[Bug math/3268] fma for all targets without hardware fma instructions is incorrect.

["sjmunroe at us dot ibm dot com" <sourceware-bugzilla at sourceware dot org>]

------- Additional Comments From sjmunroe at us dot ibm dot com  2007-02-06 16:30 -------
Yes what you suggest should work for the generic s_fmaf.c, but that is not the
current implmentation. Also fmasf4.c should be a little faster as it avoids some
of the more expensive intermediate conversions.

s_fma.c would be more problematic because it would require full IEEE quad and TF
type support. I believe that you youself pointed out that not all platforms
support IEEE quad/TF type, but those platforms still need fma() to work correctly. 

That is why I reworked the patch to avoid internal use of TF typs and support
direct RAW/SEMIRAW/CANNONICAL conversion for the intermediate steps of the
soft-fp fma. Again fmadf4.c should be faster then the generic.

Yes in the long run we will need to address soft-fp fmal but that requires the
invention of "oct or long long double" format. Most platforms that need soft-fp
don't implement long double 128-bit so we stage that function. 

But we have a fix for soft-fp float and double now. I don't see any reason to delay.

-- 


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

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