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Re: [avr-gcc-list] May avr-libc use functions from libgcc?

From: Erik Christiansen
Subject: Re: [avr-gcc-list] May avr-libc use functions from libgcc?
Date: Sun, 7 Oct 2012 20:38:43 +1100
User-agent: Mutt/1.5.20 (2009-06-14)

On 07.10.12 10:25, Georg-Johann Lay wrote:
> Are such calls "allowed" in avr-libc provided
> - The special interface is documented in libgcc sources and mentions
>   that avr-libc makes use of the special interface
> - The functions with their special interface are documented, e.g. in
>   the GCC wiki

Well, that's how I would do it in a project of mine, FWIW.

> The question is for code that is not yet part of avr-libc, namely the
> upcoming fixed-point support; it's not about optimizing code that's
> already there.
> Sean said that CORDIC shows bad rounding for asin, for example.
> I played around with a home-brew asin approach that has no rounding
> issues.  The performance of the implementation can be improved if
> knowledge of libgcc is used.

Holy cow, the approach is fine, I figure, just from the perspectives of
consistent code behaviour and reuse. Add performance improvements and
your case is irresistible, I reckon.

I've only tried basic CORDIC to produce sin and cos. I didn't know that
asin was feasible with the method.


The tools we use have a profound and devious influence on our thinking
habits, and therefore on our thinking abilities.
                                                     -Edsgar W. Dijkstra

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