Re: Sleazy FPU optimization

[Matt Thomas <matt%3am-software.com@localhost>]

On Feb 11, 2008, at 11:44 AM, David Laight wrote:

> On Mon, Feb 11, 2008 at 07:43:09PM +0100, Joerg Sonnenberger wrote:
> > On Mon, Feb 11, 2008 at 05:27:16PM +0000, Matthias Scheler wrote:
> > > Linux 2.6.20 and above has an interesting optimization for lazy FPU
> > > context saving:
> >
> > We've been discussing whether or not it is worth to do lazy FPU  
> > context
> > saving at all. Most programs will use the FPU on i386 anyway, e.g. if
> > printf is used. I'm not sure it will actually help.
>
> 1) Why would using printf for integers need the fpu

Because of va_list processing.  gcc may need to save/move FP registers
into order to pass a va_list