[maemo-developers] Performance of floating point instructions

[From: Kimmo Hämäläinen]

On Wed, 2010-03-10 at 12:57 +0100, ext Alberto Mardegan wrote:
> Kimmo Hämäläinen wrote:
> > You can also put the CPU to a "fast floats" mode, see hd_fpu_set_mode()
> > in
> > http://maemo.gitorious.org/fremantle-hildon-desktop/hildon-desktop/blobs/master/src/main.c
> > 
> > N900 has support for NEON instructions also.
> 
> This sounds interesting!
> 
> Is there any performance penalty if this switch is done often?

IIRC, there was not. Leonid Moiseichuk was testing this about a year
ago, and he noticed almost 50% speed-up for floats. Notice that this
affects only floats, not doubles, and that there is a small accuracy
penalty.

-Kimmo