From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by sourceware.org (Postfix) with ESMTPS id 8C88A3870899 for ; Thu, 13 Jun 2024 12:31:46 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 8C88A3870899 Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=redhat.com ARC-Filter: OpenARC Filter v1.0.0 sourceware.org 8C88A3870899 Authentication-Results: server2.sourceware.org; arc=none smtp.remote-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1718281910; cv=none; b=G6pqw0p7PTpUCrHlMHTt/DX5F6XKX46X2Yx+8AY3XMPKQZYXv74b/pkmjwhIKWWD+89m0rd9g9Ro3hcKbs8xUpEYyRPhd7pV2u8GxkmG3e8HmvbGBYNW84wHu/JnjbXXqw2z23QHNs9hY4AVR7415N4Uug27U3acPuol0YRF7UQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1718281910; c=relaxed/simple; bh=F/nAlO7QaIaYJsNCe+vmTyN1nW0Dz86G7Ke+dPxiCAI=; h=DKIM-Signature:Date:From:To:Subject:Message-ID:MIME-Version; b=leDSN35tU9Ts5lJpWWBB+8D4irRIMdeGe3shFuzI8/dGNwKKehqEkKWugafWZZ+n54xuWZuhnixUX5te0JeJp+jN6MX8aXkEUjYeYa5mPe+OhfLTbDSta/3vV3rYFl6yIQaQIrwHefkE0kTVv06pV/28qfvMCt8kuLSwJVyaAXQ= ARC-Authentication-Results: i=1; server2.sourceware.org DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1718281906; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Dh+9yokd1TUVyjZU5bDdPW8lkNE/WxsMaGCaGA7Ypz0=; b=HTWAIKY39NlAxTRdUpKLA5tKXSWaxcJ2cBAphEgBW24HHmdK7IVuUuVR/TmeMwFIe53U0Q VtoT0f4hpiMbIW+wDV0LsME75F7DRJQ4L786cL8MQszbmEzVyYgYxKBhGSV6D2Xsnfhp7F MIVcb3vfvbunBHJGVofPC7xCLG7gaVo= Received: from mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-577-GRAnq-B3M3W6A5l7NxAmCA-1; Thu, 13 Jun 2024 08:31:44 -0400 X-MC-Unique: GRAnq-B3M3W6A5l7NxAmCA-1 Received: from mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.40]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id A3B6719560A0; Thu, 13 Jun 2024 12:31:43 +0000 (UTC) Received: from localhost (unknown [10.39.192.128]) by mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id BBEA819560AE; Thu, 13 Jun 2024 12:31:42 +0000 (UTC) Date: Thu, 13 Jun 2024 13:31:41 +0100 From: Jonathan Wakely To: Ken Matsui Cc: gcc-patches@gcc.gnu.org, libstdc++@gcc.gnu.org Subject: Re: [PATCH v26 03/13] libstdc++: Optimize std::is_pointer compilation performance Message-ID: References: <20240510161405.194750-21-kmatsui@gcc.gnu.org> <20240511090130.248174-1-kmatsui@gcc.gnu.org> <20240511090130.248174-3-kmatsui@gcc.gnu.org> MIME-Version: 1.0 In-Reply-To: <20240511090130.248174-3-kmatsui@gcc.gnu.org> X-Clacks-Overhead: GNU Terry Pratchett X-Scanned-By: MIMEDefang 3.0 on 10.30.177.40 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline X-Spam-Status: No, score=-10.8 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,GIT_PATCH_0,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H4,RCVD_IN_MSPIKE_WL,RCVD_IN_SBL_CSS,SPF_HELO_NONE,SPF_NONE,TXREP,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On 11/05/24 02:01 -0700, Ken Matsui wrote: >This patch optimizes the compilation performance of std::is_pointer >by dispatching to the new __is_pointer built-in trait. > >libstdc++-v3/ChangeLog: > > * include/bits/cpp_type_traits.h (__is_pointer): Use > __is_pointer built-in trait. Optimize its implementation. > * include/std/type_traits (is_pointer): Likewise. > (is_pointer_v): Likewise. > >Co-authored-by: Jonathan Wakely >Signed-off-by: Ken Matsui >--- > libstdc++-v3/include/bits/cpp_type_traits.h | 31 ++++++++++++++- > libstdc++-v3/include/std/type_traits | 44 +++++++++++++++++---- > 2 files changed, 66 insertions(+), 9 deletions(-) > >diff --git a/libstdc++-v3/include/bits/cpp_type_traits.h b/libstdc++-v3/include/bits/cpp_type_traits.h >index 59f1a1875eb..210a9ea00da 100644 >--- a/libstdc++-v3/include/bits/cpp_type_traits.h >+++ b/libstdc++-v3/include/bits/cpp_type_traits.h >@@ -363,6 +363,13 @@ __INT_N(__GLIBCXX_TYPE_INT_N_3) > // > // Pointer types > // >+#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_pointer) >+ template >+ struct __is_pointer : __truth_type<_IsPtr> I was worried that reusing __is_pointer this way would cause a problem with Clang, because it has an __is_pointer built-in and the code above causes a warning: isp.cc:2:12: warning: keyword '__is_pointer' will be made available as an identifier for the remainder of the translation unit [-Wkeyword-compat] 2 | struct __is_pointer | ^ I thought this warning meant it was only available as an identifier. But in fact it becomes available as both an identifier and as the built-in. This is what I tested: template struct __is_pointer { enum { value = IsPtr }; }; static_assert( __is_pointer::value, "" ); template struct is_pointer { static constexpr bool value = __is_pointer(T); }; static_assert( is_pointer::value, "" ); So the is_pointer template can still use the built-in even though the name '__is_pointer' has been declared as an identifier. So Clang matches GCC and it works fine. Good! >+ { >+ enum { __value = _IsPtr }; >+ }; >+#else > template > struct __is_pointer > { >@@ -377,6 +384,28 @@ __INT_N(__GLIBCXX_TYPE_INT_N_3) > typedef __true_type __type; > }; > >+ template >+ struct __is_pointer<_Tp* const> None of the other traits in bits/cpp_type_traits.h is true for cv-qualified types, so these partial specializations make __is_pointer the odd one out. Are they necessary? >+ { >+ enum { __value = 1 }; >+ typedef __true_type __type; >+ }; >+ >+ template >+ struct __is_pointer<_Tp* volatile> >+ { >+ enum { __value = 1 }; >+ typedef __true_type __type; >+ }; >+ >+ template >+ struct __is_pointer<_Tp* const volatile> >+ { >+ enum { __value = 1 }; >+ typedef __true_type __type; >+ }; >+#endif >+ > // > // An arithmetic type is an integer type or a floating point type > // >@@ -387,7 +416,7 @@ __INT_N(__GLIBCXX_TYPE_INT_N_3) > > // > // A scalar type is an arithmetic type or a pointer type >- // >+ // > template > struct __is_scalar > : public __traitor<__is_arithmetic<_Tp>, __is_pointer<_Tp> > >diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits >index 748fa186881..ea013b4b7bc 100644 >--- a/libstdc++-v3/include/std/type_traits >+++ b/libstdc++-v3/include/std/type_traits >@@ -542,19 +542,33 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION > : public true_type { }; > #endif > >- template >- struct __is_pointer_helper >+ /// is_pointer >+#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_pointer) >+ template >+ struct is_pointer >+ : public __bool_constant<__is_pointer(_Tp)> >+ { }; >+#else >+ template >+ struct is_pointer > : public false_type { }; > > template >- struct __is_pointer_helper<_Tp*> >+ struct is_pointer<_Tp*> > : public true_type { }; > >- /// is_pointer > template >- struct is_pointer >- : public __is_pointer_helper<__remove_cv_t<_Tp>>::type >- { }; >+ struct is_pointer<_Tp* const> >+ : public true_type { }; >+ >+ template >+ struct is_pointer<_Tp* volatile> >+ : public true_type { }; >+ >+ template >+ struct is_pointer<_Tp* const volatile> >+ : public true_type { }; >+#endif > > /// is_lvalue_reference > template >@@ -3268,8 +3282,22 @@ template > inline constexpr bool is_array_v<_Tp[_Num]> = true; > #endif > >+#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_pointer) >+template >+ inline constexpr bool is_pointer_v = __is_pointer(_Tp); >+#else > template >- inline constexpr bool is_pointer_v = is_pointer<_Tp>::value; >+ inline constexpr bool is_pointer_v = false; >+template >+ inline constexpr bool is_pointer_v<_Tp*> = true; >+template >+ inline constexpr bool is_pointer_v<_Tp* const> = true; >+template >+ inline constexpr bool is_pointer_v<_Tp* volatile> = true; >+template >+ inline constexpr bool is_pointer_v<_Tp* const volatile> = true; >+#endif >+ > template > inline constexpr bool is_lvalue_reference_v = false; > template >-- >2.44.0 >