[Bug tree-optimization/15911] VRP/DOM does not like TRUTH_AND_EXPR

[law at redhat dot com]

------- Comment #15 from law at redhat dot com  2006-03-21 16:57 -------
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.
How hard would it be to register the asserts for these dependency
change at the same time we register the initial assert.  It seems
there's only two cases we care about.

If we're asserting an SSA_NAME has a nonzero (true) value and the
SSA_NAME is defined by a TRUTH_AND_EXPR, then we know both operands
of the TRUTH_AND_EXPR must also be true (note we would then recurse
on the operands).

Similarly if we're asserting an SSA_NAME is zero (false) and the
SSA_NAME is defined by a TRUTH_OR_EXPR, then we know that both
operands of the TRUTH_OR_EXPR must also be zero (false).  Again
recurse on the operands.

I don't *think* it would be that hard.  

Jeff


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15911