Compiler error when building on custom x86_64 no_std target

[Kevin Boos]

I ran into this error when trying to add the cstr_core crate to my no_std OS project, which depends on memchr and disables its default features.

Building in debug mode:

LLVM ERROR: Do not know how to split this operator's operand!

Building in release mode:

error: Could not compile `memchr`.

Caused by:
  process didn't exit successfully: `rustc --crate-name memchr /home/kevin/.cargo/registry/src/github.com-1ecc6299db9ec823/memchr-2.2.1/src/lib.rs --color always --crate-type lib --emit=dep-info,metadata,link -C opt-level=3 -C codegen-units=1 -C metadata=ebf07e953eacc227 -C extra-filename=-ebf07e953eacc227 --out-dir /home/kevin/my_os/target/x86_64-my_os/release/deps --target x86_64-my_os -L dependency=/home/kevin/my_os/target/x86_64-my_os/release/deps -L dependency=/home/kevin/my_os/target/release/deps --cap-lints allow --emit=obj -C debuginfo=2 -C code-model=large -C relocation-model=static -D unused-must-use -Z merge-functions=disabled -Z share-generics=no --sysroot /home/kevin/.xargo --cfg memchr_runtime_simd --cfg memchr_runtime_sse2 --cfg memchr_runtime_sse42 --cfg memchr_runtime_avx` (signal: 11, SIGSEGV: invalid memory reference)

For reference and in case it matters, my compiler target .json file is:

{
  "llvm-target": "x86_64-unknown-none-gnu",
  "data-layout": "e-m:e-i64:64-f80:128-n8:16:32:64-S128",
  "linker-flavor": "gcc",
  "target-endian": "little",
  "target-pointer-width": "64",
  "target-c-int-width": "32",
  "arch": "x86_64",
  "os": "none",
  "features": "-mmx,-sse,+soft-float",
  "disable-redzone": true,
  "panic": "abort"
}

My rustc version is rustc 1.38.0-nightly (78ca1bda3 2019-07-08).

I've never encountered an error like this before, so I'm not sure what else to say. If more information is needed, I am happy to provide it.

[Andrew Gallant]

Thanks for the bug report, but this doesn't appear actionable to me. Firstly, I don't know how to take the information you've given me and reproduce your error. (What commands should I run? What do I do with your JSON file?) Secondly, any LLVM error one sees is unlikely to be something that crate authors can do something about. I don't have any insight in to how to debug it.

"features": "-mmx,-sse,+soft-float"

This crate makes extensive use of SIMD CPU instructions on x86_64: https://github.com/BurntSushi/rust-memchr/blob/master/src/x86/sse2.rs --- So your problem may be around that.

[Kevin Boos]

I figured as much, but I decided to post the issue just in case you or others had seen this problem previously, or for anyone who may encounter it in the future. Appreciate your quick response!

The good news is that I tried a few different compiler versions, and it just seems to be a compatibility problem with my older nightly version. Using the latest nightly compiler worked for me, as did downgrading to memchr 2.1.3 on my nightly version from 2019-07-08.

Thanks again, and sorry to bother!

[Andrew Gallant]

Oh interesting, that's good to know! Glad to hear it's working.