[Bug regression/24819] New: glibc math tests miscompiled with gcc-4.1

[Bug regression/24819] New: glibc math tests miscompiled with gcc-4.1

[olh at suse dot de]

make check fails with -O2 on powerpc64-linux and powerpc-linux with gcc-4.1
Works ok with gcc-4.0, and also with 4.1 and -O1.

ppc64:
make[2]: *** [/usr/src/packages/BUILD/glibc-2.3/cc-nptl/math/test-float.out]
Error 1
make[2]: *** [/usr/src/packages/BUILD/glibc-2.3/cc-nptl/math/test-double.out]
Error 1
make[2]: *** [/usr/src/packages/BUILD/glibc-2.3/cc-nptl/math/test-ifloat.out]
Error 1
make[2]: *** [/usr/src/packages/BUILD/glibc-2.3/cc-nptl/math/test-idouble.out]
Error 1
make[1]: *** [math/tests] Error 2

ppc:
make[2]: *** [/usr/src/packages/BUILD/glibc-2.3/cc-nptl/math/test-float.out]
Error 1
make[1]: *** [math/tests] Error 2

(make check runs without -k on ppc, the failure rate might be the same as on
ppc64).

Will post details and possible a testcase, later.


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           Summary: glibc math tests miscompiled with gcc-4.1
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: regression
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: olh at suse dot de
 GCC build triplet: powerpc-linux
  GCC host triplet: powerpc-linux
GCC target triplet: powerpc-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24819

[Bug regression/24819] glibc math tests miscompiled with gcc-4.1

[olh at suse dot de]

------- Comment #1 from olh at suse dot de  2005-11-12 14:07 -------
Created an attachment (id=10226)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=10226&action=view)
pr24819-failure.txt

make check errors on powerpc-linux


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24819

[Bug tree-optimization/24819] [4.1 Regression] glibc math tests miscompiled with gcc-4.1

[pinskia at gcc dot gnu dot org]

-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING
          Component|regression                  |tree-optimization
           Keywords|                            |wrong-code
            Summary|glibc math tests miscompiled|[4.1 Regression] glibc math
                   |with gcc-4.1                |tests miscompiled with gcc-
                   |                            |4.1


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24819

[Bug middle-end/24819] [4.1 Regression] glibc math tests miscompiled with gcc-4.1

[pinskia at gcc dot gnu dot org]

------- Comment #2 from pinskia at gcc dot gnu dot org  2005-11-12 15:31 -------
Waiting for a testcase.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|tree-optimization           |middle-end


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24819

[Bug middle-end/24819] [4.1 Regression] glibc math tests miscompiled with gcc-4.1

[pinskia at gcc dot gnu dot org]

-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.1.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24819

[Bug middle-end/24819] [4.1 Regression] glibc math tests miscompiled with gcc-4.1

[amodra at bigpond dot net dot au]

------- Comment #3 from amodra at bigpond dot net dot au  2005-11-16 11:42 -------
I analysed one of these failures quite a while ago.  The conclusion I came to
was that the errors were due to excess precision.  gcc-4.1 makes more use of
multiply-accumulate instructions.  You could try compiling glibc with
-mno-fused-madd.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24819

[Bug middle-end/24819] [4.1 Regression] glibc math tests miscompiled with gcc-4.1

[amodra at bigpond dot net dot au]

------- Comment #4 from amodra at bigpond dot net dot au  2005-11-16 11:44 -------
Marking as invalid given my previous analysis, and that the errors are all
1ulp.


-- 

amodra at bigpond dot net dot au changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24819

[Bug middle-end/24819] [4.1 Regression] glibc math tests miscompiled with gcc-4.1

[bonzini at gnu dot org]

------- Comment #5 from bonzini at gnu dot org  2005-11-25 19:12 -------
Another failure from glibc's tests is more severe: __DBL_MAX__ * __DBL_MAX__ -
__DBL_MAX * __DBL_MAX__ is turned into an INF rather than a NAN (as would
happen on most targets) or zero (as would happen on x87 because it computes
everything in long double).

This can be seen with a program like

  extern void abort (void)
  {
    double nan = __DBL_MAX__ * __DBL_MAX__ - __DBL_MAX * __DBL_MAX__;
    if (nan == nan && nan != 0.0) abort ();
  }

This seems more serious, to the point that fused multiply-add instructions
should be disabled unless !HONOR_NANS || !MODE_HAS_INFINITIES for the given
mode.

CCing Eric since he recently had problems with ia64 fma
(http://gcc.gnu.org/ml/gcc/2005-10/msg01036.html).


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bonzini at gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |amodra at bigpond dot net
                   |                            |dot au, bonzini at gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24819

[Bug middle-end/24819] [4.1 Regression] glibc math tests miscompiled with gcc-4.1

[bonzini at gnu dot org]

------- Comment #6 from bonzini at gnu dot org  2005-11-25 19:13 -------
CCing Eric since he recently had problems with ia64 fma
(http://gcc.gnu.org/ml/gcc/2005-10/msg01036.html).


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bonzini at gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ebotcazou at gcc dot gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24819