Re: [avr-gcc-list] GCC-AVR Register optimisations

[Dave N6NZ]

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