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Re: AArch64 patches for glibc master.

On 12/09/2013 04:40 PM, Joseph S. Myers wrote:
> On Mon, 9 Dec 2013, Carlos O'Donell wrote:
>>> * You're adding ulps for sqrt, which should always be exact.
>> I wasn't aware that sqrt should always be exact. I'll try to
>> educate myself on that. Do you have any pointers on where I can
>> read about that?
> If a function is bound to an IEC 60559 operation, it should always be 
> exact (correctly rounding according to the current rounding direction and 
> with a correct set of exceptions raised including "inexact" as 
> applicable).  For example, C11 F.3 says "The sqrt functions in <math.h> 
> provide the IEC 60559 square root operation.".  Other functions that 
> should never have ulps include rint, fma, scalbn.

Is this requirement because IEC 60559 requires everything to be correctly
rounded, therefore if C11 defines sqrt in terms of the IEC 60559 operation
then the function itself must be correctly rounding as required by the
standard (IEEE Std 754-2008)?


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