Auto merge of #88435 - cjgillot:no-walk-crate, r=Aaron1011

Avoid invoking the hir_crate query to traverse the HIR

Walking the HIR tree is done using the `hir_crate` query. However, this is unnecessary, since `hir_owner(CRATE_DEF_ID)` provides the same information. Since depending on `hir_crate` forces dependents to always be executed, this leads to unnecessary work.

By splitting HIR and attributes visits, we can avoid an edge to `hir_crate` when trying to visit the HIR tree.

Author: bors

compiler/rustc_hir/src/intravisit.rs

@@ -32,7 +32,6 @@
 //! example generator inference, and possibly also HIR borrowck.
 
 use crate::hir::*;
-use crate::hir_id::CRATE_HIR_ID;
 use crate::itemlikevisit::{ItemLikeVisitor, ParItemLikeVisitor};
 use rustc_ast::walk_list;
 use rustc_ast::{Attribute, Label};
@@ -477,17 +476,6 @@ pub trait Visitor<'v>: Sized {
     }
 }
 
-/// Walks the contents of a crate. See also `Crate::visit_all_items`.
-pub fn walk_crate<'v, V: Visitor<'v>>(visitor: &mut V, krate: &'v Crate<'v>) {
-    let top_mod = krate.module();
-    visitor.visit_mod(top_mod, top_mod.inner, CRATE_HIR_ID);
-    for (&id, attrs) in krate.attrs.iter() {
-        for a in *attrs {
-            visitor.visit_attribute(id, a)
-        }
-    }
-}
-
 pub fn walk_mod<'v, V: Visitor<'v>>(visitor: &mut V, module: &'v Mod<'v>, mod_hir_id: HirId) {
     visitor.visit_id(mod_hir_id);
     for &item_id in module.item_ids {

compiler/rustc_incremental/src/persist/dirty_clean.rs

@@ -142,7 +142,7 @@ pub fn check_dirty_clean_annotations(tcx: TyCtxt<'_>) {
         krate.visit_all_item_likes(&mut dirty_clean_visitor);
 
         let mut all_attrs = FindAllAttrs { tcx, found_attrs: vec![] };
-        intravisit::walk_crate(&mut all_attrs, krate);
+        tcx.hir().walk_attributes(&mut all_attrs);
 
         // Note that we cannot use the existing "unused attribute"-infrastructure
         // here, since that is running before codegen. This is also the reason why

compiler/rustc_interface/src/passes.rs

@@ -464,10 +464,6 @@ pub fn lower_to_hir<'res, 'tcx>(
         arena,
     );
 
-    if sess.opts.debugging_opts.hir_stats {
-        hir_stats::print_hir_stats(&hir_crate);
-    }
-
     sess.time("early_lint_checks", || {
         rustc_lint::check_ast_crate(
             sess,

compiler/rustc_lint/src/late.rs

@@ -451,9 +451,8 @@ fn late_lint_pass_crate<'tcx, T: LateLintPass<'tcx>>(tcx: TyCtxt<'tcx>, pass: T)
         // since the root module isn't visited as an item (because it isn't an
         // item), warn for it here.
         lint_callback!(cx, check_crate, krate);
-
-        hir_visit::walk_crate(cx, krate);
-
+        tcx.hir().walk_toplevel_module(cx);
+        tcx.hir().walk_attributes(cx);
         lint_callback!(cx, check_crate_post, krate);
     })
 }

compiler/rustc_lint/src/levels.rs

@@ -37,7 +37,7 @@ fn lint_levels(tcx: TyCtxt<'_>, (): ()) -> LintLevelMap {
 
     let push = builder.levels.push(tcx.hir().attrs(hir::CRATE_HIR_ID), &store, true);
     builder.levels.register_id(hir::CRATE_HIR_ID);
-    intravisit::walk_crate(&mut builder, krate);
+    tcx.hir().walk_toplevel_module(&mut builder);
     builder.levels.pop(push);
 
     builder.levels.build_map()

compiler/rustc_middle/src/hir/map/mod.rs

@@ -7,9 +7,9 @@ use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::svh::Svh;
 use rustc_hir::def::{DefKind, Res};
-use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, CRATE_DEF_INDEX, LOCAL_CRATE};
+use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, CRATE_DEF_ID, CRATE_DEF_INDEX, LOCAL_CRATE};
 use rustc_hir::definitions::{DefKey, DefPath, DefPathHash};
-use rustc_hir::intravisit;
+use rustc_hir::intravisit::{self, Visitor};
 use rustc_hir::itemlikevisit::ItemLikeVisitor;
 use rustc_hir::*;
 use rustc_index::vec::Idx;
@@ -519,6 +519,22 @@ impl<'hir> Map<'hir> {
         }
     }
 
