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[174.21.72.5]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1f44c99461asm102177715ad.207.2024.05.29.10.39.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 29 May 2024 10:39:21 -0700 (PDT) Message-ID: <6ee29ed0-c893-4f16-8afb-55ff365b1f1e@linaro.org> Date: Wed, 29 May 2024 10:39:19 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 03/67] target/arm: Reject incorrect operands to PLD, PLDW, PLI To: Peter Maydell Cc: qemu-devel@nongnu.org, qemu-arm@nongnu.org References: <20240524232121.284515-1-richard.henderson@linaro.org> <20240524232121.284515-4-richard.henderson@linaro.org> <3f1baa61-c623-4b5b-b724-15bb68a2df3f@linaro.org> Content-Language: en-US From: Richard Henderson In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2607:f8b0:4864:20::634; envelope-from=richard.henderson@linaro.org; helo=mail-pl1-x634.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, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 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-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 5/29/24 06:32, Peter Maydell wrote: >> We do plenty of other treatments of UNPREDICTABLE as UNDEF (e.g. STREX). Why is this case >> any different? > > It just seems like a lot of effort to go to. Sometimes we > UNDEF for UNPREDICTABLEs, but quite often we say "the > behaviour we get for free is fine, so no need to write > extra code". > > In this particular case, also: > * we'd need to go back and cross-check against older > architecture manuals and also look at whether M-profile > and A-profile are doing the same thing here > * the "v8 loosens the UNPREDICTABLE case for m = 13 T1 > encoding" looks suspiciously to me like a "nobody ever > actually made this do anything except behave like the A1 > encoding, so make T1 and A1 the same" kind of relaxation > > Basically, it would take me probably 15+ minutes to review > the changes against the various versions of the docs and > I don't think it's worth the effort :-) Fair enough. I've sent a patch to update thumb.risu to avoid the problematic patterns. r~