[Mesa-dev] [PATCH] meson: Allow use of ASM for x86 host with x86_64 build machine

[Eric Engestrom]

On Thursday, 2018-06-07 09:19:29 -0700, Dylan Baker wrote:
> The reason we restrict the use of ASM when cross compiling is that there
> is a C based generator (mtypes) that must be run as part of the build
> process, and it must be built for the host architecture. In the case of
> an x86 host and an x86_64 build machine this is possible as long as the
> host and build OSes are the same (ie, not Windows -> Linux).

This would be great as a comment at the start of that block in meson.build ;)

> 
> This also makes the commit message a bit more generic than it previously
> was.
> 
> CC: Mike Lothian <mike at fireburn.co.uk>
> Fixes: 2d62fc06465281d3d45b8a7c7fd2b17ef718448c
>        ("meson: disable x86 asm in fewer cases.")
> Signed-off-by: Dylan Baker <dylan.c.baker at intel.com>
> ---
> 
> I've convinced myself this is correct, but it's a lot of logic to hold in my
> head at 9am...
> 
>  meson.build | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/meson.build b/meson.build
> index 4d4ca5d5578..31557d095dc 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -846,9 +846,15 @@ endif
>  # TODO: it should be possible to use an exe_wrapper to run the binary during
>  # the build. 
>  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() or
> +      not (build_machine.cpu_family() == 'x86_64' and host_machine.cpu_family() == 'x86'))

I'm 99% sure you're not changing the logic here :)

If you drop the above, everything below is:
Reviewed-by: Eric Engestrom <eric.engestrom at intel.com>

(with an appropriate commit message)

> +    # 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 with non-binary compatible host and build systems.
> +      Either with a non-binary compatible architecture pair, or with different
> +      host and build OSes.'''
> +    )
>      with_asm = false
>    endif
>  endif
> -- 
> 2.17.1
> 
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