On Wed, Mar 18, 2015 at 11:08:15AM +0100, Richard Biener wrote:
> On Fri, Mar 13, 2015 at 3:40 PM, Marek Polacek <pola...@redhat.com> wrote:
> > We started to reject this (IMHO valid) testcase with r214941 that did away
> > with
> > try_move_mult_to_index -- meaning that we are no longer able to fold
> > *(&s[0] + 1)
> > into s[1], while we are able to fold *(s + 1) into s[1].
> >
> > I suppose cxx_fold_indirect_ref ought to be able to handle both cases, so I
> > added
> > some code to that effect, it should handle now at least the simple cases...
> > Or should that be handled in the middle end?
>
> It's "correct" for constexpr folding but not correct to hand s[1] down to
> the middle-end IL (both cases). Well, in the particular case with
> in-array-bound constant and a non-pointer base it's good enough at
> least.
I believe cxx_fold_indirect_ref result is not passed through to the
middle-end, unless it can be folded into a constant.
Though, a question is if we do (or, if we don't and should) reject say
constexpr char s[] = "abc";
constexpr int j = 4;
constexpr char c = *(&s[j] - 2);
because there was out of bound access in there.
Jakub
