Cross compiling for ARC processor (Argonaut RISC Core)

help
1

I've followed the adding a new target rustc-dev guide using a pre-built LLVM. Note that ARC is an experimental LLVM target (like m68k). I'm attempting to compile for the arc-unknown-none-elf target triple. What I've done so far:

  • Specify pre-built llvm-config path in config.toml.
  • Created a target specification JSON file.
  • Modified supported_targets macro in rustc_target::spec and created a target rs file.
  • If I run llvm-config --targets-built with the pre-built llvm-config I get X86 ARC so LLVM should support it.
  • Added elf to target_os and arc to target_arch in EXTRA_CHECK_CFGS as described by rustc-dev
  • Ran DESTDIR=/path/to/destdir ./x install -i --stage 1 --host arc-unknown-none-elf.json --target arc-unknown-non-elf compiler/rustc

After running ./x install above I get to the step:
Creating a sysroot for stage1 compiler (use rustup toolchain link 'name' build/host/stage1)
Building stage0 library artifacts (x86_64-unknown-linux-gnu -> arc-unknown-none-elf(arc-unknown-none-elf.json))

It fails due to the error: error: could not create LLVM TargetMachine for triple: arc-unknown-none-elf: No available targets are compatible with triple "arc-unknown-none-elf".

2

If you don't get an answer here, you may want to ask on the internals forum as well.

There's a bit of overlap, but most of the people on the user forums are end users of Rust, whereas most of the people on the internal forums are working on the language itself. There's also a Zulip server that a lot of the compiler people hang out on.

1 Like
3

You can also try the rust-dev channel in discord.

4

You need to add something like https://github.com/rust-lang/rust/blob/1e836d12d39ea09b1d86ebda70cb11b41564cead/compiler/rustc_llvm/src/lib.rs#L57 for the new target.

5

Thanks for the help.
I added the init_target! macro call and added arc to OPTIONAL_COMPONENTS in rustc_llvm/build.rs.
However after running ./x install I saw that ARC doesn't implement LLVMInitializeARCAsmParser like other ISA's (e.g. LLVMInitializeRISCVAsmParser) After removing the AsmParser from the macro, I got the same error I initially described. Is something like LLVMInitializeARCAsmParser necessary for Rust? Or is it only needed for inline assembly?

6

LLVM may be missing an integrated assembler for ARC. Rustc doesn't support invoking an external assembler.

7

it does according to LLVM: lib/Target/M68k Directory Reference and LLVM: lib/Target/ARC Directory Reference

8

Where in M68k's directory reference and ARC's directory reference do you see you can invoke an external assembler?

9

Hey @rusty0, I wanted to follow up and ask if you had any idea on how to use an external assembler for rustc and where in the LLVM directory reference's it's discussed.

10

I got Rust code to compile for the arc-elf32 target using rustc_codegen_gcc and using Heath123's rust-casio-docker repository. Modifications to rust-casio-docker:

You can test the compiled Rust code using QEMU. Follow kolerov's synopsys repository on how to build QEMU for ARC.

Note that ./test.sh in rustc_codegen_gcc still fails.

  • The first issue you'll experience is an arc_legitimize_tls_address issue.
  • So remove the thread-local storage (TLS) related tests in example/mini_core.rs.
  • The second issue is that arc-elf32-ld can't find libc. I haven't figured out a solution to that yet.