This is the mail archive of the glibc-bugs@sourceware.org mailing list for the glibc project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

[Bug math/14797] New: fma use of a * b + c on overflow incorrect in directed rounding modes


http://sourceware.org/bugzilla/show_bug.cgi?id=14797

             Bug #: 14797
           Summary: fma use of a * b + c on overflow incorrect in directed
                    rounding modes
           Product: glibc
           Version: 2.16
            Status: NEW
          Severity: normal
          Priority: P2
         Component: math
        AssignedTo: unassigned@sourceware.org
        ReportedBy: jsm28@gcc.gnu.org
    Classification: Unclassified


Various fma implementations fall back to a * b + c when a * b is known to
overflow so much that the final result would still overflow, whatever the value
of c.  But this is incorrect in directed rounding modes where a * b may not be
an infinity.  Example using dbl-64/s_fma.c: fma (DBL_MAX, DBL_MAX, -DBL_MIN)
should return DBL_MAX in FE_DOWNWARD mode but returns the next smaller
floating-point number instead.

-- 
Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]