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From: | Dave N6NZ |
Subject: | Re: [avr-gcc-list] GCC-AVR Register optimisations |
Date: | Wed, 09 Jan 2008 19:46:10 -0800 |
User-agent: | Thunderbird 1.5 (X11/20051201) |
Andrew Hutchinson wrote:
Hi all, just spend some days going over gcc-avr and missed optimizations.
Which is a huge bunch of work! Thanks! <snip>
The result is a 1.25% saving in code size for a simple mixed application. Pretty good for such a simple change!
Very good! What test cases were you using as a test case?1.25% code size is very significant, since it translates into a speed improvement as well, so 1.25% reduction of an inner loop can buy even more of a speed up.
For more floating point, the saving might well be higher as it demands more contiguous 32 bit registers.
That makes sense. I don't have any good test cases for 32 bit AVR code. But actually, simply measuring libm is probably a very good test case in a practical sense.
-dave
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