------- Additional Comments From dberlin at gcc dot gnu dot org 2005-05-22
22:05 -------
Subject: Re: missed optimization due with
const function and pulling out of loops
On Sun, 2005-05-22 at 21:51 +0000, rakdver at atrey dot karlin dot mff
dot cuni dot cz wrote:
> ------- Additional Comments From rakdver at atrey dot karlin dot mff dot cuni
> dot cz 2005-05-22 21:50 -------
> Subject: Re: missed optimization due with const function and pulling out of
> loops
>
> > const is different from pure, const cannot read from memory.
>
> this is something that have been discussed many times; some people like
> the definition with "behaves like if" (that enables you for example to
> cache or precompute the results of the function) more, and it is used in
> several existing programs. Anyway, the argument that the function may
> be costly is valid regardless of whether you want to strictly enforce
> the no memory access constraint, or whether you use the more useful
> definition.
>
These people are strictly wrong, and will in fact get burned by the new
pure/const detection (which is better about recursive calls).
We shouldn't let people who have the wrong definition of const get in
the way of optimization
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21712
