Count the number of lines of LLVM IR across all instantiations of a generic function. Based on a suggestion from @eddyb on how to count monomorphized functions in order to debug compiler memory usage, executable size and compile time.
<eddyb> unoptimized LLVM IR
<eddyb> first used grep '^define' to get only the lines defining function bodies
<eddyb> then regex replace in my editor to remove everything before @ and everything after (
<eddyb> then sort | uniq -c
cargo install cargo-llvm-lines.
One line per function with three columns of output:
- Total number of lines of LLVM IR generated across all instantiations of the function (and the percentage of the total).
- Number of instantiations of the function (and the percentage of the total). For a generic function, roughly the number of distinct combinations of generic type parameters it is called with.
- Name of the function.
$ cargo llvm-lines | head -20 Lines Copies Function name ----- ------ ------------- 30737 (100%) 1107 (100%) (TOTAL) 1395 (4.5%) 83 (7.5%) core::ptr::drop_in_place 760 (2.5%) 2 (0.2%) alloc::slice::merge_sort 734 (2.4%) 2 (0.2%) alloc::raw_vec::RawVec<T,A>::reserve_internal 666 (2.2%) 1 (0.1%) cargo_llvm_lines::count_lines 490 (1.6%) 1 (0.1%) <std::process::Command as cargo_llvm_lines::PipeTo>::pipe_to 476 (1.5%) 6 (0.5%) core::result::Result<T,E>::map 440 (1.4%) 1 (0.1%) cargo_llvm_lines::read_llvm_ir 422 (1.4%) 2 (0.2%) alloc::slice::merge 399 (1.3%) 4 (0.4%) alloc::vec::Vec<T>::extend_desugared 388 (1.3%) 2 (0.2%) alloc::slice::insert_head 366 (1.2%) 5 (0.5%) core::option::Option<T>::map 304 (1.0%) 6 (0.5%) alloc::alloc::box_free 296 (1.0%) 4 (0.4%) core::result::Result<T,E>::map_err 295 (1.0%) 1 (0.1%) cargo_llvm_lines::wrap_args 291 (0.9%) 1 (0.1%) core::char::methods::<impl char>::encode_utf8 286 (0.9%) 1 (0.1%) cargo_llvm_lines::run_cargo_rustc 284 (0.9%) 4 (0.4%) core::option::Option<T>::ok_or_else
Interpreting the output in the presence of multiple crates and generics can be
cargo llvm-lines only shows the contribution of the root crate;
dependencies are not included. To assess the contribution of an intermediate
crate, use the
$ cargo llvm-lines -p some-depenency
Note however, that Rust generics are monomorphised — a generic function will be accounted for in the crates that use it, rather than in the defining crate.
There is a trick to get a holistic view: enabling link time optimization causes all code generation to happen in the root crate. So you can use the following invocation to get a full picture:
$ CARGO_PROFILE_RELEASE_LTO=fat cargo llvm-lines --release
Licensed under either of LicenseApache License, Version 2.0 or MIT license at your option.
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this crate by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.