https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99101
--- Comment #17 from Michael Matz <matz at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #16)
> Of course since -ffinite-loops and the C++ standard require forward progress
> here and all testcases expect the loop to not terminate we're in the realm
> of undefined behavior. But I'm not yet convinced the control-dependence /
> CD-DCE issue only shows up in such cases. That said, it's fully expected
> that
>
> int xx;
> int main()
> {
> int jobs_ = 1;
> int at_eof_ = 0;
> while (1)
> {
> for (int i = 0; i < jobs_; i++)
> {
> if (at_eof_)
> continue;
> at_eof_ = 1;
> if (xx)
> return 1;
> }
> jobs_ = 0;
> }
> return 0;
> }
>
> is eventually optimized to just return 1 with -ffinite-loops and we should
> try to preserve that behavior.
Just commenting on this last statement: I think that's wrong. It's provable
that 'xx' doesn't change in the loop, and that it starts out as 0 (this is main
here). So in fact we have produced an endless loop without a return, and hence
can do anything (when endless loops are undefined).
