Re: Fixed point cairo.. or no cairo?

[Behdad Esfahbod <behdad behdad org>]

On Mon, 2006-08-21 at 19:16 -0400, Aivars Kalvans wrote:
> Behdad Esfahbod wrote:
> >   - If I compile with anything other than -O0, I get all zeros printed.
> > Any optimization level makes gcc drop the inline assembly away.
> > Incidentally, no optimization is hardly the best thing to profile.
> >   
> Adding "volatile" will keep assembly:

Ah, I tried "volatile asm" and that didn't work...

This just confirmed that an optimized branch on x86 is basically free:

overhead:               43 cycles
overhead:               43 cycles
branching:              43 cycles
branching:              51 cycles
function call:          77 cycles
inline multiply:        60 cycles

The overhead is constant on 43.  The branching cost goes up and down,
but a lot of times I get 43, which means the conditional is essentially
free in the pipeline.

> asm volatile (".byte 0x0f, 0x31" : "=A" (start));
> 
-- 
behdad
http://behdad.org/

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