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 690B5388216D for ; Thu, 17 Aug 2023 20:32:30 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 690B5388216D Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1692304350; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=2GAyMKZBPO2azSOE2IuTUTRZu109rMIvVYAQPUh6iYg=; b=QQFwqzGOgYC+SMbpIyVbvGAaX/eKij0C5oDYhzqfOF65SmRft2BTZnrcf8KtnZDcoZpq8B jnM4OvDN3aW2X7uRbxQvrgf9EPsZogw8tGegMjFernpl1pldB4z0oV+XNB6/IBOq8cbeor F8mwD3qttdlK53QvFbh+EAmcQc37RmY= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-223-uFbNvMmSPXCDjpeIP55ZcA-1; Thu, 17 Aug 2023 16:32:28 -0400 X-MC-Unique: uFbNvMmSPXCDjpeIP55ZcA-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 6D8438DC66B; Thu, 17 Aug 2023 20:32:28 +0000 (UTC) Received: from localhost (unknown [10.42.28.201]) by smtp.corp.redhat.com (Postfix) with ESMTP id 364FA1121314; Thu, 17 Aug 2023 20:32:28 +0000 (UTC) From: Jonathan Wakely To: libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org Subject: [committed] libstdc++: Micro-optimize construction of named std::locale Date: Thu, 17 Aug 2023 21:32:24 +0100 Message-ID: <20230817203228.1131577-1-jwakely@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-11.8 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,SPF_HELO_NONE,SPF_NONE,TXREP 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: Tested x86_64-linux. Pushed to trunk. -- >8 -- This shaves about 100ns off the std::locale constructor for named locales (which is only about 1% of the total time). Using !*s instead of !strcmp(s, "") doesn't make any difference as GCC optimizes that already even at -O1. !strcmp(s, "C") is optimized at -O2 so replacing that with s[0] == 'C' && s[1] == '\0' only matters for the --enable-libstdcxx-debug builds. But !strcmp(s, "POSIX") always makes a call to strcmp at any optimization level. We make that strcmp call, maybe several times, for any locale name except for "C" (which will be matched before we get to the check for "POSIX"). For most targets, locale names begin with a lowercase letter and the only one that begins with 'P' is "POSIX". Replacing !strcmp(s, "POSIX") with s[0] == 'P' && !strcmp(s+1, "OSIX") means that we avoid calling strcmp unless the string really does match "POSIX". Maybe more importantly, I find is_C_locale(s) easier to read than strcmp(s, "C") == 0 || strcmp(s, "POSIX") == 0, and !is_C_locale(s) easier to read than strcmp(s, "C") != 0 && strcmp(s, "POSIX") != 0. libstdc++-v3/ChangeLog: * src/c++98/localename.cc (is_C_locale): New function. (locale::locale(const char*)): Use is_C_locale. --- libstdc++-v3/src/c++98/localename.cc | 39 ++++++++++++++++------------ 1 file changed, 23 insertions(+), 16 deletions(-) diff --git a/libstdc++-v3/src/c++98/localename.cc b/libstdc++-v3/src/c++98/localename.cc index 25e6d966dca..68cb81d0709 100644 --- a/libstdc++-v3/src/c++98/localename.cc +++ b/libstdc++-v3/src/c++98/localename.cc @@ -36,24 +36,37 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION using namespace __gnu_cxx; + static inline bool + is_C_locale(const char* s) + { + switch (s[0]) + { + case 'C': + return s[1] == '\0'; + case 'P': + return !std::strcmp(s+1, "OSIX"); + default: + return false; + } + } + locale::locale(const char* __s) : _M_impl(0) { if (__s) { _S_initialize(); - if (std::strcmp(__s, "C") == 0 || std::strcmp(__s, "POSIX") == 0) + if (is_C_locale(__s)) (_M_impl = _S_classic)->_M_add_reference(); - else if (std::strcmp(__s, "") != 0) + else if (*__s) _M_impl = new _Impl(__s, 1); else { // Get it from the environment. char* __env = std::getenv("LC_ALL"); // If LC_ALL is set we are done. - if (__env && std::strcmp(__env, "") != 0) + if (__env && *__env) { - if (std::strcmp(__env, "C") == 0 - || std::strcmp(__env, "POSIX") == 0) + if (is_C_locale(__env)) (_M_impl = _S_classic)->_M_add_reference(); else _M_impl = new _Impl(__env, 1); @@ -63,9 +76,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // LANG may set a default different from "C". string __lang; __env = std::getenv("LANG"); - if (!__env || std::strcmp(__env, "") == 0 - || std::strcmp(__env, "C") == 0 - || std::strcmp(__env, "POSIX") == 0) + if (!__env || !*__env || is_C_locale(__env)) __lang = "C"; else __lang = __env; @@ -77,17 +88,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION for (; __i < _S_categories_size; ++__i) { __env = std::getenv(_S_categories[__i]); - if (__env && std::strcmp(__env, "") != 0 - && std::strcmp(__env, "C") != 0 - && std::strcmp(__env, "POSIX") != 0) + if (__env && *__env && !is_C_locale(__env)) break; } else for (; __i < _S_categories_size; ++__i) { __env = std::getenv(_S_categories[__i]); - if (__env && std::strcmp(__env, "") != 0 - && __lang != __env) + if (__env && *__env && __lang != __env) break; } @@ -113,14 +121,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { __env = std::getenv(_S_categories[__i]); __str += _S_categories[__i]; - if (!__env || std::strcmp(__env, "") == 0) + if (!__env || !*__env) { __str += '='; __str += __lang; __str += ';'; } - else if (std::strcmp(__env, "C") == 0 - || std::strcmp(__env, "POSIX") == 0) + else if (is_C_locale(__env)) __str += "=C;"; else { -- 2.41.0