Re: Assuming optimization? What is best of these code alternatives?

[gautier_niouzes@hotmail.com]

Le jeudi 11 septembre 2014 15:14:39 UTC+2, reinkor a écrit :
> I am not sure to what extent one may assume the Ada compiler 
> makes optimization.  For example, assume the following two program 
> code alternatives:
[...]
>     k := i1 + i2; -- store "i1 + i2" in k to avoid recalculation (?)
>     loop
>       for i in k .. n loop

In any case the value i1 + i2 is the initial value for the loop, so even a totally non-optimizing compiler will compute the initial loop value once.
So in this case: the presence of k will be either, in terms of performance:
  - neutral (optimized compilation)
  - slighlty slower (a naive compiler will store i1 + i2 into k, then copy k into i when initializing the loop)
So here k will be only useful if you think it is more readable, especially if k could appears at many places.
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