Auto merge of #42504 - michaelwoerister:hash-dep-nodes-prep, r=nikomatsakis

Some preparatory refactorings for hash-based DepNodes

This PR collects some changes that turn out to be necessary for implementing `DepNodes` based on stable hashes (see #42294). The commits are self-contained and mostly straightforward.

The most interesting change here is the introduction of `DefIndices` for things that are not part of the AST: Some pieces of crate metadata now have a `DefIndex` too.

cc @eddyb
r? @nikomatsakis

Author: bors

src/librustc/dep_graph/dep_node.rs

@@ -9,8 +9,10 @@
 // except according to those terms.
 
 use hir::def_id::CrateNum;
+use ich::Fingerprint;
+use rustc_data_structures::stable_hasher::StableHasher;
 use std::fmt::Debug;
-use std::sync::Arc;
+use std::hash::Hash;
 
 macro_rules! try_opt {
     ($e:expr) => (
@@ -51,12 +53,9 @@ pub enum DepNode<D: Clone + Debug> {
     /// in an extern crate.
     MetaData(D),
 
-    /// Represents some piece of metadata global to its crate.
-    GlobalMetaData(D, GlobalMetaDataKind),
-
     /// Represents some artifact that we save to disk. Note that these
     /// do not have a def-id as part of their identifier.
-    WorkProduct(Arc<WorkProductId>),
+    WorkProduct(WorkProductId),
 
     // Represents different phases in the compiler.
     RegionMaps(D),
@@ -307,7 +306,6 @@ impl<D: Clone + Debug> DepNode<D> {
             ItemBodyNestedBodies(ref d) => op(d).map(ItemBodyNestedBodies),
             ConstIsRvaluePromotableToStatic(ref d) => op(d).map(ConstIsRvaluePromotableToStatic),
             IsMirAvailable(ref d) => op(d).map(IsMirAvailable),
-            GlobalMetaData(ref d, kind) => op(d).map(|d| GlobalMetaData(d, kind)),
         }
     }
 }
@@ -318,17 +316,13 @@ impl<D: Clone + Debug> DepNode<D> {
 /// the need to be mapped or unmapped. (This ensures we can serialize
 /// them even in the absence of a tcx.)
 #[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
-pub struct WorkProductId(pub String);
+pub struct WorkProductId(pub Fingerprint);
 
-#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
-pub enum GlobalMetaDataKind {
-    Krate,
-    CrateDeps,
-    DylibDependencyFormats,
-    LangItems,
-    LangItemsMissing,
-    NativeLibraries,
-    CodeMap,
-    Impls,
-    ExportedSymbols,
+impl WorkProductId {
+    pub fn from_cgu_name(cgu_name: &str) -> WorkProductId {
+        let mut hasher = StableHasher::new();
+        cgu_name.len().hash(&mut hasher);
+        cgu_name.hash(&mut hasher);
+        WorkProductId(hasher.finish())
+    }
 }

src/librustc/dep_graph/graph.rs

@@ -13,7 +13,6 @@ use rustc_data_structures::fx::FxHashMap;
 use session::config::OutputType;
 use std::cell::{Ref, RefCell};
 use std::rc::Rc;
-use std::sync::Arc;
 
 use super::dep_node::{DepNode, WorkProductId};
 use super::query::DepGraphQuery;
@@ -35,10 +34,10 @@ struct DepGraphData {
     /// things available to us. If we find that they are not dirty, we
     /// load the path to the file storing those work-products here into
     /// this map. We can later look for and extract that data.
-    previous_work_products: RefCell<FxHashMap<Arc<WorkProductId>, WorkProduct>>,
+    previous_work_products: RefCell<FxHashMap<WorkProductId, WorkProduct>>,
 
     /// Work-products that we generate in this run.
-    work_products: RefCell<FxHashMap<Arc<WorkProductId>, WorkProduct>>,
+    work_products: RefCell<FxHashMap<WorkProductId, WorkProduct>>,
 }
 
 impl DepGraph {
@@ -120,7 +119,7 @@ impl DepGraph {
     /// Indicates that a previous work product exists for `v`. This is
     /// invoked during initial start-up based on what nodes are clean
     /// (and what files exist in the incr. directory).
-    pub fn insert_previous_work_product(&self, v: &Arc<WorkProductId>, data: WorkProduct) {
+    pub fn insert_previous_work_product(&self, v: &WorkProductId, data: WorkProduct) {
         debug!("insert_previous_work_product({:?}, {:?})", v, data);
         self.data.previous_work_products.borrow_mut()
                                         .insert(v.clone(), data);
@@ -129,29 +128,29 @@ impl DepGraph {
     /// Indicates that we created the given work-product in this run
     /// for `v`. This record will be preserved and loaded in the next
     /// run.
-    pub fn insert_work_product(&self, v: &Arc<WorkProductId>, data: WorkProduct) {
+    pub fn insert_work_product(&self, v: &WorkProductId, data: WorkProduct) {
         debug!("insert_work_product({:?}, {:?})", v, data);
         self.data.work_products.borrow_mut()
                                .insert(v.clone(), data);
     }
 
