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Tue, 26 Jan 2021 09:10:40 -0800 (PST) Received: from zen.linaroharston ([51.148.130.216]) by smtp.gmail.com with ESMTPSA id j2sm26417595wrh.78.2021.01.26.09.10.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 26 Jan 2021 09:10:39 -0800 (PST) Received: from zen (localhost [127.0.0.1]) by zen.linaroharston (Postfix) with ESMTP id 41AA31FF7E; Tue, 26 Jan 2021 17:10:38 +0000 (GMT) References: <20210110162739.858087-1-f4bug@amsat.org> <20210110162739.858087-3-f4bug@amsat.org> <78a9718b-dec0-cc31-7ada-e815d9022e65@redhat.com> <20210121103250.GH3125227@redhat.com> <20210121112154.GJ3125227@redhat.com> <20210121120241.GK3125227@redhat.com> <97b12e1b-e570-bd4d-5484-376f3fe6f7dc@amsat.org> <7e423408-b0e9-2c32-b88b-eb579dd273c5@weilnetz.de> User-agent: mu4e 1.5.7; emacs 28.0.50 From: Alex =?utf-8?Q?Benn=C3=A9e?= To: Stefan Weil Subject: Re: [RFC PATCH 2/2] gitlab-ci: Add a job building TCI with Clang Date: Tue, 26 Jan 2021 17:08:30 +0000 In-reply-to: <7e423408-b0e9-2c32-b88b-eb579dd273c5@weilnetz.de> Message-ID: <878s8fy67l.fsf@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=2a00:1450:4864:20::433; envelope-from=alex.bennee@linaro.org; helo=mail-wr1-x433.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, 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: Thomas Huth , =?utf-8?Q?Daniel_P=2E_Berrang=C3=A9?= , Richard Henderson , Philippe =?utf-8?Q?Mathieu-Daud?= =?utf-8?Q?=C3=A9?= , Wataru Ashihara , qemu-devel@nongnu.org, Wainer dos Santos Moschetta , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Stefan Weil writes: > Am 23.01.21 um 09:59 schrieb Wataru Ashihara: > >> Actually I use TCI also on macOS. Like the use case quoted by Philippe, >> there're even other reasons to use TCI: >> >> 1. Learning TCG ops. >> 2. Debugging QEMU with gdb. e.g. diagnose codegen or stepping into >> helper functions from tci.c:tcg_qemu_tb_exec(). >> 3. Guest instruction tracing. TCI is faster than TCG or KVM when tracing >> the guest ops [1]. I guess qira is using TCI for this reason [2]. >> >> [1]: https://twitter.com/wata_ash/status/1352899988032942080 >> [2]: https://github.com/geohot/qira/blob/v1.3/tracers/qemu_build.sh#L55 > > > Yes, TCI can help a lot for debugging, especially also when porting TCG=20 > to a new host architecture. > > If we had binaries which can switch from native to interpreted TCG, it=20 > could also be a reference implementation used for unit tests, comparing=20 > the results for each TCG opcode. > > Using TCI with profiling like gprof is useful to count the frequency of=20 > the different TCG opcodes in practical scenarios and can be used to=20 > detect bottlenecks (and less frequent or unused opcodes) for native TCG,= =20 > too. FWIW I had a bunch of JIT profiling changes that exposed the TCG op counts via the JIT profiler. I think I even enabled the op counting by default because it was fairly lightweight to add. IOW I think more introspection can be brought into the core TCG code rather than relying on TCI to achieve it. --=20 Alex Benn=C3=A9e