[Bug math/18612] New: ldbl-128 j1l spurious underflows

[Bug math/18612] New: ldbl-128 j1l spurious underflows

[jsm28 at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=18612

            Bug ID: 18612
           Summary: ldbl-128 j1l spurious underflows
           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
  Target Milestone: ---

The ldbl-128 implementation of j1l produces spurious underflow exceptions for
some small arguments, e.g. on mips64:

Failure: j1 (0x1p-10000): Exception "Underflow" set

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[Bug math/18612] ldbl-128 j1l spurious underflows

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=18612

--- Comment #1 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
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The branch, master has been updated
       via  4aa10d01b654b7395c6e856b8e1e0959cfc80739 (commit)
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- Log -----------------------------------------------------------------
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=4aa10d01b654b7395c6e856b8e1e0959cfc80739

commit 4aa10d01b654b7395c6e856b8e1e0959cfc80739
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Mon Jun 29 17:51:32 2015 +0000

    Fix ldbl-128 j1l spurious underflows (bug 18612).

    The ldbl-128 implementation of j1l produces spurious underflow
    exceptions for some small arguments, as a result of squaring the
    argument.  This patch fixes it just to use a linear approximation for
    sufficiently small arguments, and then to force an underflow exception
    only in the cases where it is required.

    Tested for mips64.

        [BZ #18612]
        * sysdeps/ieee754/ldbl-128/e_j1l.c (__ieee754_j1l): For small
        arguments, just return 0.5 times the argument, with underflow
        forced as needed.
        * math/auto-libm-test-in: Add more tests of j1.
        * math/auto-libm-test-out: Regenerated.

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

Summary of changes:
 ChangeLog                        |    7 ++
 NEWS                             |    2 +-
 math/auto-libm-test-in           |    3 +
 math/auto-libm-test-out          |  175 ++++++++++++++++++++++++++++++++++++++
 sysdeps/ieee754/ldbl-128/e_j1l.c |   10 ++
 5 files changed, 196 insertions(+), 1 deletions(-)

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[Bug math/18612] ldbl-128 j1l spurious underflows

[jsm28 at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=18612

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

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

--- Comment #2 from Joseph Myers <jsm28 at gcc dot gnu.org> ---
Fixed for 2.22.

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