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Auto merge of #93466 - cjgillot:query-dead, r=nagisa

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Make dead code check a query.

Dead code check is run for each invocation of the compiler, even if no modifications were involved.
This PR makes dead code check a query keyed on the module. This allows to skip the check when a module has not changed.
To perform this, a query `live_symbols_and_ignored_derived_traits` is introduced to encapsulate the global analysis of finding live symbols. The second query `check_mod_deathness` outputs diagnostics for each module based on this first query's results.
This commit is contained in:
bors 2022-02-02 02:29:32 +00:00
commit d5f9c40e6a
5 changed files with 62 additions and 33 deletions
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3
compiler/rustc_interface/src/passes.rs
View file

@ -999,7 +999,8 @@ fn analysis(tcx: TyCtxt<'_>, (): ()) -> Result<()> {
tcx.ensure().check_private_in_public(());
},
{
sess.time("death_checking", || rustc_passes::dead::check_crate(tcx));
tcx.hir()
.par_for_each_module(|module| tcx.ensure().check_mod_deathness(module));
},
{
sess.time("unused_lib_feature_checking", || {

16
compiler/rustc_middle/src/query/mod.rs
View file

@ -758,6 +758,22 @@ rustc_queries! {
desc { |tcx| "checking liveness of variables in {}", describe_as_module(key, tcx) }
}
/// Return the live symbols in the crate for dead code check.
///
/// The second return value maps from ADTs to ignored derived traits (e.g. Debug and Clone) and
/// their respective impl (i.e., part of the derive macro)
query live_symbols_and_ignored_derived_traits(_: ()) -> (
FxHashSet<LocalDefId>,
FxHashMap<LocalDefId, Vec<(DefId, DefId)>>
) {
storage(ArenaCacheSelector<'tcx>)
desc { "find live symbols in crate" }
}
query check_mod_deathness(key: LocalDefId) -> () {
desc { |tcx| "checking deathness of variables in {}", describe_as_module(key, tcx) }
}
query check_mod_impl_wf(key: LocalDefId) -> () {
desc { |tcx| "checking that impls are well-formed in {}", describe_as_module(key, tcx) }
}

