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[174.21.70.228]) by smtp.gmail.com with ESMTPSA id r5sm5656886pjd.2.2021.06.09.10.09.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 09 Jun 2021 10:09:31 -0700 (PDT) Subject: Re: [PATCH 11/55] target/arm: Implement MVE VLDR/VSTR (non-widening forms) To: Peter Maydell References: <20210607165821.9892-1-peter.maydell@linaro.org> <20210607165821.9892-12-peter.maydell@linaro.org> From: Richard Henderson Message-ID: <7f4f43cf-2a9b-d08a-90f5-46f4f307b5f5@linaro.org> Date: Wed, 9 Jun 2021 10:09:29 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 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::534; envelope-from=richard.henderson@linaro.org; helo=mail-pg1-x534.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=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: qemu-arm , QEMU Developers Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 6/9/21 3:01 AM, Peter Maydell wrote: >> Is the spec forward looking to more than 7 Q registers? >> It's tempting to just drop the D:Qd from the decode... > > I don't know, but looking at the decode it certainly seems > like the door is being left open to Q8..Q15. Other signs of > this include the existence of the VFPSmallRegisterBank() > function and the way that VLLDM and VLSTM have T2 encodings > whose only difference from the T1 encodings is that you can > specify registers up to D31. Decoding D:Qd and then doing the > range check seemed more in line with the spirit of this... I agree. We should leave the decode in place. Do you think it's worthwhile adding a single hook for the register range check now? E.g. if (!mve_check_qreg_bank(s, a->qd | a->qn | a->qm)) { return false; } static bool mve_check_qreg_bank(DisasContext *s, int qmask) { /* * See VFPSmallRegisterBank, always true for armv8.1-m. * So only Q0...Q7 are supported. */ return qmask < 8; } And, as needed, another one for dregs. r~