From owner-svn-src-all@freebsd.org Sun May 29 20:02:54 2016 Return-Path: Delivered-To: svn-src-all@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 9C287B54025; Sun, 29 May 2016 20:02:54 +0000 (UTC) (envelope-from cse.cem@gmail.com) Received: from mail-it0-f54.google.com (mail-it0-f54.google.com [209.85.214.54]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 71CFB115D; Sun, 29 May 2016 20:02:54 +0000 (UTC) (envelope-from cse.cem@gmail.com) Received: by mail-it0-f54.google.com with SMTP id e62so24609610ita.1; Sun, 29 May 2016 13:02:54 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:reply-to:in-reply-to:references :date:message-id:subject:from:to:cc; bh=io04YlPYUKiX/BeNQuLhcbDEm4vbt0OdY3eI/AobXZQ=; b=FZRqMSE/Kumoti4uqtnyogCi/S04iPJczhGdQBvEqY17PJSgqOankRO9xd/Y398Uhk JY2AiAzoJZ5HibSmI8Xe616wBFryB/g+2brxrz971V6SHCYqHLQz+Q4hKJAkcIB8l6iX MNWjBUzizCSMnAfVIpzzVaMklI2V63/wlf66akL+s+5w7O4HWKrNTbrvTZqq9mZ7FuAK rf5qC7fxg+osAtq9dK+1LVUFPtjJs55PjhtFw5P6rhmssgnkyUYOwaBiFkJaWF74CIVJ +1uAzhZt7srE87Ax6WSvT5c87J1mppF4HgRJg33fKeaYa+UrgA64hDvxFFJ39w9RdQfY vQWA== X-Gm-Message-State: ALyK8tL41qkouzyNO5+OmxxZvogw1fIa8AlKPGvJuP5WSyi8zfZbvwEQrDD9WJxOhWk77A== X-Received: by 10.36.58.75 with SMTP id m72mr5303190itm.96.1464550774266; Sun, 29 May 2016 12:39:34 -0700 (PDT) Received: from mail-it0-f41.google.com (mail-it0-f41.google.com. [209.85.214.41]) by smtp.gmail.com with ESMTPSA id d74sm6045987ith.13.2016.05.29.12.39.33 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 29 May 2016 12:39:34 -0700 (PDT) Received: by mail-it0-f41.google.com with SMTP id z123so20190225itg.0; Sun, 29 May 2016 12:39:33 -0700 (PDT) MIME-Version: 1.0 X-Received: by 10.36.158.133 with SMTP id p127mr5273315itd.97.1464550773590; Sun, 29 May 2016 12:39:33 -0700 (PDT) Reply-To: cem@FreeBSD.org Received: by 10.36.205.70 with HTTP; Sun, 29 May 2016 12:39:33 -0700 (PDT) In-Reply-To: <201605291639.u4TGdSwq032144@repo.freebsd.org> References: <201605291639.u4TGdSwq032144@repo.freebsd.org> Date: Sun, 29 May 2016 12:39:33 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: svn commit: r300965 - head/lib/libc/stdlib From: Conrad Meyer To: "Andrey A. Chernov" Cc: src-committers , svn-src-all@freebsd.org, svn-src-head@freebsd.org Content-Type: text/plain; charset=UTF-8 X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 29 May 2016 20:02:54 -0000 Does clang actually generate different code with this change? On Sun, May 29, 2016 at 9:39 AM, Andrey A. Chernov wrote: > Author: ache > Date: Sun May 29 16:39:28 2016 > New Revision: 300965 > URL: https://svnweb.freebsd.org/changeset/base/300965 > > Log: > Micro optimize: C standard guarantees that right shift for unsigned value > fills left bits with zero, and we have exact 32bit unsigned value > (uint32_t), so there is no reason to add "& 0x7fffffff" here. > > MFC after: 1 week > > Modified: > head/lib/libc/stdlib/random.c > > Modified: head/lib/libc/stdlib/random.c > ============================================================================== > --- head/lib/libc/stdlib/random.c Sun May 29 16:32:56 2016 (r300964) > +++ head/lib/libc/stdlib/random.c Sun May 29 16:39:28 2016 (r300965) > @@ -430,7 +430,7 @@ random(void) > */ > f = fptr; r = rptr; > *f += *r; > - i = (*f >> 1) & 0x7fffffff; /* chucking least random bit */ > + i = *f >> 1; /* chucking least random bit */ > if (++f >= end_ptr) { > f = state; > ++r; >