Re: [PATCH v6 05/11] rules.mak: Add base-arch() rule

["Alex Bennée" <alex.bennee@linaro.org>]

Philippe Mathieu-Daudé <philmd@redhat.com> writes:

> Add a rule to return the base architecture for a QEMU target.
>
> The current list of TARGET_BASE_ARCH is:
>
>   $ git grep  TARGET_BASE_ARCH configure
>   configure:7785:TARGET_BASE_ARCH=""
>   configure:7795:    TARGET_BASE_ARCH=i386
>   configure:7813:    TARGET_BASE_ARCH=arm
>   configure:7846:    TARGET_BASE_ARCH=mips
>   configure:7854:    TARGET_BASE_ARCH=mips
>   configure:7864:    TARGET_BASE_ARCH=openrisc
>   configure:7871:    TARGET_BASE_ARCH=ppc
>   configure:7879:    TARGET_BASE_ARCH=ppc
>   configure:7887:    TARGET_BASE_ARCH=ppc
>   configure:7894:    TARGET_BASE_ARCH=riscv
>   configure:7900:    TARGET_BASE_ARCH=riscv
>   configure:7920:    TARGET_BASE_ARCH=sparc
>   configure:7925:    TARGET_BASE_ARCH=sparc

This seems backwards. We encode the base architecture in configure.sh
because this is where we can make such distinctions. We then:

  echo "TARGET_BASE_ARCH=$TARGET_BASE_ARCH" >> $config_target_mak

Precisely so the make system can know what it is for any given target.
So:

> +# base-arch
> +# Usage: $(call base-arch, target)
> +#
> +# @target: the target architecture.
> +#
> +# This macro will return the base architecture for a target.
> +#
> +# As example, $(call base-arch, aarch64) returns 'arm'.
> +base-arch = $(strip \
> +		$(if $(call startwith,aarch64,$1),arm,\
> +		  $(if $(call startwith,arm,$1),arm,\
> +		    $(if $(call startwith,microblaze,$1),microblaze,\
> +		      $(if $(call startwith,mips,$1),mips,\
> +		        $(if $(call startwith,ppc,$1),ppc,\
> +		          $(if $(call startwith,riscv,$1),riscv,\
> +		            $(if $(call startwith,sh4,$1),sh4,\
> +		              $(if $(call startwith,sparc,$1),sparc,\
> +		                $(if $(call startwith,xtensa,$1),xtensa,\
> +		                  $(if $(call strequal,x86_64,$1),i386,\
> +		                    $1\
> +		                   )\
> +		                 )\
> +		               )\
> +		             )\
> +		           )\
> +		         )\
> +		       )\
> +		     )\
> +		   )\
> +		 )\
> +		)

Seems like a replication of information already calculated in configure
and prone to breakage if we add a new one (or come up with some franken
architecture at a later date).

-- 
Alex Bennée