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[174.21.143.238]) by smtp.gmail.com with ESMTPSA id x77sm3468469pfc.4.2020.06.18.09.12.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 18 Jun 2020 09:12:43 -0700 (PDT) Subject: Re: [PATCH v7 10/42] target/arm: Implement the ADDG, SUBG instructions To: Peter Maydell References: <20200603011317.473934-1-richard.henderson@linaro.org> <20200603011317.473934-11-richard.henderson@linaro.org> From: Richard Henderson Message-ID: <3b1b50b8-061e-8422-2df0-e8df6f856941@linaro.org> Date: Thu, 18 Jun 2020 09:12:40 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2607:f8b0:4864:20::444; envelope-from=richard.henderson@linaro.org; helo=mail-pf1-x444.google.com X-detected-operating-system: by eggs.gnu.org: No matching host in p0f cache. That's all we know. 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=_AUTOLEARN 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 , Stephen Long Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 6/18/20 6:17 AM, Peter Maydell wrote: >> + imm = (imm >> 6) << LOG2_TAG_GRANULE; ... >> + TCGv_i32 tag_offset = tcg_const_i32(imm & 15); ... > Given that we don't really share any of the codegen with the > existing disas_add_sub_imm() insns, and the insn format isn't > the same (uimm6/op3/uimm4 rather than an imm12), I'm tempted > to suggest we should structure this the same way the Arm ARM > decode tables do, where "Add/subtract (immediate, with tags)" > is a separate subtable from "Add/subtract (immediate)": so > instead of disas_data_proc_imm() sending both case > 0x22 and 0x23 to disas_add_sub_imm(), it would send 0x23 > to a new disas_add_sub_tag(). I'll do that, because... > But this patch is functionally correct... ... I've just noticed that it isn't correct. I drop the low 6 bits of the 12-bit "imm" on the first line, and then try to read the low 4 bits on the second line. Oops. r~