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Re: Tree-SSA self checking infrastructure
- From: law at redhat dot com
- To: Jan Hubicka <hubicka at ucw dot cz>
- Cc: Richard Henderson <rth at redhat dot com>, Jan Hubicka <jh at suse dot cz>, gcc at gcc dot gnu dot org
- Date: Wed, 19 Nov 2003 14:44:45 -0700
- Subject: Re: Tree-SSA self checking infrastructure
- Reply-to: law at redhat dot com
In message <20031119213603.GW16923@atrey.karlin.mff.cuni.cz>, Jan Hubicka write
s:
>I am doing the first, how can I implement the second? That may be
>actually one problems I am seeing...
>(given the fact that only the tail recursion ellimination run as very
>last pass before de-ssa breaks I think it is actually not the case, but
>definitly needs to be done right)
I'm not absolutely sure myself. Again, my recollection is a bit fuzzy, but
I think people have argued that you do want those PHI nodes for the meet
between the uninitialized path and the initialized path. But before you
spend a lot of time on it, you might want to do a little research.
It's also worth noting that we don't seem to be creating PHIs for this
right now. Consider:
foo(x)
{
int a;
label:
a = 20;
goto label;
}
We don't get a PHI at "label" -- so even if it is recommended that we
have PHIs at the join point between initialized and uninitialized, it
doesn't appear that we currently do it.
jeff