Re: [PATCH] ARM: do not assemble iwmmxt.S with LLVM toolchain
From: Arnd Bergmann
Date: Fri Apr 10 2020 - 05:56:37 EST
On Fri, Apr 10, 2020 at 1:28 AM Jian Cai <caij2003@xxxxxxxxx> 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@xxxxxxxxx>
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?
- Why does the linker have to understand it, rather than just the assembler?
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 66a04f6f4775..39de8fc64a73 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -804,7 +804,7 @@ source "arch/arm/mm/Kconfig"
>
> config IWMMXT
> bool "Enable iWMMXt support"
> - depends on CPU_XSCALE || CPU_XSC3 || CPU_MOHAWK || CPU_PJ4 || CPU_PJ4B
> + depends on !AS_IS_CLANG && !LD_IS_LLD && (CPU_XSCALE || CPU_XSC3 || CPU_MOHAWK || CPU_PJ4 || CPU_PJ4B)
I would suggest splitting it into two lines for readability:
depends on CPU_XSCALE || CPU_XSC3 || CPU_MOHAWK || CPU_PJ4 || CPU_PJ4B
depends on !AS_IS_CLANG && !LD_IS_LLD
Arnd
[1] http://web.archive.org/web/20191015165247/https://www.marvell.com/embedded-processors/armada/index.jsp