Re: [avr-gcc-list] Gcc branches small comparison.

[David Brown]

> On Sunday 23 January 2005 16:44, Dmitry K. wrote:
> [...]
> >                 3.2.3   3.3.5   3.4.3   4.0     4.0-nrr
> >
> > do_random       102+14   91+10   93+10  173+14  173+14
>
> The reason is:
> avr-gcc 4.0 (20050116) replaces multiplication by a constant to a
combination
> of more simple operations. Thus it does not pay attention to efficiency of
> such replacement.
>
> For example:
>         int foo (int x) { return 24011 * x; }
> produce 49 words (-mmcu=atmega8 -Os).
> Older GCC branches -- only 11 words in this case.
>
> I have send the bug to gcc-buglist (#19597).
>

This sort of thing should really be controlled by a flag, since you might
want either behaviour.  Calling a routine will result in smaller code *if*
it can be used in more than one place in the program, while "unwrapped"
multiplications will be faster.