Crates.io | cargo-llvm-lines |
lib.rs | cargo-llvm-lines |
version | 0.4.39 |
source | src |
created_at | 2017-11-30 08:31:14.03465 |
updated_at | 2024-05-17 02:16:10.37988 |
description | Count the number of lines of LLVM IR across all instantiations of a generic function. |
homepage | |
repository | https://github.com/dtolnay/cargo-llvm-lines |
max_upload_size | |
id | 41089 |
size | 55,228 |
This tool measures the number and size of instantiations of each generic function in a program, indicating which parts of your code offer the highest leverage in improving compilation metrics.
Generic functions in Rust can be instantiated multiple times, so they can disproportionately affect compile time, compiler memory usage, and the size of compiled executables.
Install with cargo install cargo-llvm-lines
.
Example output from running cargo llvm-lines
on its own codebase:
$ cargo llvm-lines | head -20
Lines Copies Function name
----- ------ -------------
51637 1222 (TOTAL)
2240 (4.3%, 4.3%) 1 (0.1%, 0.1%) <cargo_llvm_lines::opts::LlvmLines as clap_builder::derive::Args>::augment_args
1190 (2.3%, 6.6%) 1 (0.1%, 0.2%) <cargo_llvm_lines::opts::LlvmLines as clap_builder::derive::FromArgMatches>::from_arg_matches_mut
1005 (1.9%, 8.6%) 3 (0.2%, 0.4%) alloc::raw_vec::RawVec<T,A>::grow_amortized
973 (1.9%, 10.5%) 7 (0.6%, 1.0%) clap_builder::parser::matches::arg_matches::ArgMatches::try_remove_arg_t
939 (1.8%, 12.3%) 7 (0.6%, 1.6%) alloc::sync::Arc<T>::try_unwrap
935 (1.8%, 14.1%) 6 (0.5%, 2.0%) <alloc::vec::Vec<T> as alloc::vec::spec_from_iter_nested::SpecFromIterNested<T,I>>::from_iter
861 (1.7%, 15.8%) 7 (0.6%, 2.6%) alloc::sync::Arc<dyn core::any::Any+core::marker::Send+core::marker::Sync>::downcast
761 (1.5%, 17.2%) 5 (0.4%, 3.0%) alloc::vec::Vec<T,A>::extend_desugared
638 (1.2%, 18.5%) 1 (0.1%, 3.1%) cargo_llvm_lines::table::print
599 (1.2%, 19.6%) 16 (1.3%, 4.4%) core::option::Option<T>::ok_or_else
592 (1.1%, 20.8%) 2 (0.2%, 4.6%) core::slice::sort::merge
574 (1.1%, 21.9%) 2 (0.2%, 4.7%) core::slice::sort::merge_sort
561 (1.1%, 23.0%) 7 (0.6%, 5.3%) clap_builder::parser::matches::any_value::AnyValue::downcast_into
556 (1.1%, 24.1%) 4 (0.3%, 5.6%) <core::slice::iter::Iter<T> as core::iter::traits::iterator::Iterator>::next
541 (1.0%, 25.1%) 16 (1.3%, 7.0%) core::option::Option<T>::map
536 (1.0%, 26.1%) 8 (0.7%, 7.6%) <alloc::sync::Weak<T> as core::ops::drop::Drop>::drop
533 (1.0%, 27.2%) 1 (0.1%, 7.7%) core::str::pattern::simd_contains
There is one line per function with three columns of output:
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-dependency
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
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