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[189.204.159.168]) by smtp.gmail.com with ESMTPSA id f34sm419143otb.34.2020.12.01.07.09.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 01 Dec 2020 07:09:31 -0800 (PST) Subject: Re: [PATCH v2 20/28] target/arm: Implement new v8.1M VLLDM and VLSTM encodings To: Peter Maydell , qemu-arm@nongnu.org, qemu-devel@nongnu.org References: <20201119215617.29887-1-peter.maydell@linaro.org> <20201119215617.29887-21-peter.maydell@linaro.org> From: Richard Henderson Message-ID: <1a20d1c0-7734-edb4-8078-ab18d2834cb3@linaro.org> Date: Tue, 1 Dec 2020 09:09:28 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20201119215617.29887-21-peter.maydell@linaro.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2607:f8b0:4864:20::243; envelope-from=richard.henderson@linaro.org; helo=mail-oi1-x243.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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 11/19/20 3:56 PM, Peter Maydell wrote: > v8.1M adds new encodings of VLLDM and VLSTM (where bit 7 is set). > The only difference is that: > * the old T1 encodings UNDEF if the implementation implements 32 > Dregs (this is currently architecturally impossible for M-profile) > * the new T2 encodings have the implementation-defined option to > read from memory (discarding the data) or write UNKNOWN values to > memory for the stack slots that would be D16-D31 > > We choose not to make those accesses, so for us the two > instructions behave identically assuming they don't UNDEF. > > Signed-off-by: Peter Maydell > --- > target/arm/m-nocp.decode | 2 +- > target/arm/translate-vfp.c.inc | 25 +++++++++++++++++++++++++ > 2 files changed, 26 insertions(+), 1 deletion(-) Reviewed-by: Richard Henderson r~