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[2001:8b0:1d0::2]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38c2a176449sm10925329f8f.11.2025.01.27.03.27.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 27 Jan 2025 03:27:16 -0800 (PST) From: Peter Maydell To: qemu-arm@nongnu.org, qemu-devel@nongnu.org Subject: [PATCH 0/2] target/arm: Deprecate iwMMXt emulation and associated CPUs Date: Mon, 27 Jan 2025 11:27:13 +0000 Message-Id: <20250127112715.2936555-1-peter.maydell@linaro.org> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Received-SPF: pass client-ip=2a00:1450:4864:20::42d; envelope-from=peter.maydell@linaro.org; helo=mail-wr1-x42d.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+patch=linaro.org@nongnu.org Sender: qemu-devel-bounces+patch=linaro.org@nongnu.org This patchset marks all the CPUs that support iwMMXt as deprecated, because I don't believe anybody is using them, and we have no way to test the thousands of lines of code we have that's only there for iwMMXt emulation. (See for instance the recent thread where a patch was submitted to fix an issue detected by a static analyzer: we didn't take it, largely because we had no way to know if the behaviour change the patch would produce was correct or not.) The pxa2xx CPUs are now only useful with user-mode emulation, because we dropped all the machine types that used them in 9.2. (Technically you could alse use "-cpu pxa270" with a board model like versatilepb which doesn't sanity-check the CPU type, but that has never been a supported config.) To use them (or iwMMXt emulation) with QEMU user-mode you would need to explicitly select them with the -cpu option or the QEMU_CPU environment variable, because the '-cpu max' default CPU does not include iwMMXt emulation. A google search finds no examples of anybody doing this in the last decade. I asked some of the Linaro GCC folks if they were using QEMU to test their iwMMXt codegen, or knew anybody doing that upstream, and the answer was "no". In fact, GCC is in the process of dropping support for iwMMXt entirely. We have one test case in check-tcg which purports to be checking iwMMXt. In fact it is doing no such thing: it runs the test without selecting an iwMMXt CPU, which means the iwMMXt insns are interpreted as FPA11 insns by the linux-user emulate_arm_fpa11() code. So the test prints garbage and then succeeds anyway. Modern distro toolchains can't generate a binary that will run with -cpu pxa270 (because their crt startup code uses Thumb insns); rather than putting in a lot of effort trying to salvage the test case to really test a feature we've deprecated, I opted to just remove the test. -- PMM Peter Maydell (2): target/arm: deprecate the pxa2xx CPUs and iwMMXt emulation tests/tcg/arm: Remove test-arm-iwmmxt test docs/about/deprecated.rst | 21 ++++++++++++++ target/arm/cpu.h | 1 + target/arm/cpu.c | 3 ++ target/arm/tcg/cpu32.c | 36 ++++++++++++++++-------- tests/tcg/arm/Makefile.target | 7 ----- tests/tcg/arm/README | 5 ---- tests/tcg/arm/test-arm-iwmmxt.S | 49 --------------------------------- 7 files changed, 49 insertions(+), 73 deletions(-) delete mode 100644 tests/tcg/arm/test-arm-iwmmxt.S Reviewed-by: Richard Henderson Reviewed-by: Philippe Mathieu-Daudé