multitarget-issue VS cargo-asm

I have created a minimal reproducible example at https://github.com/mrtims/multitarget-issue

cargo asm might be useful here (if you can't use godbolt).

They should be inlined in release mode. You'd have to verify by checking the assembly, though, which could be done directly in the Rust playground or with a tool like cargo-asm.

You can use cargo asm - not sure if you can integrate it with VSCode, but even from a terminal it's a pretty convenient tool.

There's probably a built-in one somewhere, but I suspect it'd be easier just to install https://github.com/gnzlbg/cargo-asm

I don't know if there's a way to do a side by side comparison but cargo-asm uses the source mapping information from rustc to annotate chunks of assembly with it's respective rust code, though it's an imperfect process.

After that you would need some tools to help figure out how to achieve improvements. That will depend on your system and personal preferences. As the other commenter suggested, perf is a good choice on linux. I personally like to look at the generated assembly, using either cargo asm, godbolt, or just rust playground.

Doesn't this already exist? https://github.com/gnzlbg/cargo-asm

From the flamegraph, we knew which function was taking the majority of the time, which we briefly described above. We started by looking at the assembly code it generated to see if there were any opportunities to make it faster. We did this with cargo-asm.

You're best bet at the moment is probably using cargo-asm to inspect the function assembly to see when it is performing the correct TCO.