Re: [PATCH] arm: Support -mfdpic for more targets

["Richard Earnshaw (lists)" <Richard.Earnshaw@arm.com>]

On 24/02/2024 03:33, Fangrui Song wrote:
> From: Fangrui Song <maskray@gcc.gnu.org>
> 
> Targets that are not arm*-*-uclinuxfdpiceabi can use -S -mfdpic, but -c
> -mfdpic does not pass --fdpic to gas.  This is an unnecessary
> restriction.  Just define the ASM_SPEC in bpabi.h.
> 
> Additionally, use armelf[b]_linux_fdpiceabi emulations for -mfdpic in
> linux-eabi.h.  This will allow a future musl fdpic port to use the
> desired BFD emulation.
> 
> gcc/ChangeLog:
> 
> 	* config/arm/bpabi.h (TARGET_FDPIC_ASM_SPEC): Transform -mfdpic.
> 	* config/arm/linux-eabi.h (TARGET_FDPIC_LINKER_EMULATION): Define.
> 	(SUBTARGET_EXTRA_LINK_SPEC): Use TARGET_FDPIC_LINKER_EMULATION
> 	if -mfdpic.

Firstly, my apologies for the delay replying on this patch.

I'm not sure why we'd want a linux target to use fdpic, but this is pretty harmless, so OK.

R.

> ---
>  gcc/config/arm/bpabi.h      | 2 +-
>  gcc/config/arm/linux-eabi.h | 5 ++++-
>  2 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/gcc/config/arm/bpabi.h b/gcc/config/arm/bpabi.h
> index 7a279f3ed3c..6778be1a8bf 100644
> --- a/gcc/config/arm/bpabi.h
> +++ b/gcc/config/arm/bpabi.h
> @@ -55,7 +55,7 @@
>  #define TARGET_FIX_V4BX_SPEC " %{mcpu=arm8|mcpu=arm810|mcpu=strongarm*"\
>    "|march=armv4|mcpu=fa526|mcpu=fa626:--fix-v4bx}"
>  
> -#define TARGET_FDPIC_ASM_SPEC ""
> +#define TARGET_FDPIC_ASM_SPEC "%{mfdpic: --fdpic}"
>  
>  #define BE8_LINK_SPEC							\
>    "%{!r:%{!mbe32:%:be8_linkopt(%{mlittle-endian:little}"		\
> diff --git a/gcc/config/arm/linux-eabi.h b/gcc/config/arm/linux-eabi.h
> index eef791f6a02..0c5c58e4928 100644
> --- a/gcc/config/arm/linux-eabi.h
> +++ b/gcc/config/arm/linux-eabi.h
> @@ -46,12 +46,15 @@
>  #undef  TARGET_LINKER_EMULATION
>  #if TARGET_BIG_ENDIAN_DEFAULT
>  #define TARGET_LINKER_EMULATION "armelfb_linux_eabi"
> +#define TARGET_FDPIC_LINKER_EMULATION "armelfb_linux_fdpiceabi"
>  #else
>  #define TARGET_LINKER_EMULATION "armelf_linux_eabi"
> +#define TARGET_FDPIC_LINKER_EMULATION "armelf_linux_fdpiceabi"
>  #endif
>  
>  #undef  SUBTARGET_EXTRA_LINK_SPEC
> -#define SUBTARGET_EXTRA_LINK_SPEC " -m " TARGET_LINKER_EMULATION
> +#define SUBTARGET_EXTRA_LINK_SPEC " -m %{mfdpic: " \
> +  TARGET_FDPIC_LINKER_EMULATION ";:" TARGET_LINKER_EMULATION "}"
>  
>  /* GNU/Linux on ARM currently supports three dynamic linkers:
>     - ld-linux.so.2 - for the legacy ABI