[Patch] libffi: Add MIPS64 support.

[Richard Sandiford]

David Daney <ddaney@avtrex.com> writes:
> This patch adds full MIPS64 support to libffi.  Previously libffi had 
> disabled MIPS64 and the code that was there failed many test cases.

Thanks for doing this.

> In addition to cleaning up the existing code and fixing some failing 
> corner cases, I added support for ffi closures and throwing of 
> exceptions through libffi.  Most of the changes only touch the n32 and 
> n64 ABIs which had previously been disabled.  The one exception was to 
> move a parameter to a different register($12) in the o32 closure code so 
> that the trampoline generation code could be shared with n32.
>
> Tested on x86_64-pc-linux-gnu, mips64-linux{o32, n32, n64} with no 
> failures in the libffi testsuite.
>
> OK to Commit?

Looks good to me.  I can't claim to have mulled over every line,
but I couldn't see anything obvious reading through.  One question
though:

> +          /* The size of a pointer depends on the ABI */
> +          if (type == FFI_TYPE_POINTER)
> +            type =
> +              (ecif->cif->abi == FFI_N64) ? FFI_TYPE_UINT64 : FFI_TYPE_UINT32;

Was there a reason for preferring UINT to SINT here?  Naively, I'd have
expected to see pointers treated as signed, especially for n32.  I can well
imagine it makes no practical difference.  I just thought I'd ask.

Also, as a minor nit, the patch mixed space and tab indentation quite a bit,
which made it hard to read (and might make future patches hard to read).
I won't insist that you change it though.

OK if no-one more familiar with the code objects in 24 hours.

Richard