`-Cpasses=loweratomic` is unknown on versions => 1.82

[nhtyy]

I search the 1.82 change logs and saw the llvm version was bumped, but no specific mention of this.

CARGO_ENCODED_RUSTFLAGS="-Cpasses=loweratomic" cargo run

fn main() {
   // hello world
}

I expected to see this happen:

The program to compile

Instead, this happened:

error: failed to run LLVM passes: unknown pass name 'loweratomic'

Tested on

1.79, 1.8, 1.81, 1.82, 1.83 by switching using rustup default ..

[bjorn3]

llvm/llvm-project#74287 renamed it to lower-atomic. In any case be aware that -Cpasses and -Cllvm-args don't have any stability guarantees. They are directly passed to LLVM which does change these things every once in a while. Also rustc can be compiled against older LLVM versions (like distros often do) in which case you have to use the corresponding version of the flag.

[nhtyy]

Thank you!