Re: [PATCH] ARM: do not assemble iwmmxt.S with LLVM toolchain

From: Andrew Lunn <andrew@lunn.ch>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Linus Walleij <linus.walleij@linaro.org>,
	Peter Smith <Peter.Smith@arm.com>, Stefan Agner <stefan@agner.ch>,
	David Howells <dhowells@redhat.com>,
	Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
	Manoj Gupta <manojgupta@google.com>,
	Benjamin Gaignard <benjamin.gaignard@linaro.org>,
	"Joel Fernandes (Google)" <joel@joelfernandes.org>,
	Jian Cai <caij2003@gmail.com>,
	clang-built-linux <clang-built-linux@googlegroups.com>,
	Ilie Halip <ilie.halip@gmail.com>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Russell King <linux@armlinux.org.uk>,
	Krzysztof Kozlowski <krzk@kernel.org>,
	Bartosz Golaszewski <bgolaszewski@baylibre.com>,
	Sami Tolvanen <samitolvanen@google.com>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	"Steven Rostedt (VMware)" <rostedt@goodmis.org>,
	Jian Cai <jiancai@google.com>,
	Doug Anderson <armlinux@m.disordat.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Patrick Bellasi <patrick.bellasi@arm.com>,
	Masami Hiramatsu <mhiramat@kernel.org>, Tejun Heo <tj@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] ARM: do not assemble iwmmxt.S with LLVM toolchain
Date: Mon, 13 Apr 2020 23:15:08 +0200	[thread overview]
Message-ID: <20200413211508.GE436020@lunn.ch> (raw)
In-Reply-To: <CAKwvOdnpW0VSRdD6958xyWh-tDbuVTti265aqOpvfhvh6iQEXQ@mail.gmail.com>

On Mon, Apr 13, 2020 at 12:20:57PM -0700, Nick Desaulniers wrote:
> On Fri, Apr 10, 2020 at 2:56 AM Arnd Bergmann <arnd@arndb.de> wrote:
> >
> > On Fri, Apr 10, 2020 at 1:28 AM Jian Cai <caij2003@gmail.com> wrote:
> > >
> > > iwmmxt.S contains XScale instructions LLVM ARM backend does not support.
> > > Skip this file if LLVM integrated assemmbler or LLD is used to build ARM
> > > kernel.
> > >
> > > Signed-off-by: Jian Cai <caij2003@gmail.com>
> >
> > It clearly makes sense to limit the Kconfig option to compilers that
> > can actually build it.
> > A few questions though:
> >
> > - Given that Armada XP with its PJ4B was still marketed until fairly
> > recently[1],
> >   wouldn't it make sense to still add support for it? Is it a lot of work?
> 
> Sorry, can you help me verify from that link that PJ4B uses XSCALE?

I think you missed my email. iwmmxt is not Xscale. iwmmxt is an
instruction set of its own, which any ARM processor could implement.

> I
> didn't see references to either in the link provided.  Also, given the
> history of XSCALE as noted by Russell, I'm surprised to see Marvell in
> the mix.

https://en.wikipedia.org/wiki/XScale

	XScale comprises several distinct families: IXP, IXC, IOP, PXA
	and CE.

	Intel sold the PXA family to Marvell Technology Group
	in June 2006.[1] Marvell then extended the brand to include
	processors with other microarchitectures, like ARM's Cortex.

	Andrew