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Thu, 08 Jul 2021 09:17:36 -0700 (PDT) Received: from [192.168.1.11] ([71.212.149.176]) by smtp.gmail.com with ESMTPSA id g10sm9908263pji.10.2021.07.08.09.17.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 08 Jul 2021 09:17:36 -0700 (PDT) Subject: Re: [PATCH v2 05/28] target/arm: Use gen_jmp for ISB and SB To: Peter Maydell References: <20210630183226.3290849-1-richard.henderson@linaro.org> <20210630183226.3290849-6-richard.henderson@linaro.org> <88562e08-3d6c-3224-5d84-67e3ffd3774b@linaro.org> From: Richard Henderson Message-ID: <589d27e5-58e5-6af2-dfd8-11130fdbc2d9@linaro.org> Date: Thu, 8 Jul 2021 09:17:34 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2607:f8b0:4864:20::52a; envelope-from=richard.henderson@linaro.org; helo=mail-pg1-x52a.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, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable 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: qemu-arm , QEMU Developers Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 7/8/21 9:11 AM, Peter Maydell wrote: >>> Why isn't it enough here just to set is_jmp to DISAS_NEXT ? >> >> You mean DISAS_TOO_MANY? That would work, yes. >> At the time I was just thinking of replacing one jump with another. > > You've implicitly answered my question, which is that the main > translator loop code treats DISAS_NEXT as "keep adding insns to > the TB" :-) > > It feels slightly like misuse to use DISAS_TOO_MANY, unless we > renamed it to something like DISAS_END_TB (which is what it's > actually doing). Yeah, better naming would have been a good. In this instance I think I chose an odd colour for the bike shed. The problem with just DISAS_END_TB is that there are many ways to end a tb, with at least: (1) goto_tb next, (2) goto_ptr next, (3) exit_tb. We wind up replicating these three across many of the targets, so it would be a really nice cleanup to standardize, and with good names. r~