[PATCH] Fix devirtualization ICE (PR tree-optimization/59622, take 3)

Richard Biener rguenther@suse.de
Wed Jan 8 11:16:00 GMT 2014


On Wed, 8 Jan 2014, Richard Biener wrote:

> On Wed, 8 Jan 2014, Jakub Jelinek wrote:
> 
> > On Wed, Jan 08, 2014 at 11:45:28AM +0100, Richard Biener wrote:
> > > I prefer to always do this, not do the fancy insertion-before.  That
> > > would do repeated folding for
> > > 
> > >    fold_stmt (gsi);
> > >    fold_stmt (gsi);
> > >    fold_stmt (gsi);
> > > 
> > > where the last two should be a no-op.
> > 
> > I don't see how is that possible, at least for the __builtin_unreachable
> > case, because by just setting the fndecl to __builtin_unreachable and
> > keeping the incompatible fntype and bogus arguments for it all the
> > predicates whether it is a valid/suitable builtin call will fail and we
> > don't have a __builtin_unreachable function you could call.
> 
> Well, that just means we need two sets of predicates to check for
> a builtin call.  The __builtin_unreachable code wants to know what
> the callee is, not if that's a "valid" call to it.  But yeah - this
> starts to get confusing :/
> 
> > So at least for builtin we want to make sure it has the right parameters.
> > If the lhs is something we can just initialize to zero, we can replace the
> > call with zeroing the lhs, but that is no the case always.
> 
> I start to think this is a too complex transform for stmt folding ...

Alternatively do update_call_from_tree (gsi, get_or_create_ssa_default_def 
(cfun, create_tmp_var (TREE_TYPE (lhs)))).

> > For __cxa_pure_virtual we could just keep the code as is (just with the
> > !inplace addition and spelling fix?), but would need to fix up whatever ICEs
> > during checking on it to honor fntype rather than decl's type.
> 
> Yes.
> 
> So a patch just keeping the targets.length () == 1 case in folding
> with just replacing the fndecl of the call is ok.
> 
> Thanks,
> Richard.
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE / SUSE Labs
SUSE LINUX Products GmbH - Nuernberg - AG Nuernberg - HRB 16746
GF: Jeff Hawn, Jennifer Guild, Felix Imend"orffer



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