From owner-svn-src-all@freebsd.org Thu Oct 24 15:34:33 2019 Return-Path: Delivered-To: svn-src-all@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id C70C816FD62; Thu, 24 Oct 2019 15:34:33 +0000 (UTC) (envelope-from danfe@freebsd.org) Received: from freefall.freebsd.org (freefall.freebsd.org [96.47.72.132]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) server-signature RSA-PSS (4096 bits) client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "freefall.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 46zWWY4sD6z3Pl2; Thu, 24 Oct 2019 15:34:33 +0000 (UTC) (envelope-from danfe@freebsd.org) Received: by freefall.freebsd.org (Postfix, from userid 1033) id 9F36CF2D5; Thu, 24 Oct 2019 15:34:33 +0000 (UTC) Date: Thu, 24 Oct 2019 15:34:33 +0000 From: Alexey Dokuchaev To: Warner Losh Cc: Dimitry Andric , src-committers , svn-src-all , svn-src-head Subject: Re: svn commit: r353936 - head/contrib/llvm/tools/clang/lib/Driver/ToolChains/Arch Message-ID: <20191024153433.GA68256@FreeBSD.org> References: <201910231657.x9NGvCMD039111@repo.freebsd.org> <20191024082609.GA63459@FreeBSD.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.4 (2019-03-13) X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.29 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: Thu, 24 Oct 2019 15:34:33 -0000 On Thu, Oct 24, 2019 at 09:14:07AM -0600, Warner Losh wrote: > On Thu, Oct 24, 2019 at 2:26 AM Alexey Dokuchaev wrote: > > On Wed, Oct 23, 2019 at 04:57:12PM +0000, Dimitry Andric wrote: > > > New Revision: 353936 > > > URL: https://svnweb.freebsd.org/changeset/base/353936 > > > > > > Log: > > > Bump clang's default target CPU for the i386 architecture (aka > > > "x86") to i686, as per the discussion on the freebsd-arch mailing > > > list. > > > > Why i686, not i586? i486 lacking 64-bit atomics is a sound and valid > > reason, but I don't understand why i586 wasn't chosen, and quick review > > of that -arch thread did not help. > > There were several notions at play here. First, the rest of the i386 > ecosystem has defaulted to i686 for a long time. [...] > > i686 support by default allows better code generation and increased > performance. The biggest thing being using CMOVxx instructions to avoid > a pipeline miss due to branching, though there's likely others. > > By moving to i686 by default, we have only one bump instead of two. [...] > > So that's where we are: a mix of technical and political reasons were why > we bumped up to i686 by default Understood. I appreciate long and elaborate reply Warner. > Chances are this will be the last minimum bump as well before i386 is > removed from the tree as irrelevant (some years from now, but the day > will come). I hope the day never comes, as I don't want to be forced from FreeBSD to something else on vast majority of my hardware. ./danfe