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Date: Mon, 13 Apr 2020 12:23:38 -0700 From: Nick Desaulniers <ndesaulniers@...gle.com> To: Russell King - ARM Linux admin <linux@...linux.org.uk> Cc: Ard Biesheuvel <ardb@...nel.org>, Arnd Bergmann <arnd@...db.de>, Jian Cai <caij2003@...il.com>, Linus Walleij <linus.walleij@...aro.org>, Peter Smith <Peter.Smith@....com>, Stefan Agner <stefan@...er.ch>, David Howells <dhowells@...hat.com>, Mauro Carvalho Chehab <mchehab+samsung@...nel.org>, Manoj Gupta <manojgupta@...gle.com>, Benjamin Gaignard <benjamin.gaignard@...aro.org>, "Joel Fernandes (Google)" <joel@...lfernandes.org>, clang-built-linux <clang-built-linux@...glegroups.com>, Ilie Halip <ilie.halip@...il.com>, Masahiro Yamada <masahiroy@...nel.org>, Krzysztof Kozlowski <krzk@...nel.org>, Bartosz Golaszewski <bgolaszewski@...libre.com>, Sami Tolvanen <samitolvanen@...gle.com>, "Eric W. Biederman" <ebiederm@...ssion.com>, "Steven Rostedt (VMware)" <rostedt@...dmis.org>, Jian Cai <jiancai@...gle.com>, Doug Anderson <armlinux@...isordat.com>, Dan Williams <dan.j.williams@...el.com>, Linux ARM <linux-arm-kernel@...ts.infradead.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Patrick Bellasi <patrick.bellasi@....com>, Masami Hiramatsu <mhiramat@...nel.org>, Tejun Heo <tj@...nel.org>, Andrew Morton <akpm@...ux-foundation.org> Subject: Re: [PATCH] ARM: do not assemble iwmmxt.S with LLVM toolchain On Fri, Apr 10, 2020 at 5:33 AM Russell King - ARM Linux admin <linux@...linux.org.uk> wrote: > > For older CPUs, it doesn't matter what the latest ARM ARM says, the > appropriate version of the ARM ARM is the one relevant for the CPU > architecture. This is a mistake frequently made, and it's been pointed > out by Arm Ltd in the past (before ARMv6 even came on the scene) that > keeping older revisions is necessary if you want to be interested in > the older architectures. As if it never existed *waves hands*. Interesting. Does ARM still distribute these older reference manuals? Do you keep copies of the older revisions? > > However, there's an additional complication here: DEC's license from > Arm Ltd back in the days of StrongARM allowed them to make changes to > the architecture - that was passed over to Intel when they bought that > part of DEC. Consequently, these "non-Arm vendor" cores contain > extensions that are not part of the ARM ARM. iWMMXT is one such > example, which first appeared in the Intel PXA270 SoC (an ARMv5 > derived CPU). > > In fact, several of the features found in later versions of the ARM > architecture came from DEC and Intel enhancements. > > If your compiler/assembler only implements what is in the latest ARM > ARM, then it is not going to be suitable for these older CPUs and > alternate vendor "ARM compatible" CPUs. This is a neat piece of history, thanks for sharing. -- Thanks, ~Nick Desaulniers
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