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[Bug math/3268] New: fma for soft-fp is not correct.


The current ./math/s_fma[fl].c implementation simply implements:

double
__fma (double x, double y, double z)
{
  return (x * y) + z;
}

Which does mot meet the requirement of 754r

"fused multiply-add: The operation fma(x,y,z) computes (x ×y )+z as if with
unbounded range and precision, rounding only once to the destination format; see
subclause 5.1."

This implies (for example) that for double that the 106 bit result of the
multiply be passed unrounded to the add (53 bit) and then final result found to
53 bits.

-- 
           Summary: fma for soft-fp is not correct.
           Product: glibc
           Version: 2.4
            Status: NEW
          Severity: normal
          Priority: P2
         Component: math
        AssignedTo: aj at suse dot de
        ReportedBy: sjmunroe at us dot ibm dot com
                CC: glibc-bugs at sources dot redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=3268

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