Re: [patch] Call update_stmt in verify_ssa

[Zdenek Dvorak <rakdver at atrey dot karlin dot mff dot cuni dot cz>]

Hello,

> > > > this patch makes verify_ssa to call update_stmt on the statements it
> > > > verifies.  This helps to catch problems with updating of virtual
> > > > operands, concretely the situation where the memory reference is
> > > > modified in such a way that the virtual operands derived from it no
> > > > longer match the recorded virtual operands.
> > > > 
> > > > Bootstrapped & regtested on i686.  At the moment, this patch causes
> > > > basically all vectorizer tests to fail due to bug in vectorizer.
> > > 
> > > No, this is not ok.
> > > 
> > > By calling update_stmt on every stmt, you are going to cause the
> > > verifier to miss every other bug related to immediate uses and lack of
> > > lazy updating.   Any stmt which was left out-of-date by an optimization
> > > would now be updated by verify_ssa before we go looking for them.. 
> > > 
> > > Your bug is a different one. If you have changed a memory reference and
> > > need to assert that everything has been updated in this manner, I
> > > suggest something like calling verify_ssa at the end of your
> > > optimization (if checking is enabled), then do this loop to update all
> > > the stmts, and let the end-of-pass verify_ssa call ensure that
> > > everything is ok.
> > 
> > this does not seem like a good way to me.  This would need changes
> > wherever verify_ssa is used.  Perhaps verify_ssa should instead check
> > that all the operands are up-to-date?
> > 
> 
> Another alternative , if you want to check that calling update_stmt
> really DOESNT change anything in the operands cache at all, would be to
> add a new routine to the operand code which we could call to rebuild the
> stmt and compare it to the old operand cache, without actually changing
> the stmt.  verify_stmt_up2date() or some such thing.
> 
> Does this sounds more like what you are interested in?

yes, this is exactly what I propose in the previous paragraph.

Zdenek