From: Jonathan Wakely <jwakely@redhat.com>
To: libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org
Subject: [committed] libstdc++: Remove __is_referenceable helper
Date: Thu, 1 Sep 2022 20:33:59 +0100 [thread overview]
Message-ID: <20220901193359.352625-1-jwakely@redhat.com> (raw)
Tested powerpc64le-linux, pushed to trunk.
-- >8 --
We only use the __is_referenceable helper in three places now:
add_pointer, add_lvalue_reference, and add_rvalue_reference. But lots of
other traits depend on add_[lr]value_reference, and decay depends on
add_pointer, so removing the instantiation of __is_referenceable helps
compile all those other traits slightly faster.
We can just use void_t<T&> to check for a referenceable type in the
add_[lr]value_reference traits.
Then we can specialize add_pointer for reference types, so that we don't
need to use remove_reference, and then use void_t<T*> for all
non-reference types to detect when we can form a pointer to the type.
libstdc++-v3/ChangeLog:
* include/std/type_traits (__is_referenceable): Remove.
(__add_lvalue_reference_helper, __add_rvalue_reference_helper):
Use __void_t instead of __is_referenceable.
(__add_pointer_helper): Likewise.
(add_pointer): Add partial specializations for reference types.
---
libstdc++-v3/include/std/type_traits | 37 ++++++++++++----------------
1 file changed, 16 insertions(+), 21 deletions(-)
diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index 3041ac3c941..8b11f31741b 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -712,18 +712,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// __void_t (std::void_t for C++11)
template<typename...> using __void_t = void;
-
- // Utility to detect referenceable types ([defns.referenceable]).
-
- template<typename _Tp, typename = void>
- struct __is_referenceable
- : public false_type
- { };
-
- template<typename _Tp>
- struct __is_referenceable<_Tp, __void_t<_Tp&>>
- : public true_type
- { };
/// @endcond
// Type properties.
@@ -1024,12 +1012,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
};
/// @cond undocumented
- template<typename _Tp, bool = __is_referenceable<_Tp>::value>
+ template<typename _Tp, typename = void>
struct __add_lvalue_reference_helper
{ using type = _Tp; };
template<typename _Tp>
- struct __add_lvalue_reference_helper<_Tp, true>
+ struct __add_lvalue_reference_helper<_Tp, __void_t<_Tp&>>
{ using type = _Tp&; };
template<typename _Tp>
@@ -1046,12 +1034,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
};
/// @cond undocumented
- template<typename _Tp, bool = __is_referenceable<_Tp>::value>
+ template<typename _Tp, typename = void>
struct __add_rvalue_reference_helper
{ using type = _Tp; };
template<typename _Tp>
- struct __add_rvalue_reference_helper<_Tp, true>
+ struct __add_rvalue_reference_helper<_Tp, __void_t<_Tp&&>>
{ using type = _Tp&&; };
template<typename _Tp>
@@ -1971,14 +1959,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
: public __remove_pointer_helper<_Tp, __remove_cv_t<_Tp>>
{ };
- template<typename _Tp, bool = __or_<__is_referenceable<_Tp>,
- is_void<_Tp>>::value>
+ template<typename _Tp, typename = void>
struct __add_pointer_helper
- { typedef _Tp type; };
+ { using type = _Tp; };
template<typename _Tp>
- struct __add_pointer_helper<_Tp, true>
- { typedef typename remove_reference<_Tp>::type* type; };
+ struct __add_pointer_helper<_Tp, __void_t<_Tp*>>
+ { using type = _Tp*; };
/// add_pointer
template<typename _Tp>
@@ -1986,6 +1973,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
: public __add_pointer_helper<_Tp>
{ };
+ template<typename _Tp>
+ struct add_pointer<_Tp&>
+ { using type = _Tp*; };
+
+ template<typename _Tp>
+ struct add_pointer<_Tp&&>
+ { using type = _Tp*; };
+
#if __cplusplus > 201103L
/// Alias template for remove_pointer
template<typename _Tp>
--
2.37.2
reply other threads:[~2022-09-01 19:34 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20220901193359.352625-1-jwakely@redhat.com \
--to=jwakely@redhat.com \
--cc=gcc-patches@gcc.gnu.org \
--cc=libstdc++@gcc.gnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).