[Bug math/19003] New: [x86_64] fma4 version of pow inappropriate contraction

[Bug math/19003] New: [x86_64] fma4 version of pow inappropriate contraction

[jsm28 at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=19003

            Bug ID: 19003
           Summary: [x86_64] fma4 version of pow inappropriate contraction
           Product: glibc
           Version: 2.22
            Status: NEW
          Severity: normal
          Priority: P2
         Component: math
          Assignee: unassigned at sourceware dot org
          Reporter: jsm28 at gcc dot gnu.org
  Target Milestone: ---
              Host: x86_64-*-*

The x86_64 fma4 version of pow fails to disable contraction of operations other
than those explicitly intended to use fma instructions, so resulting in large
ulps errors on processors with fma4 instructions, as in bug 18104 (165ulp for
the test added for that bug).

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[Bug math/19003] [x86_64] fma4 version of pow inappropriate contraction

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=19003

--- 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  51df2605064a2bfd44fa0655ef9815812347de80 (commit)
      from  24ffcbfc24e08212cc5b1fa8318940e75b06313c (commit)

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https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=51df2605064a2bfd44fa0655ef9815812347de80

commit 51df2605064a2bfd44fa0655ef9815812347de80
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Thu Sep 24 16:48:32 2015 +0000

    Fix x86_64 fma4 pow inappropriate contraction (bug 19003).

    The x86_64 fma4 version of pow fails to disable contraction of
    operations other than those explicitly intended to use fma
    instructions, so resulting in large ulps errors on processors with
    fma4 instructions, as in bug 18104 (165ulp for the test added for that
    bug; error originally reported by "blaaa" on #glibc).  This patch adds
    $(config-cflags-nofma) for e_pow-fma4.c, corresponding to the use for
    e_pow.c in sysdeps/ieee754/dbl-64/Makefile.

    Tested for x86_64 on a processor with fma4.

        [BZ #19003]
        * sysdeps/x86_64/fpu/multiarch/Makefile (CFLAGS-e_pow-fma4.c): Add
        $(config-cflags-nofma).

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

Summary of changes:
 ChangeLog                             |    6 ++++++
 NEWS                                  |    2 +-
 sysdeps/x86_64/fpu/multiarch/Makefile |    2 +-
 3 files changed, 8 insertions(+), 2 deletions(-)

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[Bug math/19003] [x86_64] fma4 version of pow inappropriate contraction

[jsm28 at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=19003

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED
   Target Milestone|---                         |2.23

--- Comment #2 from Joseph Myers <jsm28 at gcc dot gnu.org> ---
Fixed for 2.23.

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