------- Comment #7 from rakdver at atrey dot karlin dot mff dot cuni dot cz
2006-11-06 12:33 -------
Subject: Re: Missed constant propagation into loops
> But obviously for real operands, foo () won't clobber them. I.e. the
> following
> also could be optimized but is not:
>
> void foo (int *);
> void bar (void)
> {
> int j;
> int i;
> i = 0;
> for (j = 0; j < 10000; j++)
> if (i)
> foo (&i);
> }
>
> foo () will be never executed, so the clobbering of i is not "executed",
> so we don't need i as PHI arg/result for the loop. This is what I'm looking
> for as optimization.
now you have lost me, I have no idea what you are trying to tell. What
I mean is that this is exactly the same case like
void bar (void)
{
int j;
int i;
i = 0;
for (j = 0; j < 10000; j++)
if (i)
i = 1;
}
Except that in the testcase for the PR, "i" is not a real operand.
Since we already have some support for virtual operands in ccp, it
should not be too difficult to make it handle this case as well.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29738
