------- Comment #16 from law at redhat dot com 2006-03-22 04:57 -------
Subject: Re: VRP/DOM does not like
TRUTH_AND_EXPR
On Tue, 2006-03-21 at 16:19 +0000, dnovillo at gcc dot gnu dot org
wrote:
>
> ------- Comment #13 from dnovillo at gcc dot gnu dot org 2006-03-21 16:19
> -------
> (In reply to comment #12)
> > Any updates on this? It get's in the way of loop versioning conditionals
> > which
> > I now have to decompose manually into chained if's :/
> >
> Nope. I'm unlikely to work on this any time soon. Maybe in another couple of
> months.
FWIW, the idea of recursively creating asserts may work.
given something like
t1 = x > 10;
t2 = y < 30;
t3 = t1 && t2
if (t3)
First we insert any necessary asserts for T3 on the outgoing
edges. Then we look at how T3 is defined -- it's defined by
a TRUTH_AND_EXPR. So, we recurse on the arguments of the
TRUTH_AND_EXPR for the true edge.
We proceed to register that T1 must be true, and then recurse
on the definition of T1. That in turn allows us to realize
that x > 10 must be true as well, so we can register an assert
for x.
The same steps apply to t2.
The net result is that on the true edge we have the following
potential asserts
t3, t3 EQ 1
t1, t1 EQ 1
x, x > 10
t2, t2 EQ 1
y, y < 30
On the false edge we have
t3, t3 EQ 0
No other assertions are possible for the false edge.
There's still a number of loose ends to tie up, but this looks
rather promising and probably a lot easier than try to turn
this into a series of conditionals...
Jeff
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15911