+    /// Walks the contents of a crate. See also `Crate::visit_all_items`.
+    pub fn walk_toplevel_module(self, visitor: &mut impl Visitor<'hir>) {
+        let (top_mod, span, hir_id) = self.get_module(CRATE_DEF_ID);
+        visitor.visit_mod(top_mod, span, hir_id);
+    }
+
+    /// Walks the attributes in a crate.
+    pub fn walk_attributes(self, visitor: &mut impl Visitor<'hir>) {
+        let krate = self.krate();
+        for (&id, attrs) in krate.attrs.iter() {
+            for a in *attrs {
+                visitor.visit_attribute(id, a)
+            }
+        }
+    }
+
     pub fn visit_item_likes_in_module<V>(&self, module: LocalDefId, visitor: &mut V)
     where
         V: ItemLikeVisitor<'hir>,
@@ -934,7 +950,8 @@ pub(super) fn index_hir<'tcx>(tcx: TyCtxt<'tcx>, (): ()) -> &'tcx IndexedHir<'tc
         &tcx.untracked_resolutions.definitions,
         hcx,
     );
-    intravisit::walk_crate(&mut collector, tcx.untracked_crate);
+    let top_mod = tcx.untracked_crate.module();
+    collector.visit_mod(top_mod, top_mod.inner, CRATE_HIR_ID);
 
     let map = collector.finalize_and_compute_crate_hash();
     tcx.arena.alloc(map)

compiler/rustc_passes/src/dead.rs

@@ -775,5 +775,5 @@ pub fn check_crate(tcx: TyCtxt<'_>) {
     let krate = tcx.hir().krate();
     let live_symbols = find_live(tcx, access_levels, krate);
     let mut visitor = DeadVisitor { tcx, live_symbols };
-    intravisit::walk_crate(&mut visitor, krate);
+    tcx.hir().walk_toplevel_module(&mut visitor);
 }

compiler/rustc_passes/src/hir_id_validator.rs

@@ -11,6 +11,10 @@ use rustc_middle::ty::TyCtxt;
 pub fn check_crate(tcx: TyCtxt<'_>) {
     tcx.dep_graph.assert_ignored();
 
+    if tcx.sess.opts.debugging_opts.hir_stats {
+        crate::hir_stats::print_hir_stats(tcx);
+    }
+
     let errors = Lock::new(Vec::new());
     let hir_map = tcx.hir();
 

compiler/rustc_passes/src/hir_stats.rs

@@ -9,6 +9,7 @@ use rustc_hir as hir;
 use rustc_hir::intravisit as hir_visit;
 use rustc_hir::HirId;
 use rustc_middle::hir::map::Map;
+use rustc_middle::ty::TyCtxt;
 use rustc_middle::util::common::to_readable_str;
 use rustc_span::Span;
 
@@ -25,18 +26,19 @@ struct NodeData {
 }
 
 struct StatCollector<'k> {
-    krate: Option<&'k hir::Crate<'k>>,
+    krate: Option<Map<'k>>,
     data: FxHashMap<&'static str, NodeData>,
     seen: FxHashSet<Id>,
 }
 
-pub fn print_hir_stats(krate: &hir::Crate<'_>) {
+pub fn print_hir_stats(tcx: TyCtxt<'_>) {
     let mut collector = StatCollector {
-        krate: Some(krate),
+        krate: Some(tcx.hir()),
         data: FxHashMap::default(),
         seen: FxHashSet::default(),
     };
-    hir_visit::walk_crate(&mut collector, krate);
+    tcx.hir().walk_toplevel_module(&mut collector);
+    tcx.hir().walk_attributes(&mut collector);
     collector.print("HIR STATS");
 }
 

compiler/rustc_passes/src/lib_features.rs

@@ -6,7 +6,7 @@
 
 use rustc_ast::{Attribute, MetaItem, MetaItemKind};
 use rustc_errors::struct_span_err;
-use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
+use rustc_hir::intravisit::{NestedVisitorMap, Visitor};
 use rustc_middle::hir::map::Map;
 use rustc_middle::middle::lib_features::LibFeatures;
 use rustc_middle::ty::query::Providers;
@@ -126,9 +126,7 @@ impl Visitor<'tcx> for LibFeatureCollector<'tcx> {
 
 fn get_lib_features(tcx: TyCtxt<'_>, (): ()) -> LibFeatures {
     let mut collector = LibFeatureCollector::new(tcx);
-    let krate = tcx.hir().krate();
-
-    intravisit::walk_crate(&mut collector, krate);
+    tcx.hir().walk_attributes(&mut collector);
     collector.lib_features
 }