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Re: [C++ PATCH] Implement P0595R1 - so far as __builtin_is_constant_evaluated rather than std::is_constant_evaluated magic builtin
- From: Richard Biener <richard dot guenther at gmail dot com>
- To: Jakub Jelinek <jakub at redhat dot com>
- Cc: Jason Merrill <jason at redhat dot com>, Nathan Sidwell <nathan at acm dot org>, jwakely at redhat dot com, GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Mon, 23 Jul 2018 12:50:38 +0200
- Subject: Re: [C++ PATCH] Implement P0595R1 - so far as __builtin_is_constant_evaluated rather than std::is_constant_evaluated magic builtin
- References: <20180722193121.GC7166@tucnak> <CAFiYyc3-syZD8J=pgvg8mF0VQiB56wxu=2CO5=eKp4Hm3bfAJg@mail.gmail.com> <20180723102812.GH7166@tucnak>
On Mon, Jul 23, 2018 at 12:28 PM Jakub Jelinek <email@example.com> wrote:
> On Mon, Jul 23, 2018 at 12:17:42PM +0200, Richard Biener wrote:
> > > Bootstrapped/regtested on x86_64-linux.
> > Thanks for working on this. I wonder if we can completely hide this
> > from the middle-end, without requiring defining of c_dialect_cxx.
> > There is the BUILT_IN_FRONTEND class so you could somewhere
> > manually inject a decl in that class for C++?
> But then I couldn't handle folding of the builtin in the middle-end to false,
> which is what I need (because in the FE it needs to be either folded to
> true, or its folding deferred until later).
> Or maybe in the C++ gimplification langhook?
Yes, I was thinking the C++ langhook or its fully_fold routine.
> Seems we have a single BUILT_IN_FRONTEND builtin in the whole compiler,
> __integer_pack, but it doesn't act as a normal builtin, given it is a
> templatish magic.
Yeah, I think at some point we considered removing BUILT_IN_FRONTEND ...
Nowadays internal-use builtins can easily be internal-functions but of couse
this one will eventually be used from libstdc++.