From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 2181) id 5244F386186A; Mon, 7 Sep 2020 19:12:22 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 5244F386186A DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1599505942; bh=m5jCVTtqn+bnpDDfsSTUXivMsmewKIt6/AbHzPaTiP8=; h=From:To:Subject:Date:From; b=MwTaJ8VNwzS9TlhhxoBYcXwbnkAfhwxku+Bor6fS93tMJVRlZ6BxHrxdBPwuSIHBN VgTBs3HUpqGbnysvgs6wMEvrLKI+LB/Cj1HVzRAjrw3dIXj3UORSnhCk5EjfRxuBPD 3hcWruzKpYxW9YxKnubLaaIyzUiCueUqqYPfGHzw= Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit From: Jonathan Wakely To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r11-3040] libstdc++: Simplify chrono::duration::_S_gcd X-Act-Checkin: gcc X-Git-Author: Jonathan Wakely X-Git-Refname: refs/heads/master X-Git-Oldrev: 00ffe730072f5e2e1923692163dc37db7b3784cb X-Git-Newrev: ec5096f48bbd7db83cbe94bdd3235c5808a5979a Message-Id: <20200907191222.5244F386186A@sourceware.org> Date: Mon, 7 Sep 2020 19:12:22 +0000 (GMT) X-BeenThere: libstdc++-cvs@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libstdc++-cvs mailing list List-Unsubscribe: , List-Archive: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 07 Sep 2020 19:12:22 -0000 https://gcc.gnu.org/g:ec5096f48bbd7db83cbe94bdd3235c5808a5979a commit r11-3040-gec5096f48bbd7db83cbe94bdd3235c5808a5979a Author: Jonathan Wakely Date: Mon Sep 7 20:09:17 2020 +0100 libstdc++: Simplify chrono::duration::_S_gcd We can simplify this constexpr function further because we know that period::num >= 1 and period::den >= 1 so only the remainder can ever be zero. libstdc++-v3/ChangeLog: * include/std/chrono (duration::_S_gcd): Use invariant that neither value is zero initially. Diff: --- libstdc++-v3/include/std/chrono | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/libstdc++-v3/include/std/chrono b/libstdc++-v3/include/std/chrono index 0e2efb2522b..afee7859c6d 100644 --- a/libstdc++-v3/include/std/chrono +++ b/libstdc++-v3/include/std/chrono @@ -430,17 +430,18 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // Duration only allows positive periods so we don't need to // handle negative values here (unlike __static_gcd and std::gcd). #if __cplusplus >= 201402L - while (__m != 0 && __n != 0) + do { intmax_t __rem = __m % __n; __m = __n; __n = __rem; } - return __m + __n; + while (__n != 0); + return __m; #else // C++11 doesn't allow loops in constexpr functions, but this // recursive version can be more expensive to evaluate. - return (__m == 0) ? __n : (__n == 0) ? __m : _S_gcd(__n, __m % __n); + return (__n == 0) ? __m : _S_gcd(__n, __m % __n); #endif }