https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104800
--- Comment #28 from uecker at gcc dot gnu.org ---
(In reply to Richard Biener from comment #27)
> (In reply to uecker from comment #26)
> > (In reply to Richard Biener from comment #25)
> >
> > I assume ECF_LOOPING_CONST_OR_PURE means it can be assumed to read global
> > memory, so the store can not be sunk across the call and then eliminated.
> > So it seems ECF_LOOPING_CONST would sufficient (for C at least, not sure
> > about C++), but this does not exist. But I am just speculating based on the
> > comments in tree-core.h
>
> ECF_LOOPING_CONST doesn't exist, you imply
> ECF_CONST|ECF_LOOPING_CONST_OR_PURE,
Ah right.
> that would be sufficient for the testcase at hand I think.
>
> ECF_LOOPING_CONST_OR_PURE means the function might not return (it might
> contain a while(1) {} loop). That the function might not return is what we
> are
> really after as a property to properly inhibit the optimizations we do not
> want.
Sufficient for a modified test case with "volatile" on the variable. The
global write without volatile is ok to remove in C (but I need to check for
C++) and if I understand you correctly, changing to would
ECF_CONST|ECF_LOOPING_CONST_OR_PURE would allow this.