     /// Check whether a previous work product exists for `v` and, if
     /// so, return the path that leads to it. Used to skip doing work.
-    pub fn previous_work_product(&self, v: &Arc<WorkProductId>) -> Option<WorkProduct> {
+    pub fn previous_work_product(&self, v: &WorkProductId) -> Option<WorkProduct> {
         self.data.previous_work_products.borrow()
                                         .get(v)
                                         .cloned()
     }
 
     /// Access the map of work-products created during this run. Only
     /// used during saving of the dep-graph.
-    pub fn work_products(&self) -> Ref<FxHashMap<Arc<WorkProductId>, WorkProduct>> {
+    pub fn work_products(&self) -> Ref<FxHashMap<WorkProductId, WorkProduct>> {
         self.data.work_products.borrow()
     }
 
     /// Access the map of work-products created during the cached run. Only
     /// used during saving of the dep-graph.
-    pub fn previous_work_products(&self) -> Ref<FxHashMap<Arc<WorkProductId>, WorkProduct>> {
+    pub fn previous_work_products(&self) -> Ref<FxHashMap<WorkProductId, WorkProduct>> {
         self.data.previous_work_products.borrow()
     }
 }

src/librustc/dep_graph/mod.rs

@@ -22,7 +22,6 @@ mod thread;
 pub use self::dep_tracking_map::{DepTrackingMap, DepTrackingMapConfig};
 pub use self::dep_node::DepNode;
 pub use self::dep_node::WorkProductId;
-pub use self::dep_node::GlobalMetaDataKind;
 pub use self::graph::DepGraph;
 pub use self::graph::WorkProduct;
 pub use self::query::DepGraphQuery;

src/librustc/hir/map/definitions.rs

@@ -15,7 +15,8 @@
 //! expressions) that are mostly just leftovers.
 
 use hir;
-use hir::def_id::{CrateNum, DefId, DefIndex, LOCAL_CRATE, DefIndexAddressSpace};
+use hir::def_id::{CrateNum, DefId, DefIndex, LOCAL_CRATE, DefIndexAddressSpace,
+                  CRATE_DEF_INDEX};
 use ich::Fingerprint;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::indexed_vec::IndexVec;
@@ -396,6 +397,11 @@ pub enum DefPathData {
     ImplTrait,
     /// A `typeof` type node.
     Typeof,
+
+    /// GlobalMetaData identifies a piece of crate metadata that is global to
+    /// a whole crate (as opposed to just one item). GlobalMetaData components
+    /// are only supposed to show up right below the crate root.
+    GlobalMetaData(Ident)
 }
 
 #[derive(Copy, Clone, Hash, PartialEq, Eq, PartialOrd, Ord, Debug,
@@ -427,8 +433,8 @@ impl Definitions {
 
     /// Get the number of definitions.
     pub fn def_index_counts_lo_hi(&self) -> (usize, usize) {
-        (self.def_index_to_node[DefIndexAddressSpace::Low.index()].len(),
-         self.def_index_to_node[DefIndexAddressSpace::High.index()].len())
+        (self.table.index_to_key[DefIndexAddressSpace::Low.index()].len(),
+         self.table.index_to_key[DefIndexAddressSpace::High.index()].len())
     }
 
     pub fn def_key(&self, index: DefIndex) -> DefKey {
@@ -469,7 +475,12 @@ impl Definitions {
         if def_id.krate == LOCAL_CRATE {
             let space_index = def_id.index.address_space().index();
             let array_index = def_id.index.as_array_index();
-            Some(self.def_index_to_node[space_index][array_index])
+            let node_id = self.def_index_to_node[space_index][array_index];
+            if node_id != ast::DUMMY_NODE_ID {
+                Some(node_id)
+            } else {
+                None
+            }
         } else {
             None
         }
@@ -498,12 +509,16 @@ impl Definitions {
 
         // Create the definition.
         let address_space = super::ITEM_LIKE_SPACE;
-        let index = self.table.allocate(key, def_path_hash, address_space);
+        let root_index = self.table.allocate(key, def_path_hash, address_space);
+        assert_eq!(root_index, CRATE_DEF_INDEX);
         assert!(self.def_index_to_node[address_space.index()].is_empty());
         self.def_index_to_node[address_space.index()].push(ast::CRATE_NODE_ID);
-        self.node_to_def_index.insert(ast::CRATE_NODE_ID, index);
+        self.node_to_def_index.insert(ast::CRATE_NODE_ID, root_index);
 
