`cargo clippy` is sometimes >20x slower than `cargo check` (since `1.58.0`)

[wtfsck]

Summary

cargo +beta check takes ~1min to run but cargo +beta clippy takes ~23mins to run.

There's a Rust 1.57.0 issue (maybe this one) that makes compiling some code really slow. However there's no problem with clippy 0.1.57, only with 0.1.58 so I think this is a clippy issue.

cargo check

This is normal.

time	command
0m56,532s	time cargo +stable check --release --no-default-features --features "std decoder code_asm" --tests
0m52,658s	time cargo +beta check --release --no-default-features --features "std decoder code_asm" --tests

cargo clippy

1.57.0: normal, 1.58.0 (beta): way too slow.

time	command
1m40,849s	time cargo +stable clippy --release --no-default-features --features "std decoder code_asm" --tests
23m26,212s	time cargo +beta clippy --release --no-default-features --features "std decoder code_asm" --tests

• stable: rustc 1.57.0 (f1edd0429 2021-11-29) and clippy 0.1.57 (f1edd04 2021-11-29)
• beta: rustc 1.58.0-beta.2 (0e07bcb68 2021-12-04) and clippy 0.1.58 (0e07bcb 2021-12-04)

Reproducer

git clone https://github.com/icedland/iced.git
cd iced/src/rust/iced-x86
# execute one of the commands above (see the tables)

Version

rustc 1.57.0 (f1edd0429 2021-11-29)
binary: rustc
commit-hash: f1edd0429582dd29cccacaf50fd134b05593bd9c
commit-date: 2021-11-29
host: x86_64-unknown-linux-gnu
release: 1.57.0
LLVM version: 13.0.0

rustc 1.58.0-beta.2 (0e07bcb68 2021-12-04)
binary: rustc
commit-hash: 0e07bcb68b82b54c0c4ec6fe076e9d75b02109cf
commit-date: 2021-12-04
host: x86_64-unknown-linux-gnu
release: 1.58.0-beta.2
LLVM version: 13.0.0

Additional Labels

No response

[llogiq]

Clippy isn't really optimized, however, it might be beneficial to try and collect a profile to see where the time is spent.

[wtfsck]

Using perf, I get:

cargo +stable clippy

Samples: 375K of event 'cycles:u', Event count (approx.): 342320872755
Overhead  Command        Shared Object                        Symbol
   2,78%  rustc          libc.so.6                            [.] _int_malloc
   2,48%  rustc          librustc_driver-15fe7307aff1f259.so  [.] rustc_middle::hir::map::Map::attrs
   1,89%  rustc          libc.so.6                            [.] _int_free
   1,89%  rustc          libc.so.6                            [.] malloc
   1,81%  rustc          libc.so.6                            [.] unlink_chunk.constprop.0
   1,13%  rustc          librustc_driver-15fe7307aff1f259.so  [.] <rustc_lint::late::LateLintPassObjects as rustc_lint::passes::LateLintPass>::exit_lint_attrs
   1,09%  rustc          librustc_driver-15fe7307aff1f259.so  [.] hashbrown::map::RawEntryBuilderMut<K,V,S,A>::from_hash
   1,04%  rustc          libc.so.6                            [.] malloc_consolidate
   1,01%  rustc          librustc_driver-15fe7307aff1f259.so  [.] <rustc_lint::late::LateLintPassObjects as rustc_lint::passes::LateLintPass>::check_expr
   1,00%  rustc          librustc_driver-15fe7307aff1f259.so  [.] rustc_resolve::Resolver::traits_in_module
   1,00%  rustc          libc.so.6                            [.] cfree@GLIBC_2.2.5
   0,97%  rustc          librustc_driver-15fe7307aff1f259.so  [.] <rustc_lint::late::LateLintPassObjects as rustc_lint::passes::LateLintPass>::check_name
   0,93%  rustc          librustc_driver-15fe7307aff1f259.so  [.] <rustc_lint::late::LateLintPassObjects as rustc_lint::passes::LateLintPass>::enter_lint_attrs
   0,90%  rustc          clippy-driver                        [.] rustc_lint::passes::LateLintPass::exit_lint_attrs
   0,84%  rustc          librustc_driver-15fe7307aff1f259.so  [.] rustc_middle::ty::context::TyCtxt::_intern_substs
   0,76%  rustc          librustc_driver-15fe7307aff1f259.so  [.] rustc_span::symbol::Symbol::intern

cargo +beta check

This is here to show that cargo +beta check is much faster than cargo +beta clippy