55
compiler/rustc_passes/src/dead.rs
View file

@ -13,6 +13,7 @@ use rustc_hir::{Node, PatKind, TyKind};
use rustc_middle::hir::nested_filter;
use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
use rustc_middle::middle::privacy;
use rustc_middle::ty::query::Providers;
use rustc_middle::ty::{self, DefIdTree, TyCtxt};
use rustc_session::lint;
use rustc_span::symbol::{sym, Symbol};
@ -52,7 +53,7 @@ struct MarkSymbolVisitor<'tcx> {
// maps from ADTs to ignored derived traits (e.g. Debug and Clone)
// and the span of their respective impl (i.e., part of the derive
// macro)
ignored_derived_traits: FxHashMap<DefId, Vec<(Span, DefId)>>,
ignored_derived_traits: FxHashMap<LocalDefId, Vec<(DefId, DefId)>>,
}
impl<'tcx> MarkSymbolVisitor<'tcx> {
@ -258,12 +259,11 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
if self.tcx.has_attr(trait_of, sym::rustc_trivial_field_reads) {
let trait_ref = self.tcx.impl_trait_ref(impl_of).unwrap();
if let ty::Adt(adt_def, _) = trait_ref.self_ty().kind() {
let impl_span = self.tcx.def_span(impl_of);
if let Some(v) = self.ignored_derived_traits.get_mut(&adt_def.did) {
v.push((impl_span, trait_of));
} else {
if let Some(adt_def_id) = adt_def.did.as_local() {
self.ignored_derived_traits
.insert(adt_def.did, vec![(impl_span, trait_of)]);
.entry(adt_def_id)
.or_default()
.push((trait_of, impl_of));
}
}
return true;
@ -563,8 +563,8 @@ impl<'v, 'tcx> ItemLikeVisitor<'v> for LifeSeeder<'tcx> {
fn create_and_seed_worklist<'tcx>(
tcx: TyCtxt<'tcx>,
access_levels: &privacy::AccessLevels,
) -> (Vec<LocalDefId>, FxHashMap<LocalDefId, LocalDefId>) {
let access_levels = &tcx.privacy_access_levels(());
let worklist = access_levels
.map
.iter()
@ -584,11 +584,11 @@ fn create_and_seed_worklist<'tcx>(
(life_seeder.worklist, life_seeder.struct_constructors)
}
fn find_live<'tcx>(
fn live_symbols_and_ignored_derived_traits<'tcx>(
tcx: TyCtxt<'tcx>,
access_levels: &privacy::AccessLevels,
) -> (FxHashSet<LocalDefId>, FxHashMap<DefId, Vec<(Span, DefId)>>) {
let (worklist, struct_constructors) = create_and_seed_worklist(tcx, access_levels);
(): (),
) -> (FxHashSet<LocalDefId>, FxHashMap<LocalDefId, Vec<(DefId, DefId)>>) {
let (worklist, struct_constructors) = create_and_seed_worklist(tcx);
let mut symbol_visitor = MarkSymbolVisitor {
worklist,
tcx,
@ -608,8 +608,8 @@ fn find_live<'tcx>(
struct DeadVisitor<'tcx> {
tcx: TyCtxt<'tcx>,
live_symbols: FxHashSet<LocalDefId>,
ignored_derived_traits: FxHashMap<DefId, Vec<(Span, DefId)>>,
live_symbols: &'tcx FxHashSet<LocalDefId>,
ignored_derived_traits: &'tcx FxHashMap<LocalDefId, Vec<(DefId, DefId)>>,
}
impl<'tcx> DeadVisitor<'tcx> {
@ -682,12 +682,10 @@ impl<'tcx> DeadVisitor<'tcx> {
let hir = self.tcx.hir();
if let Some(encl_scope) = hir.get_enclosing_scope(id) {
if let Some(encl_def_id) = hir.opt_local_def_id(encl_scope) {
if let Some(ign_traits) =
self.ignored_derived_traits.get(&encl_def_id.to_def_id())
{
if let Some(ign_traits) = self.ignored_derived_traits.get(&encl_def_id) {
let traits_str = ign_traits
.iter()
.map(|(_, t)| format!("`{}`", self.tcx.item_name(*t)))
.map(|(trait_id, _)| format!("`{}`", self.tcx.item_name(*trait_id)))
.collect::<Vec<_>>()
.join(" and ");
let plural_s = pluralize!(ign_traits.len());
@ -703,7 +701,10 @@ impl<'tcx> DeadVisitor<'tcx> {
traits_str,
is_are
);
let multispan = ign_traits.iter().map(|(s, _)| *s).collect::<Vec<_>>();
let multispan = ign_traits
.iter()
.map(|(_, impl_id)| self.tcx.def_span(*impl_id))
.collect::<Vec<_>>();
err.span_note(multispan, &msg);
}
}
@ -761,6 +762,9 @@ impl<'tcx> Visitor<'tcx> for DeadVisitor<'tcx> {
}
}
// This visitor should only visit a single module at a time.
fn visit_mod(&mut self, _: &'tcx hir::Mod<'tcx>, _: Span, _: hir::HirId) {}
fn visit_variant(
&mut self,
variant: &'tcx hir::Variant<'tcx>,
@ -836,9 +840,16 @@ impl<'tcx> Visitor<'tcx> for DeadVisitor<'tcx> {
}
}
pub fn check_crate(tcx: TyCtxt<'_>) {
let access_levels = &tcx.privacy_access_levels(());
let (live_symbols, ignored_derived_traits) = find_live(tcx, access_levels);
fn check_mod_deathness(tcx: TyCtxt<'_>, module: LocalDefId) {
let (live_symbols, ignored_derived_traits) = tcx.live_symbols_and_ignored_derived_traits(());
let mut visitor = DeadVisitor { tcx, live_symbols, ignored_derived_traits };
tcx.hir().walk_toplevel_module(&mut visitor);
let (module, _, module_id) = tcx.hir().get_module(module);
// Do not use an ItemLikeVisitor since we may want to skip visiting some items
// when a surrounding one is warned against or `_`.
intravisit::walk_mod(&mut visitor, module, module_id);
}
pub(crate) fn provide(providers: &mut Providers) {
*providers =
Providers { live_symbols_and_ignored_derived_traits, check_mod_deathness, ..*providers };
}

1
compiler/rustc_passes/src/lib.rs
View file

@ -45,6 +45,7 @@ mod weak_lang_items;
pub fn provide(providers: &mut Providers) {
check_attr::provide(providers);
check_const::provide(providers);
dead::provide(providers);
diagnostic_items::provide(providers);
entry::provide(providers);
lang_items::provide(providers);

20
src/test/ui/lint/dead-code/lint-dead-code-1.stderr
View file

@ -1,8 +1,8 @@
error: struct is never constructed: `Bar`
--> $DIR/lint-dead-code-1.rs:12:16
error: static is never used: `priv_static`
--> $DIR/lint-dead-code-1.rs:20:1
|
LL | pub struct Bar;
| ^^^
LL | static priv_static: isize = 0;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
note: the lint level is defined here
--> $DIR/lint-dead-code-1.rs:5:9
@ -10,12 +10,6 @@ note: the lint level is defined here
LL | #![deny(dead_code)]
| ^^^^^^^^^
error: static is never used: `priv_static`
--> $DIR/lint-dead-code-1.rs:20:1
|
LL | static priv_static: isize = 0;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: constant is never used: `priv_const`
--> $DIR/lint-dead-code-1.rs:27:1
|
@ -64,5 +58,11 @@ error: function is never used: `baz`
LL | fn baz() -> impl Copy {
| ^^^
error: struct is never constructed: `Bar`
--> $DIR/lint-dead-code-1.rs:12:16
|
LL | pub struct Bar;
| ^^^
error: aborting due to 10 previous errors