Re: weird optimization in sin+cos, x86 backend

[Andrew Haley <aph at redhat dot com>]

On 02/14/2012 04:54 PM, Geert Bosch wrote:
> 
> On Feb 14, 2012, at 11:44, Andrew Haley wrote:
> 
>> On 02/14/2012 04:41 PM, Geert Bosch wrote:
>>> Right now we don't have a library either that conforms to C99
>>
>> Are you sure?  As far as I know we do.  We might not meet
>> C99 Annex F, but that's not required.
>>
>>> and meets the far more relaxed accuracy criteria of OpenCL and
>>> Ada.
> Note the conjunctive "and" here. I was just replying to Vincent
> that it doesn't make sense to default to correctly rounded math
> yet, as we don't have such a thing.

I was confused: "either X and Y" is a very odd construct.  I don't
know what it means.  But to be absolutely clear, glibc's libm
doesn't have a problem meeting C99, AFAIK.

> I think it is feasible to integrate a libm meeting minimal
> accuracy requirements, as well as variations that additionally
> give much improved performance when non-default rounding modes,
> trapping and errno setting are not needed.

Probably.

> It still seems
> like glibc's libm is the best candidate to use a base.

That depends, because glibc's libm has such a wildly varying bunch
of implementations, particularly between 32- and 64-bit x86.

Andrew.