cargo-llvm-lines
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
Installation
Install with cargo install cargo-llvm-lines
.
Output
One line per function with three columns of output:
- Total number of lines of LLVM IR generated across all instantiations of the function (plus the percentage of the total and the cumulative percentage of all functions so far).
- Number of instantiations of the function (plus the percentage of the total and the cumulative percentage of all functions so far). For a generic function, the number of instantiations is 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
----- ------ -------------
52262 1872 (TOTAL)
1815 (3.5%, 3.5%) 1 (0.1%, 0.1%) <cargo_llvm_lines::Opt as clap::derive::Subcommand>::augment_subcommands
1806 (3.5%, 6.9%) 1 (0.1%, 0.1%) <cargo_llvm_lines::Opt as clap::derive::FromArgMatches>::from_arg_matches_mut
1546 (3.0%, 9.9%) 34 (1.8%, 1.9%) core::option::Option<T>::map
1045 (2.0%, 11.9%) 5 (0.3%, 2.2%) clap::parser::matches::arg_matches::ArgMatches::try_remove_arg_t
738 (1.4%, 13.3%) 2 (0.1%, 2.3%) alloc::slice::merge_sort
648 (1.2%, 14.5%) 4 (0.2%, 2.5%) alloc::raw_vec::RawVec<T,A>::grow_amortized
645 (1.2%, 15.8%) 6 (0.3%, 2.8%) <alloc::vec::Vec<T> as alloc::vec::spec_from_iter_nested::SpecFromIterNested<T,I>>::from_iter
636 (1.2%, 17.0%) 43 (2.3%, 5.1%) <cargo_llvm_lines::Opt as clap::derive::FromArgMatches>::from_arg_matches_mut::{{closure}}
587 (1.1%, 18.1%) 15 (0.8%, 5.9%) <core::result::Result<T,E> as core::ops::try_trait::Try>::branch
565 (1.1%, 19.2%) 6 (0.3%, 6.2%) core::iter::traits::iterator::Iterator::try_fold
533 (1.0%, 20.2%) 1 (0.1%, 6.3%) cargo_llvm_lines::print_table
520 (1.0%, 21.2%) 6 (0.3%, 6.6%) alloc::vec::Vec<T,A>::extend_desugared
509 (1.0%, 22.2%) 5 (0.3%, 6.9%) clap::parser::matches::any_value::AnyValue::downcast_into
504 (1.0%, 23.1%) 5 (0.3%, 7.2%) alloc::sync::Arc<T>::try_unwrap
470 (0.9%, 24.0%) 11 (0.6%, 7.7%) core::option::Option<T>::ok_or_else
438 (0.8%, 24.9%) 2 (0.1%, 7.9%) alloc::slice::merge
414 (0.8%, 25.7%) 9 (0.5%, 8.3%) core::result::Result<T,E>::and_then
Multicrate Projects
Interpreting the output in the presence of multiple crates and generics can be
tricky. 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 -p
flag:
$ 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.