[Mesa-dev] [PATCH] meson: Clarify why asm cannot be used in cross compile

[Eric Engestrom]

On Thursday, 2018-06-07 10:11:39 -0700, Dylan Baker wrote:
> This makes the reasoning for why a cross compile is not using asm
> clearer (hopefully).
> 
> Signed-off-by: Dylan Baker <dylan.c.baker at intel.com>
> ---
>  meson.build | 24 +++++++++++++++++-------
>  1 file changed, 17 insertions(+), 7 deletions(-)
> 
> diff --git a/meson.build b/meson.build
> index 4d4ca5d5578..4e96a074698 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -841,14 +841,24 @@ endif
>  # TODO: powr8
>  # TODO: shared/static? Is this even worth doing?
>  
> -# Building x86 assembly code requires running x86 binaries. It is possible for
> -# x86_64 OSes to run x86 binaries, so don't disable asm in those cases
> -# TODO: it should be possible to use an exe_wrapper to run the binary during
> -# the build. 
> +# When cross compiling we generally need to turn off the use of assmebly,

"assembly"

> +# because mesa's assmebly relies on building an exectuable for the host system,

"assembly", "executable"

With those:
Reviewed-by: Eric Engestrom <eric.engestrom at intel.com>

> +# and running it to get information about struct sizes. There is at least one
> +# case of cross compiling where we can use asm, and that's x86_64 -> x86 when
> +# host OS == build OS, since in that case the build machine can run the host's
> +# binaries.
>  if meson.is_cross_build() 
> -  if not (build_machine.cpu_family() == 'x86_64' and host_machine.cpu_family() == 'x86'
> -          and build_machine.system() == host_machine.system())
> -    message('Cross compiling to x86 from non-x86, disabling asm')
> +  if build_machine.system() != host_machine.system()
> +    # TODO: It may be possible to do this with an exe_wrapper (like wine).
> +    message('Cross compiling from one OS to another, disabling assembly.')
> +    with_asm = false
> +  elif not (build_machine.cpu_family() == 'x86_64' and host_machine.cpu_family() == 'x86')
> +    # TODO: There may be other cases where the 64 bit version of the
> +    # architecture can run 32 bit binaries (aarch64 and armv7 for example)
> +    message('''
> +      Cross compiling to different architectures, and the host cannot run
> +      the build machine's binaries. Disabling assembly.
> +    ''')
>      with_asm = false
>    endif
>  endif
> -- 
> 2.17.1
> 
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