From owner-freebsd-emulation@freebsd.org Wed Mar 4 11:27:19 2020 Return-Path: Delivered-To: freebsd-emulation@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 1901626C1D0 for ; Wed, 4 Mar 2020 11:27:19 +0000 (UTC) (envelope-from madpilot@FreeBSD.org) Received: from mailman.nyi.freebsd.org (mailman.nyi.freebsd.org [IPv6:2610:1c1:1:606c::50:13]) by mx1.freebsd.org (Postfix) with ESMTP id 48XWnJ3n5Rz3NZ1 for ; Wed, 4 Mar 2020 11:27:16 +0000 (UTC) (envelope-from madpilot@FreeBSD.org) Received: by mailman.nyi.freebsd.org (Postfix) id AB1C426C1C7; Wed, 4 Mar 2020 11:27:15 +0000 (UTC) Delivered-To: emulation@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 AA45526C1C6 for ; Wed, 4 Mar 2020 11:27:15 +0000 (UTC) (envelope-from madpilot@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 48XWnH2rN4z3NY3 for ; Wed, 4 Mar 2020 11:27:15 +0000 (UTC) (envelope-from madpilot@FreeBSD.org) Received: by freefall.freebsd.org (Postfix) id 3B82916AA3; Wed, 4 Mar 2020 11:27:14 +0000 (UTC) Delivered-To: vbox@localmail.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) client-signature RSA-PSS (4096 bits)) (Client CN "mx1.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by freefall.freebsd.org (Postfix) with ESMTPS id 07AA0168FE; Wed, 4 Mar 2020 11:27:14 +0000 (UTC) (envelope-from madpilot@FreeBSD.org) Received: from smtp.freebsd.org (smtp.freebsd.org [IPv6:2610:1c1:1:606c::24b:4]) (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 "smtp.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 48XWnF1TFLz3NX3; Wed, 4 Mar 2020 11:27:13 +0000 (UTC) (envelope-from madpilot@FreeBSD.org) Received: from marvin.madpilot.net (host146-240-dynamic.10-87-r.retail.telecomitalia.it [87.10.240.146]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client did not present a certificate) (Authenticated sender: madpilot/mail) by smtp.freebsd.org (Postfix) with ESMTPSA id 11BD110741; Wed, 4 Mar 2020 11:27:11 +0000 (UTC) (envelope-from madpilot@FreeBSD.org) Subject: Re: svn commit: r358439 - head/sys/amd64/include To: Ryan Libby , "Alexander V. Chernikov" Cc: "svn-src-head@freebsd.org" , "svn-src-all@freebsd.org" , "src-committers@freebsd.org" , vbox@FreeBSD.org References: <202002281832.01SIWaEL071685@repo.freebsd.org> <5767791583138727@sas1-c7aad230fe87.qloud-c.yandex.net> From: Guido Falsi Message-ID: <3d54ebc3-a511-a239-136d-c0f638a69351@FreeBSD.org> Date: Wed, 4 Mar 2020 12:27:08 +0100 User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Mailman-Approved-At: Wed, 04 Mar 2020 14:07:28 +0000 X-BeenThere: freebsd-emulation@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Development of Emulators of other operating systems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 04 Mar 2020 11:27:19 -0000 On 02/03/20 18:13, Ryan Libby wrote: > On Mon, Mar 2, 2020 at 12:45 AM Alexander V. Chernikov wrote: >> >> 28.02.2020, 18:32, "Ryan Libby" : >>> Author: rlibby >>> Date: Fri Feb 28 18:32:36 2020 >>> New Revision: 358439 >>> URL: https://svnweb.freebsd.org/changeset/base/358439 >>> >>> Log: >>> amd64 atomic.h: minor codegen optimization in flag access >>> >>> Previously the pattern to extract status flags from inline assembly >>> blocks was to use setcc in the block to write the flag to a register. >>> This was suboptimal in a few ways: >>> - It would lead to code like: sete %cl; test %cl; jne, i.e. a flag >>> would just be loaded into a register and then reloaded to a flag. >>> - The setcc would force the block to use an additional register. >>> - If the client code didn't care for the flag value then the setcc >>> would be entirely pointless but could not be eliminated by the >>> optimizer. >>> >>> A more modern inline asm construct (since gcc 6 and clang 9) allows for >> This effectively restricts kernel builds by all older compilers. >> Is there any chance of making it conditional depending on the compiler version/features? > > Yes, it is possible to test for __GCC_ASM_FLAG_OUTPUTS__. It is more > maintenance effort going forward. If building current with an old cross > compiler is an important scenario, we can either revert this and the > following revision or work up a patch to make it conditional. I'll see > what that might look like. > Actually this causes emulators/virtualbox-ose port to fail to build: In file included from /usr/src/sys/sys/systm.h:44: /usr/include/machine/atomic.h:230:1: error: invalid output constraint '=@cce' in asm ATOMIC_CMPSET(char); ^ /usr/include/machine/atomic.h:205:4: note: expanded from macro 'ATOMIC_CMPSET' : "=@cce" (res), /* 0 */ \ ^ /usr/include/machine/atomic.h:230:1: error: invalid output constraint '=@cce' in asm (and so on) the virtualbox-ose port is forced to use an older clang version due to crashes when compiled with newer ones. Not sure whose responsibility is to fix this. Should I file a bug report on bugzilla? -- Guido Falsi