LLVM fatal error when compiling Rust language source code

[lexxvir]

Hi,

I compiling Rust source code using your LLVM fork and custom built Rust compiler used this fork. I can successfully compile simple functions that works! But when I tried to use alloc crate, I encountered to following error from LLVM:

EmitRawText called on an MCStreamer that doesn't support it,  something must not be fully mc'ized

Code that reproduce issue https://github.com/lexxvir/xtensa-rust-quickstart/blob/master/src/main.rs

Could you please give me any clue whats going on and how to fix it?
It seems that Rust compiler try to emit object code using LLVM, instead of emit assemble and then run gcc's assembler.

Thanks in advance, I will be glad to any help.

[andreisfr]

Hi @lexxvir ,

Yes, probably Rust compiler is trying to generate object files by some reason. The object files generation will be available in next releases of the LLVM Xtensa backend. Currently you could try to use some kind of wrapper program like as described here espressif/llvm-xtensa#1 (comment) to fix problem

[lexxvir]

Hi @andreisfr,

Thank you for response. As I understand, Rust compiler directly calls some LLVM's functions to produce code, see https://github.com/rust-lang/rust/blob/05b4554e77ef32a97060b1bfffd1f621bf15bb88/src/librustc_codegen_llvm/allocator.rs#L12.

If possible, could you please drop a comment in this issue when xtensa LLVM got object file generation support, so I'll can recheck behavior.

[andreisfr]

Hi @lexxvir ,

Ok, I will inform you when obect file generation will be ready

[ciniml]

I've also encountered the same problem, but I finally found that disabling the LTO causes this problem.

The LLVM backend tries to emit object code instead of assembly file even if no-integrated-as is specified in the rustc's Xtensa target information if ThinLTO pass is enabled.

To solve this, just enable full LTO in Cargo.toml of your Rust crate by setting lto=true

[gnzlbg]

How are you using this LLVM version with rustc ? Are you re-applying Rust LLVM patches to it? Rust is currently following a very recent LLVM trunk, but it appears that this fork is quite old.

[ciniml]

According to this instruction, a bit older version of rustc supports LLVM 6.0, which is the base version of llvm-xtensa.

I'm currently using rustc 1.34.0 built with llvm-xtensa

[lexxvir]

It seems this issue is not actual because this LLVM fork is able to generate binary code.