[PATCH] PPC64: First in the series of patches implementing POWER8 vector math.

[Joseph Myers]

On Mon, 18 Feb 2019, GT wrote:

> I have addressed all the issues you raised except for one. I haven't 
> been able to locate documentation which explains derivations of 
> corrections to some constants used in the x86_64 code. Corrections to PI 
> when used in repeated FMA operations, and corrections to 1/factorial(n) 
> coefficients in the approximation polynomial. I put the question of how 
> to obtain these derivations on the mailing list, and am also still 
> looking online for a solution. May I resubmit the patch or is the lack 
> of clarity regarding these constants a show-stopper?

Well, you could copy the comments from the x86_64 code, if these are the 
same constants.

I'd expect, for example, given the comments, that __dPI1_FMA + __dPI2_FMA 
+ __dPI3_FMA (using the x86_64 names) is an approximation to pi to about 
3*53 bits, which is something that should be easy to verify.

-- 
Joseph S. Myers
joseph@codesourcery.com