Re: [rtl] Integer Math instruction execution times

[Tomasz Motylewski <motyl@stan.chemie.unibas.ch>]

On Fri, 24 Apr 1998, C. W. Wright (1698) wrote:

> static int i,j,k,l;
> The variables had to be declared static, or else the compiler was not
> generating instructions for the action.  I discovered because the pulse
> width on the scope was not changing when the action inside the loop was
> changed.  In fact, the time was exactly the same no matter what was done
> inside the loop!  Upon running gcc -O2 -S sra_irq.c and examining the
> assembly source, I discovered that no code was generated for the action.

This is normal gcc optimization. What should be used is "volatile"
declaration - static worked just accidentally, better (globally
optimizing) compiler would eliminate also that. 

Did you check what is the delay without any loop at all ?

Quite interesing result.

--
Tomasz Motylewski


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