`cargo-show-asm` can misidentify functions in the assembly

[SludgePhD]

I have a generic function instantiated with f32 and a Vec1f vector type. Running cargo asm and listing the instantiation for Vec1f shows the same output as the instance for f32, while in reality (and confirmed with --disasm and objdump -S) they contain wildly different code.

I haven't managed to reduce this yet, but the symbols in question look like this (after demangling):

• benches::bench_zip::<zaru_linalg::vector::Vector<f32, zaru_linalg::dim::Const<1>>>::{closure#0}
• benches::bench_zip::<f32>::{closure#0}

I am using the v0 symbol mangling instead of the legacy one, maybe the assembly parser doesn't like that?

[pacak]

I'm using rustc_demangle [1], whatever it supports works.

Nothing specific comes to mind. Try passing -vvv and see what file it tries to work with and check if symbols are indeed pointing to identical code.

1. https://docs.rs/rustc-demangle/latest/rustc_demangle/

[SludgePhD]

Ah, I think it's happening because cargo asm passes -Ccodegen-units=1 to rustc, but only when --disasm is absent.

So the generated code for f32 and the vector type is indeed identical, but only when building with a single codegen unit.

[pacak]

Same as more tickets - blocked on cargo: rust-lang/cargo#13672