Fix assembly for x32 ABI

[abatyiev]

The x32 ABI is special ABI for long mode on x64, that uses 32 bit integers and pointers instead of 64 bit. This patch fixes assembly code for x32 ABI.

See https://bugs.gentoo.org/942562
https://wiki.debian.org/X32Port

[sneves]

I'll be honest, I thought x32 had been deprecated years ago. Is this something popular enough to warrant support?

[abatyiev]

Gentoo does support it and I'm using it.
The problem for me is that mesa uses BLAKE3 now and therefore I need a fix here.

[oconnor663]

What would be our options for CI testing this? Apart from what GH Actions provides directly, we use QEMU via cross-rs to test esoteric architectures (big endian etc.), but it doesn't look like cross-rs supports x32.

[abatyiev]

It seems like you are using Ubuntu: it has x32 support in regular x86_64 releases. (There are packages like gcc-13-x86-64-linux-gnux32, libc6-x32, binutils-x86-64-linux-gnux32 etc). One way to provide correct compiler for the build system is to use CMake's toolchain file ( https://cmake.org/cmake/help/latest/manual/cmake-toolchains.7.html

Basically you need a regular amd64 kernel with CONFIG_X86_X32=y and a toolchain. Regular amd64 ABI and x32 ABI can coexist (together with i686 ABI) on the same machine.