On Mon, 9 Nov 2015, Jason Merrill wrote:
> On 11/09/2015 02:28 PM, Jason Merrill wrote:
> > On 11/09/2015 04:08 AM, Richard Biener wrote:
> > > On Mon, 9 Nov 2015, Jason Merrill wrote:
> > >
> > > > I'm planning to merge the C++ delayed folding branch this week, but I
> > > > need to
> > > > get approval of the back end changes (the first patch attached).
> > > > Most of
> > > > these are the introduction of non-folding variants of convert_to_*,
> > > > but there
> > > > are a few others.
> > > >
> > > > One question: The branch changes 'convert' to not fold its result,
> > > > and it's
> > > > not clear to me whether that's part of the expected behavior of a
> > > > front end
> > > > 'convert' function or not.
> > >
> > > History. convert is purely frontend (but shared, unfortunately between
> > > all frontends). I would expect that FEs that do not do delayed folding
> > > expect convert to fold.
> > >
> > > > Also, I'm a bit uncertain about merging this at the end of stage 1,
> > > > since it's
> > > > a large internal change with relatively small user impact; it just
> > > > improves
> > > > handling of constant expression corner cases. I'm inclined to go
> > > > ahead with
> > > > it at this point, but I'm interested in contrary opinions.
> > >
> > > I welcome this change as it should allow cleaning up the FE-middle-end
> > > interface a bit more. It should be possible to remove all
> > > NON_LVALUE_EXPR adding/removal from the middle-end folders.
> > >
> > > Looks like the backend patch included frontend parts but as far as I
> > > skimmed it only
> > >
> > > diff --git a/gcc/fold-const.c b/gcc/fold-const.c
> > > index 5e32901..d754a90 100644
> > > --- a/gcc/fold-const.c
> > > +++ b/gcc/fold-const.c
> > > @@ -2091,6 +2091,17 @@ fold_convert_const (enum tree_code code, tree
> > > type,
> > > tree arg1)
> > > else if (TREE_CODE (arg1) == REAL_CST)
> > > return fold_convert_const_fixed_from_real (type, arg1);
> > > }
> > > + else if (TREE_CODE (type) == VECTOR_TYPE)
> > > + {
> > > + if (TREE_CODE (arg1) == VECTOR_CST
> > > + && TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE
> > > (arg1))
> > > + && TYPE_VECTOR_SUBPARTS (type) == VECTOR_CST_NELTS (arg1))
> > > + {
> > > + tree r = copy_node (arg1);
> > > + TREE_TYPE (arg1) = type;
> > > + return r;
> > > + }
> > > + }
> > >
> > >
> > > looks suspicious. The issue here is that the vector elements will
> > > have the wrong type after this simple handling.
> >
> > I was aiming to just handle simple cv-qualifier changes; that's why the
> > TYPE_MAIN_VARIANT comparison is there.
> >
> > > If you fix that you can as well handle all kind of element type
> > > changes via recursing to fold_convert_const (that includes
> > > float to int / int to float changes).
> >
> > But I'll try this.
>
> Like so?
Yes.
Thanks,
Richard.
