From: Marc Glisse <marc.glisse@inria.fr>
To: Ken Matsui <kmatsui@cs.washington.edu>
Cc: gcc-patches@gcc.gnu.org, libstdc++@gcc.gnu.org, ppalka@redhat.com
Subject: Re: [PATCH 2/2] libstdc++: use new built-in trait __add_const
Date: Tue, 21 Mar 2023 12:20:42 +0100 (CET) [thread overview]
Message-ID: <19d13f2f-65e5-2851-26aa-439ebd90813f@inria.fr> (raw)
In-Reply-To: <20230321111056.78121-2-kmatsui@cs.washington.edu>
On Tue, 21 Mar 2023, Ken Matsui via Libstdc++ wrote:
> /// add_const
> +#if __has_builtin(__add_const)
> + template<typename _Tp>
> + struct add_const
> + { using type = __add_const(_Tp); };
> +#else
> template<typename _Tp>
> struct add_const
> { using type = _Tp const; };
> +#endif
Is that really better? You asked elsewhere if you should measure for each
patch, and I think that at least for such a trivial case, you need to
demonstrate that there is a point. The drawbacks are obvious: more code in
libstdc++, non-standard, and more builtins in the compiler.
Using builtins makes more sense for complicated traits where you can save
several instantiations. Now that you have done a couple simple cases to
see how it works, I think you should concentrate on the more complicated
cases.
--
Marc Glisse
next prev parent reply other threads:[~2023-03-21 11:20 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-21 11:10 [PATCH 1/2] c++: implement __add_const built-in trait Ken Matsui
2023-03-21 11:10 ` [PATCH 2/2] libstdc++: use new built-in trait __add_const Ken Matsui
2023-03-21 11:20 ` Marc Glisse [this message]
2023-03-21 11:24 ` Jonathan Wakely
2023-03-21 11:37 ` Ken Matsui
2023-03-21 11:26 ` [PATCH 1/2] c++: implement __add_const built-in trait Jonathan Wakely
2023-03-21 11:29 ` Jonathan Wakely
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