Samples: 182K of event 'cycles:u', Event count (approx.): 167246634870
Overhead  Command  Shared Object                        Symbol
   2,43%  rustc    rustc                                [.] free
   2,36%  rustc    librustc_driver-6d26630eb1684640.so  [.] <rustc_resolve::Resolver>::traits_in_scope
   1,99%  rustc    rustc                                [.] malloc
   1,87%  rustc    librustc_driver-6d26630eb1684640.so  [.] <hashbrown::map::RawEntryBuilderMut<rustc_middle::ty::context::Interned<rustc_middle::ty::TyS>, (), core::hash::BuildHasherDefault<rustc_hash::FxHasher>>>::from_hash::<hashbrown::map::equivalent<rustc_middle::ty::sty::TyK
   1,46%  rustc    librustc_driver-6d26630eb1684640.so  [.] <rustc_middle::ty::context::TyCtxt>::const_eval_global_id
   1,42%  rustc    librustc_driver-6d26630eb1684640.so  [.] <hashbrown::map::RawEntryBuilderMut<rustc_middle::ty::context::Interned<rustc_middle::ty::PredicateInner>, (), core::hash::BuildHasherDefault<rustc_hash::FxHasher>>>::from_hash::<hashbrown::map::equivalent<rustc_middle::t
   1,41%  rustc    libc.so.6                            [.] __memmove_sse2_unaligned_erms
   1,17%  rustc    librustc_driver-6d26630eb1684640.so  [.] <smallvec::SmallVec<[rustc_mir_build::thir::pattern::deconstruct_pat::Constructor; 1]> as core::iter::traits::collect::Extend<rustc_mir_build::thir::pattern::deconstruct_pat::Constructor>>::extend::<core::iter::adapters::
   1,02%  rustc    librustc_driver-6d26630eb1684640.so  [.] <rustc_middle::hir::map::Map>::body_owner_def_id
   1,00%  rustc    librustc_driver-6d26630eb1684640.so  [.] <rustc_resolve::Resolver as rustc_ast_lowering::ResolverAstLowering>::get_partial_res
   0,93%  rustc    librustc_driver-6d26630eb1684640.so  [.] <rustc_middle::ty::context::CtxtInterners>::intern_ty
   0,90%  rustc    librustc_driver-6d26630eb1684640.so  [.] <core::iter::adapters::map::Map<core::iter::adapters::map::Map<core::iter::adapters::enumerate::Enumerate<core::slice::iter::Iter<rustc_middle::ty::VariantDef>>, <rustc_index::vec::IndexVec<rustc_target::abi::VariantIdx,
   0,83%  rustc    librustc_driver-6d26630eb1684640.so  [.] <rustc_middle::ty::context::TyCtxt>::intern_substs
   0,80%  rustc    librustc_driver-6d26630eb1684640.so  [.] <rustc_typeck::check::fn_ctxt::FnCtxt>::instantiate_value_path
   0,63%  rustc    librustc_driver-6d26630eb1684640.so  [.] <rustc_middle::hir::map::Map>::attrs
   0,61%  rustc    librustc_driver-6d26630eb1684640.so  [.] <rustc_trait_selection::traits::fulfill::FulfillProcessor>::progress_changed_obligations
   0,58%  rustc    librustc_driver-6d26630eb1684640.so  [.] <rustc_borrowck::type_check::TypeChecker>::typeck_mir

cargo +beta clippy

Samples: 5M of event 'cycles:u', Event count (approx.): 4797014161070
Overhead  Command        Shared Object                        Symbol
  53,17%  rustc          clippy-driver                        [.] <rustc_middle::hir::map::Map>::visit_item_likes_in_module::<clippy_utils::VisitConstTestStruct>
  22,99%  rustc          librustc_driver-6d26630eb1684640.so  [.] <rustc_middle::hir::map::Map>::attrs
  15,43%  rustc          librustc_driver-6d26630eb1684640.so  [.] <rustc_middle::hir::map::Map>::item
   0,41%  rustc          librustc_driver-6d26630eb1684640.so  [.] <rustc_middle::hir::map::Map>::impl_item
   0,23%  rustc          libc.so.6                            [.] _int_malloc
   0,17%  rustc          libc.so.6                            [.] malloc
   0,17%  rustc          librustc_driver-6d26630eb1684640.so  [.] <rustc_hir::hir::OwnerNode>::expect_item
   0,15%  rustc          libc.so.6                            [.] unlink_chunk.constprop.0
   0,14%  rustc          libc.so.6                            [.] _int_free
   0,10%  rustc          libc.so.6                            [.] malloc_consolidate
   0,10%  rustc          librustc_driver-6d26630eb1684640.so  [.] <hashbrown::map::RawEntryBuilderMut<rustc_middle::ty::context::Interned<rustc_middle::ty::TyS>, (), core::hash::BuildHasherDefault<rustc_hash::FxHasher>>>::from_hash::<hashbrown::map::equivalent<rustc_middle::ty::st
   0,09%  rustc          librustc_driver-6d26630eb1684640.so  [.] <rustc_resolve::Resolver>::traits_in_scope

• stable = 1.57.0
• beta = 1.58.0

[wtfsck]

clippy_utils::VisitConstTestStruct seems to have been added in this PR: #7811

[llogiq]

Yeah, that's on me. Unfortunately we still don't have a better way to find test items. I should add some caching to recover most of the lost perf.

[llogiq]

@rustbot claim