-        index
+        // Allocate some other DefIndices that always must exist.
+        GlobalMetaDataKind::allocate_def_indices(self);
+
+        root_index
     }
 
     /// Add a definition with a parent definition.
@@ -550,13 +565,19 @@ impl Definitions {
         assert_eq!(index.as_array_index(),
                    self.def_index_to_node[address_space.index()].len());
         self.def_index_to_node[address_space.index()].push(node_id);
+
+        // Some things for which we allocate DefIndices don't correspond to
+        // anything in the AST, so they don't have a NodeId. For these cases
+        // we don't need a mapping from NodeId to DefIndex.
+        if node_id != ast::DUMMY_NODE_ID {
+            debug!("create_def_with_parent: def_index_to_node[{:?} <-> {:?}", index, node_id);
+            self.node_to_def_index.insert(node_id, index);
+        }
+
         if expansion.is_modern() {
             self.expansions.insert(index, expansion);
         }
 
-        debug!("create_def_with_parent: def_index_to_node[{:?} <-> {:?}", index, node_id);
-        self.node_to_def_index.insert(node_id, index);
-
         index
     }
 
@@ -594,7 +615,8 @@ impl DefPathData {
             LifetimeDef(ident) |
             EnumVariant(ident) |
             Binding(ident) |
-            Field(ident) => Some(ident),
+            Field(ident) |
+            GlobalMetaData(ident) => Some(ident),
 
             Impl |
             CrateRoot |
@@ -622,7 +644,8 @@ impl DefPathData {
             LifetimeDef(ident) |
             EnumVariant(ident) |
             Binding(ident) |
-            Field(ident) => {
+            Field(ident) |
+            GlobalMetaData(ident) => {
                 return ident.name.as_str();
             }
 
@@ -667,3 +690,74 @@ impl ::std::hash::Hash for DefPathData {
         }
     }
 }
+
+
+// We define the GlobalMetaDataKind enum with this macro because we want to
+// make sure that we exhaustively iterate over all variants when registering
+// the corresponding DefIndices in the DefTable.
+macro_rules! define_global_metadata_kind {
+    (pub enum GlobalMetaDataKind {
+        $($variant:ident),*
+    }) => (
+        #[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash,
+                 RustcEncodable, RustcDecodable)]
+        pub enum GlobalMetaDataKind {
+            $($variant),*
+        }
+
+        impl GlobalMetaDataKind {
+            fn allocate_def_indices(definitions: &mut Definitions) {
+                $({
+                    let instance = GlobalMetaDataKind::$variant;
+                    definitions.create_def_with_parent(
+                        CRATE_DEF_INDEX,
+                        ast::DUMMY_NODE_ID,
+                        DefPathData::GlobalMetaData(instance.ident()),
+                        DefIndexAddressSpace::High,
+                        Mark::root()
+                    );
+
+                    // Make sure calling def_index does not crash.
+                    instance.def_index(&definitions.table);
+                })*
+            }
+
+            pub fn def_index(&self, def_path_table: &DefPathTable) -> DefIndex {
+                let def_key = DefKey {
+                    parent: Some(CRATE_DEF_INDEX),
+                    disambiguated_data: DisambiguatedDefPathData {
+                        data: DefPathData::GlobalMetaData(self.ident()),
+                        disambiguator: 0,
+                    }
+                };
+
+                def_path_table.key_to_index[&def_key]
+            }
+
+            fn ident(&self) -> Ident {
+
+                let string = match *self {
+                    $(
+                        GlobalMetaDataKind::$variant => {
+                            concat!("{{GlobalMetaData::", stringify!($variant), "}}")
+                        }
+                    )*
+                };
+
+                Ident::from_str(string)
+            }
+        }
+    )
+}
+
+define_global_metadata_kind!(pub enum GlobalMetaDataKind {
+    Krate,
+    CrateDeps,
+    DylibDependencyFormats,
+    LangItems,
+    LangItemsMissing,
+    NativeLibraries,
+    CodeMap,
+    Impls,
+    ExportedSymbols
+});

src/librustc/ich/caching_codemap_view.rs

@@ -29,8 +29,8 @@ pub struct CachingCodemapView<'tcx> {
     time_stamp: usize,
 }
 
-impl<'tcx> CachingCodemapView<'tcx> {
-    pub fn new<'a>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> CachingCodemapView<'tcx> {
+impl<'gcx> CachingCodemapView<'gcx> {
+    pub fn new<'a, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>) -> CachingCodemapView<'gcx> {
         let codemap = tcx.sess.codemap();
         let files = codemap.files();
         let first_file = files[0].clone();