[Bug math/15487] New: math tests fail with older compilers on i386

[Bug math/15487] New: math tests fail with older compilers on i386

[andi-bz at firstfloor dot org]

http://sourceware.org/bugzilla/show_bug.cgi?id=15487

             Bug #: 15487
           Summary: math tests fail with older compilers on i386
           Product: glibc
           Version: 2.18
            Status: NEW
          Severity: normal
          Priority: P2
         Component: math
        AssignedTo: unassigned@sourceware.org
        ReportedBy: andi-bz@firstfloor.org
    Classification: Unclassified


Created attachment 7030
  --> http://sourceware.org/bugzilla/attachment.cgi?id=7030
gcc 4.6 failure 1

On a 32bit build I get a number of test suite failures in the math test suite
64bit is ok.

This started sometime a few months ago (?) I can bisect when there is interest.

They seem to be correlated with using older gcc. The failing systems have gcc
4.5 and gcc 4.6 (older Fedora). When I build with gcc 4.8 there are no
failures.

Interestingly the failures are not the same between 4.5 and 4.6

gcc 4.5.1 (FC14) fails test-double.out  test-ifloat.out
gcc 4.6.3 (FC16) fails test-float.out  test-ifloat.out

I'm attaching the test outputs.

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[Bug math/15487] math tests fail with older compilers on i386

[andi-bz at firstfloor dot org]

http://sourceware.org/bugzilla/show_bug.cgi?id=15487

--- Comment #1 from Andi Kleen <andi-bz at firstfloor dot org> 2013-05-17 19:24:29 UTC ---
Created attachment 7031
  --> http://sourceware.org/bugzilla/attachment.cgi?id=7031
gcc 4.6 failure 2

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[Bug math/15487] math tests fail with older compilers on i386

[andi-bz at firstfloor dot org]

http://sourceware.org/bugzilla/show_bug.cgi?id=15487

--- Comment #2 from Andi Kleen <andi-bz at firstfloor dot org> 2013-05-17 19:25:05 UTC ---
Created attachment 7032
  --> http://sourceware.org/bugzilla/attachment.cgi?id=7032
gcc 4.5 failure 1

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[Bug math/15487] math tests fail with older compilers on i386

[andi-bz at firstfloor dot org]

http://sourceware.org/bugzilla/show_bug.cgi?id=15487

--- Comment #3 from Andi Kleen <andi-bz at firstfloor dot org> 2013-05-17 19:25:16 UTC ---
Created attachment 7033
  --> http://sourceware.org/bugzilla/attachment.cgi?id=7033
gcc 4.5 failure 2

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[Bug math/15487] math tests fail with older compilers on i386

[carlos at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=15487

Carlos O'Donell <carlos at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |carlos at redhat dot com,
                   |                            |joseph at codesourcery dot
                   |                            |com

--- Comment #4 from Carlos O'Donell <carlos at redhat dot com> 2013-05-17 19:33:23 UTC ---
They are all 1, or 2 ulp at most in tgamma, cacos, or cacosh.

It would be interesting to see when these 1 or 2 ulp failures started.

I expect you'll find two patches, one effecting tgamma, the other related to
complex sinusoidal.

Joseph might know exactly what's going on though since he is the one making the
most changes in this code.

I've added Joseph to the CC.

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[Bug math/15487] math tests fail with older compilers on i386

[joseph at codesourcery dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=15487

--- Comment #5 from joseph at codesourcery dot com <joseph at codesourcery dot com> 2013-05-17 19:43:46 UTC ---
My suspicion is that this relates to differences in when each compiler 
uses excess precision, given that it's only for 32-bit and only for float 
and double not long double.

This does illustrate that when we regenerate the x86 / x86_64 ulps from 
scratch (which I think we should do at the start of the release freeze) it 
will be desirable to have not just people with different processors but 
also people with different GCC versions running the tests and adding ulps 
they see but other people don't.

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[Bug math/15487] math tests fail with older compilers on i386

[jsm28 at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=15487

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

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

--- Comment #6 from Joseph Myers <jsm28 at gcc dot gnu.org> ---
I don't think this sort of bug is useful in Bugzilla.  There's no indication of
a glibc bug, and ulps updates to account for different compilers / hardware are
best sent direct to libc-alpha (and can be committed as obvious unless the ulps
are excessive or the functions are ones such as rint, sqrt and fma that should
always be correctly rounded).

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[Bug math/15487] math tests fail with older compilers on i386

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=15487

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
              Flags|                            |security-

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