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Thu, 11 Jul 2019 13:55:33 -0700 (PDT) MIME-Version: 1.0 References: <20190710130206.1670830-1-arnd@arndb.de> <33511b0e-6d7b-c156-c415-7a609b049567@arm.com> In-Reply-To: From: Arnd Bergmann Date: Thu, 11 Jul 2019 22:55:16 +0200 Message-ID: Subject: Re: [PATCH] vsyscall: use __iter_div_u64_rem() To: Nick Desaulniers X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190711_135535_852873_B7DCA0CA X-CRM114-Status: GOOD ( 10.97 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch , Shuah Khan , Linux Kernel Mailing List , "open list:KERNEL SELFTEST FRAMEWORK" , Dmitry Safonov <0x7f454c46@gmail.com>, Mark Salyzyn , Huw Davies , Catalin Marinas , Daniel Lezcano , Will Deacon , linux-mips@vger.kernel.org, Ralf Baechle , Russell King , clang-built-linux , Paul Burton , Andy Lutomirski , Rasmus Villemoes , Thomas Gleixner , Vincenzo Frascino , Peter Collingbourne , Linux ARM Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Jul 11, 2019 at 7:14 PM 'Nick Desaulniers' via Clang Built Linux wrote: > > On Thu, Jul 11, 2019 at 5:28 AM Arnd Bergmann wrote: > > clang does not like an inline assembly with a "=q" contraint for > > a 64-bit output: > > Seems like starting in GCC 7, GCC may not like it either: > https://godbolt.org/z/UyBUfh > it simply warns then proceeds with code gen. Another difference may > come from when GCC vs Clang perform dead code elimination (DCE) vs > semantic analysis. Right, I also had the idea to work around it with a set of __builtin_choos_expr() instead of the switch()/case but did not complete that patch as the percpu code is rather complex and this would touch lots of code. Arnd _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel