Re: [PATCH v2] ARM: Define wfi() macro for v6 processors

[Arnd Bergmann <arnd@arndb.de>]

On Tuesday 08 February 2011 17:32:29 Russell King - ARM Linux wrote:
> On Tue, Feb 08, 2011 at 04:17:58PM +0100, Arnd Bergmann wrote:
> > On Tuesday 08 February 2011, Dave Martin wrote:
> > > CFLAGS_cpu_specific_object.o        += -march=armv7-a
> > > 
> > > Whether it's safe to do it depends on whether code from that file
> > > could ever get run on other processors.  I'm not so sure of the answer
> > > to that..., but perhaps someone else has a better idea.
> > 
> > We already do this a lot from arch/arm/mm/Makefile, and those
> > files are typically just one function per file, so they can easily
> > be proven to be safe that way.
> 
> No, we do that with assembly files.  It doesn't work soo well with
> C files as we really don't want GCC itself to generate v7 instructions
> unless we explicitly ask for them.
>
> The other issue here is that somtimes generating code with different
> -march options leads to the linker refusing to link them together...

Ok, I see. Is that a bug in existing toolchains, or something more
fundamental?

I would have expected that you could at least mix all compiler options
that don't impact the ABI or the instruction set like -mthumb.

Also, I think we can still build with e.g. "-march=armv6 -Wa,-march=armv7",
which should tell the compiler to only emit armv6 instructions, but make
the assembler more permissive for inline assembly.

	Arnd