[3.x] Add support for the RISC-V architecture

[aaronfranke]

Implements godotengine/godot-proposals#3374 on 3.x. Only Clang Debug builds work on RISC-V right now.

[akien-mga]

I would move this to the Linux detect.py too. It won't add the arch to extra_suffix, but this isn't done for i386, i686, x86_64, armv7hl or aarch64 on Linux currently, so we shouldn't do it for rv64 only.

Like it's done for aarch64 currently, it should be clear to someone compiling on RISC-V hardware that their godot.linuxbsd.opt.tools.64 binary targets RISC-V (especially if they passed arch=rv64 for that).

[akien-mga]

BTW, this check also makes it impossible to cross-compile from RISC-V to other architectures.

[aaronfranke]

I made the change locally to test it. To my surprise, it actually does add the arch to the suffix. It calls the configure method on line 397. So yeah, moving this to detect.py works well.

BTW, this check also makes it impossible to cross-compile from RISC-V to other architectures.

It's not possible to cross-compile for x86 regardless as far as I can tell. For this code specifically, it doesn't make it impossible because this code only runs if env["arch"] == "" so you just have to say arch=arm64 or arch=x86_64, even if it's not picked up by the engine, this will stop it from being equal to "". Still, as I mentioned it's not possible to cross-compile for x86 regardless, we don't have any code in the build system to tell the compiler to target x86. Also, cross-compiling from RISC-V is super niche :P

[akien-mga]

True, specifying a different arch would work. You can still cross-compile by passing CC and CXX manually to use the compilers for that architecture.

[akien-mga]

With the current form I think it's fine to merge for 3.4 even if it's not critical for that release. It's an extra option provided as is, without expectation that it actually works. But that's a start.

[akien-mga]

Thanks!

[danboid]

I'm going to try building godot under Debian sid on my VisionFive2. Am I right in thinking the build command is:

scons platform=linuxbsd use_llvm=yes

Thanks

[aaronfranke]

@danboid Yes, that is correct. Actually just scons use_llvm=yes should be sufficient and it will auto-detect platform=linuxbsd arch=rv64 from your OS and hardware.