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[88.10.103.234]) by smtp.gmail.com with ESMTPSA id u8sm2087372wmj.45.2020.09.25.02.22.21 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 25 Sep 2020 02:22:21 -0700 (PDT) Subject: Re: [PATCH 4/4] qemu/bswap: Remove dependency To: Peter Maydell , Richard Henderson References: <20200923100220.674903-1-philmd@redhat.com> <20200923100220.674903-5-philmd@redhat.com> <2a2cc60d-2d30-eb38-369e-0a26f0eac9bd@linaro.org> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Autocrypt: addr=philmd@redhat.com; keydata= mQINBDXML8YBEADXCtUkDBKQvNsQA7sDpw6YLE/1tKHwm24A1au9Hfy/OFmkpzo+MD+dYc+7 bvnqWAeGweq2SDq8zbzFZ1gJBd6+e5v1a/UrTxvwBk51yEkadrpRbi+r2bDpTJwXc/uEtYAB GvsTZMtiQVA4kRID1KCdgLa3zztPLCj5H1VZhqZsiGvXa/nMIlhvacRXdbgllPPJ72cLUkXf z1Zu4AkEKpccZaJspmLWGSzGu6UTZ7UfVeR2Hcc2KI9oZB1qthmZ1+PZyGZ/Dy+z+zklC0xl XIpQPmnfy9+/1hj1LzJ+pe3HzEodtlVA+rdttSvA6nmHKIt8Ul6b/h1DFTmUT1lN1WbAGxmg CH1O26cz5nTrzdjoqC/b8PpZiT0kO5MKKgiu5S4PRIxW2+RA4H9nq7nztNZ1Y39bDpzwE5Sp bDHzd5owmLxMLZAINtCtQuRbSOcMjZlg4zohA9TQP9krGIk+qTR+H4CV22sWldSkVtsoTaA2 qNeSJhfHQY0TyQvFbqRsSNIe2gTDzzEQ8itsmdHHE/yzhcCVvlUzXhAT6pIN0OT+cdsTTfif MIcDboys92auTuJ7U+4jWF1+WUaJ8gDL69ThAsu7mGDBbm80P3vvUZ4fQM14NkxOnuGRrJxO qjWNJ2ZUxgyHAh5TCxMLKWZoL5hpnvx3dF3Ti9HW2dsUUWICSQARAQABtDJQaGlsaXBwZSBN YXRoaWV1LURhdWTDqSAoUGhpbCkgPHBoaWxtZEByZWRoYXQuY29tPokCVQQTAQgAPwIbDwYL CQgHAwIGFQgCCQoLBBYCAwECHgECF4AWIQSJweePYB7obIZ0lcuio/1u3q3A3gUCXsfWwAUJ KtymWgAKCRCio/1u3q3A3ircD/9Vjh3aFNJ3uF3hddeoFg1H038wZr/xi8/rX27M1Vj2j9VH 0B8Olp4KUQw/hyO6kUxqkoojmzRpmzvlpZ0cUiZJo2bQIWnvScyHxFCv33kHe+YEIqoJlaQc JfKYlbCoubz+02E2A6bFD9+BvCY0LBbEj5POwyKGiDMjHKCGuzSuDRbCn0Mz4kCa7nFMF5Jv piC+JemRdiBd6102ThqgIsyGEBXuf1sy0QIVyXgaqr9O2b/0VoXpQId7yY7OJuYYxs7kQoXI 6WzSMpmuXGkmfxOgbc/L6YbzB0JOriX0iRClxu4dEUg8Bs2pNnr6huY2Ft+qb41RzCJvvMyu gS32LfN0bTZ6Qm2A8ayMtUQgnwZDSO23OKgQWZVglGliY3ezHZ6lVwC24Vjkmq/2yBSLakZE 6DZUjZzCW1nvtRK05ebyK6tofRsx8xB8pL/kcBb9nCuh70aLR+5cmE41X4O+MVJbwfP5s/RW 9BFSL3qgXuXso/3XuWTQjJJGgKhB6xXjMmb1J4q/h5IuVV4juv1Fem9sfmyrh+Wi5V1IzKI7 RPJ3KVb937eBgSENk53P0gUorwzUcO+ASEo3Z1cBKkJSPigDbeEjVfXQMzNt0oDRzpQqH2vp apo2jHnidWt8BsckuWZpxcZ9+/9obQ55DyVQHGiTN39hkETy3Emdnz1JVHTU0Q== Message-ID: <70564f81-d2a6-9bad-b761-40e0d5c69961@redhat.com> Date: Fri, 25 Sep 2020 11:22:20 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=philmd@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=philmd@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/25 02:48:20 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.199, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.214, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Alexander von Gluck IV , Ed Maste , QEMU Developers , Li-Wen Hsu Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 9/24/20 9:33 PM, Peter Maydell wrote: > On Thu, 24 Sep 2020 at 20:30, Richard Henderson > wrote: >> >> On 9/23/20 3:30 AM, Philippe Mathieu-Daudé wrote: >>> On 9/23/20 12:16 PM, Peter Maydell wrote: >>>> I suppose if we wanted to just use the __builtin_bswap* >>>> implementation on all hosts (ie drop the special casing >>>> of CONFIG_MACHINE_BSWAP_H/FreeBSD/Haiku) we'd need to >>>> rename our macros to avoid potential conflicts with the >>>> versions in the system headers there in case they were >>>> pulled in via some other path ? >>> >>> Yes, this is why I couldn't get ride of everything >>> >>> After reading Paolo's suggestion to use qatomic*, I >>> am tempted to suggest qbswap* but I am still looking >>> for better alternatives... >> >> Hum, maybe. It's pretty ugly. We could just leave those alone and hope the >> system version is decent enough. > > Mostly what I would like is to be able to be rid of the > configure machinery so we could just use a single > portable implementation. Good news. Using the Haiku image provided by Alexander, GCC is pretty recent and supports builtin atomic: > uname -a Haiku shredder 1 hrev54154+115 Jun 30 2020 15:20 x86_64 x86_64 Haiku > gcc --version gcc (2019_05_24) 8.3.0 Copyright (C) 2018 Free Software Foundation, Inc. The include (/system/develop/headers/posix/endian.h) only defines BYTE_ORDER. Looking at FreeBSD, bswap*() are defined as macro: https://github.com/freebsd/freebsd/blob/master/sys/sys/endian.h#L58 So we could eventually undefine them... but the manpage describe them as functions [*]: DESCRIPTION The bswap16(), bswap32(), and bswap64() functions return a byte order swapped integer. So theoretically they could change the prototype still respecting the documentation contract, and undefines wouldn't work anymore. Would this be acceptable? Any clever idea? [*] https://www.freebsd.org/cgi/man.cgi?query=bswap32&apropos=0&sektion=9 > > thanks > -- PMM >