Re: weird optimization in sin+cos, x86 backend

[Vincent Lefevre <vincent+gcc at vinc17 dot org>]

On 2012-02-14 14:26:05 +0100, Vincent Lefevre wrote:
> On 2012-02-14 09:51:28 +0000, Andrew Haley wrote:
> > On 02/13/2012 08:00 PM, Geert Bosch wrote:
> > > GNU Linux is quite good, but has issues with the "pow" function for
> > > large exponents, even in current versions
> > 
> > Really?  Even on 64-bit?  I know this is a problem for the 32-bit
> > legacy architecture, but I thought the 64-bit pow() was OK.
> 
> According to http://sourceware.org/bugzilla/show_bug.cgi?id=706
> the 32-bit pow() can be completely wrong, and the 64-bit pow()
> is just very inaccurate.

Sorry, that's only for a 32-bit x86 machine, with the rounding
precision set to double and to extended. The x86_64 version
doesn't seem to have any problem in rounding to nearest (IIRC,
IBM's implementation is used, thus has problems with the directed
rounding modes).

-- 
Vincent Lefèvre <vincent@vinc17.net> - Web: <http://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <http://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)