[ARMedslack] mfloat-abi

Thorsten Mühlfelder thenktor at gmx.de
Fri Feb 4 09:59:20 UTC 2011

Am Friday 28 January 2011 12:39:34 schrieb Stuart Winter:
> > - soft: only software emulation
> > - softfp + mfpu=xxx: enables the compiler to use FP
> > instructions/registers inside functions, but not as function
> > parameters. This way, code remains compatible with 'soft' libraries
> > - hard: it's a different ABI, where parameters can be passed in FP
> > registers, avoiding expensive moves between core and FP registers. But
> > such code is not compatible with 'soft' libraries.
> You can also do
> gcc -dumpspecs
> to see what the compiler's defaults are.

Hmm, I did not really see what's the default here (soft, softfp, hard)?

BTW: A test with Ogg Vorbis decoding using mpd on my Dockstar gave me these 
- using libvorbis (floating point): ~20% CPU usage
- using tremor (vorbis ported to integer only): ~2% CPU usage

As soft/softfpe is some kind of porting floating point operations to integer 
I've assumed that Armed Slack uses mfloat-abi=hard, which forwards the 
floating point instructions to the slow kernel FP emulation.

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