[Bug c++/71372] [6/7 Regression] C++ FE drops TREE_THIS_VOLATILE in cp_fold on all tcc_reference trees

[rguenther at suse dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71372

--- Comment #10 from rguenther at suse dot de <rguenther at suse dot de> ---
On Thu, 2 Jun 2016, jakub at gcc dot gnu.org wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71372
> 
> --- Comment #9 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
> (In reply to rguenther@suse.de from comment #8)
> > On Thu, 2 Jun 2016, rguenther at suse dot de wrote:
> > Actually it's not a bug of those but of the callers (given fold_binary
> > doesn't get to see that flag).
> 
> Exactly.
> > 
> > > > see just
> > > >       switch (TREE_CODE_LENGTH (code))
> > > >         {
> > > >         case 1:
> > > >           op0 = TREE_OPERAND (t, 0);
> > > >           tem = fold_unary_loc (loc, code, type, op0);
> > > >           return tem ? tem : expr;
> > > >         case 2:
> > > >           op0 = TREE_OPERAND (t, 0);
> > > >           op1 = TREE_OPERAND (t, 1);
> > > >           tem = fold_binary_loc (loc, code, type, op0, op1);
> > > >           return tem ? tem : expr;
> > > >         case 3:
> > > >           op0 = TREE_OPERAND (t, 0);
> > > >           op1 = TREE_OPERAND (t, 1);
> > > >           op2 = TREE_OPERAND (t, 2);
> > > >           tem = fold_ternary_loc (loc, code, type, op0, op1, op2);
> > > >           return tem ? tem : expr;
> > > > without really trying to preserve anything.
> > 
> > This would need to do the fixup in case of tcc_reference codes.  
> > Fortunately fold () calls are rare.
> 
> Well, both C and C++ FEs now call them pretty much on everything.  So certainly
> not rare.

(something to fix)

Well.  So we need to fixup things in fold () - that part is latent
everywhere then.  But the actual issue for the testcaseis in cp_fold.