bug 18030).

    The ldbl-128ibm implementation of logbl produces incorrect results
    when the high part of the argument is a power of 2 and the low part a
    nonzero number with the opposite sign (and so the returned exponent
    should be 1 less than that of the high part).  For example, logbl
    (0x1.ffffffffffffffp1L) returns 2 but should return 1.  (This is
    similar to (fixed) bug 16740 for frexpl, and (fixed) bug 18029 for
    ilogbl.)  This patch adds checks for that case.

    Tested for powerpc.

        [BZ #18030]
        * sysdeps/ieee754/ldbl-128ibm/s_logbl.c (__logbl): Adjust exponent
        of power of 2 down when low part has opposite sign.
        * math/libm-test.inc (logb_test_data): Add more tests.

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog                             |    7 +++++++
 NEWS                                  |    2 +-
 math/libm-test.inc                    |    5 +++++
 sysdeps/ieee754/ldbl-128ibm/s_logbl.c |   17 ++++++++++++++---
 4 files changed, 27 insertions(+), 4 deletions(-)

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[Bug math/18030] [ldbl-128ibm] logbl wrong near powers of 2

[jsm28 at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=18030

Joseph Myers <jsm28 at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #3 from Joseph Myers <jsm28 at gcc dot gnu.org> ---
Fixed for 2.22.

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