http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59538
--- Comment #6 from Arsham Skrenes <arsham at skrenes dot com> ---
(In reply to Dominique d'Humieres from comment #5)
> > Also, is there a directive that I can use to explicitly tell GCC
> > to not remove a loop (without having to resort to a compiler flag
> > which is global, PRINTING A VARIABLE, or using the 'volatile' keyword
> > which de-optimizes the caching of the target variable)? Thanks!
>
> Try to print i instead of NTH! The basic way to avoid the removal of loops
> in a benchmark is to consume in some way some of the computed data (in some
> cases the optimizer may even be clever than you think).
Your solution is "printing a variable" which if you look at my question, is
exactly what I want to avoid. Before even writing that comment, I had already
added, after line 35, the following:
printf("%d\r",i);
It gets overwritten by the next print statement and retains the loop. It's a
hack and not at all elegant. That is why I'm asking if there is a compiler
directive I can use instead.
If one doesn't exist, there really ought to be a directive to retain a loop and
at the very least, such "optimizations" should output a warning (you shouldn't
be obliterating blocks of code without so much as a warning). The developer
should know if a block of code has been deemed unreachable or useless and
therefore not included.
