cargo-show-asm

A cargo subcommand that displays the Assembly, LLVM-IR and MIR generated for Rust source code.

Install

cargo install cargo-show-asm

Features

Platform support:
- OS: Linux and MacOSX. Limited support for Windows
- Rust: nightly and stable.
- Architectures: x86, x86_64, aarch64, probably more but untested.
- Crosscompilation support.

Missing operating systems and architenctures might be supported by accident, please make a ticket if something not working for your favorite platform

Displaying:
- Assembly in Intel or AT&T syntax.
- Corresponding Rust source code alongside assembly.
- llvm-ir.
- rustc MIR

Usage:

You can start by running cargo asm with no parameters - it will suggests how to narrow the search scope - for workspace crates you need to specify a crate to work with, for crates defining several targets (lib, binaries, examples) you need to specify exactly which target to use. In a workspace cargo asm lists only workspace members as suggestions but any crate from workspace tree is available.

Once cargo asm focues on a single target it will run rustc producing assembly file and will try to list of available public functions:

% cargo asm --lib
Try one of those
"<&T as core::fmt::Display>::fmt" [17, 12, 12, 12, 12, 19, 19, 12]
"<&mut W as core::fmt::Write>::write_char" [20]
"<&mut W as core::fmt::Write>::write_fmt" [38]
"<&mut W as core::fmt::Write>::write_str" [90]
"<F as nom::internal::Parser<I,O,E>>::parse" [263]
...

Name in quotes is demangled rust name, numbers in square brackets represent number of lines in asm file. Function with the same name can be present in several instances.

Specifying exact function name will print its assembly code

% cargo asm --lib "cargo_show_asm::opts::focus::{{closure}}"

To pick between different alternatives you can either specify the index

% cargo asm --lib "cargo_show_asm::opts::focus::{{closure}}" 2

Or start using full names with hex included:

% cargo asm --lib --full-name
....
% cargo asm --lib "once_cell::imp::OnceCell<T>::initialize::h9c5c7d5bd745000b"

cargo-show-asm comes with a built in search function. Just pass partial name instead of a full one and only matching functions will be listed

% cargo asm --lib Debug

License

This project is licensed under either of

Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution