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Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:48304) by pandora.armlinux.org.uk with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jMyU0-0002yv-1a; Fri, 10 Apr 2020 19:34:28 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.92) (envelope-from ) id 1jMyTs-0004Fo-Dw; Fri, 10 Apr 2020 19:34:20 +0100 Date: Fri, 10 Apr 2020 19:34:20 +0100 From: Russell King - ARM Linux admin To: Andrew Lunn Subject: Re: [PATCH] ARM: do not assemble iwmmxt.S with LLVM toolchain Message-ID: <20200410183420.GE25745@shell.armlinux.org.uk> References: <20200409232728.231527-1-caij2003@gmail.com> <20200410165948.GD448831@lunn.ch> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200410165948.GD448831@lunn.ch> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200410_113517_802375_B59EF1B9 X-CRM114-Status: GOOD ( 13.67 ) 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: Linus Walleij , Peter.Smith@arm.com, stefan@agner.ch, David Howells , Mauro Carvalho Chehab , manojgupta@google.com, Benjamin Gaignard , "Joel Fernandes \(Google\)" , Jian Cai , Bartosz Golaszewski , ilie.halip@gmail.com, Masahiro Yamada , Krzysztof Kozlowski , clang-built-linux@googlegroups.com, samitolvanen@google.com, Masami Hiramatsu , Arnd Bergmann , "Steven Rostedt \(VMware\)" , jiancai@google.com, Doug Anderson , Dan Williams , linux-arm-kernel@lists.infradead.org, Greg Kroah-Hartman , ndesaulniers@google.com, linux-kernel@vger.kernel.org, Patrick Bellasi , "Eric W. Biederman" , Tejun Heo , Andrew Morton 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 Fri, Apr 10, 2020 at 06:59:48PM +0200, Andrew Lunn wrote: > On Thu, Apr 09, 2020 at 04:27:26PM -0700, Jian Cai wrote: > > iwmmxt.S contains XScale instructions > > Dumb question.... > > Are these Xscale instructions? My understanding is that they are an > instruction set of their own, implementing something similar to IA-32 > MMX. > > Would it be more accurate to say CLANG does not support the iwmmxt > instruction set? Yes, because the XScale core on its own (otherwise known as 80200) doesn't support iWMMXT. It's worth pointing out that the iWMMXT instruction set uses the co-processor #1 instruction space as defined by the ARMv5 ARM ARM, which is also the FPA (floating point accelerator) instruction space - which is the FP instruction set prior to VFP. The LDFP and similar instructions that binutils decodes the opcodes as are FPA instructions, and the LDC2 instructions are their "generic co-processor" versions where there's no FPA instruction that matches the op-code. I'll also point out that the reason the iWMMXT code has never been ported to Thumb2 is because there are no equivalents for the co-processor instructions in the Thumb2 instruction set defined in ARMv5. Hence why the file has a .arm. So, the fact the file hasn't changed for a long time and hasn't been updated with "improvements" such as Thumb2 kernels is because that's completely irrelevent to the ISA. It is an example of code that has become stable and mature, and requires no maintanence with GNU toolchains. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 10.2Mbps down 587kbps up _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel