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

["jakub at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

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.