Introduce non-incremental queries and load the dep graph with a query

src/librustc/arena.rs

@@ -31,6 +31,7 @@ macro_rules! arena_types {
                 rustc::hir::def_id::DefId,
                 rustc::ty::subst::SubstsRef<$tcx>
             )>,
+            [few] dep_graph: rustc::dep_graph::DepGraph,
             [few] lowered_hir: rustc::hir::LoweredHir,
             [few] hir_map: rustc::hir::map::Map<$tcx>,
             [few, decode] mir_keys: rustc::util::nodemap::DefIdSet,

src/librustc/dep_graph/dep_node.rs

@@ -224,7 +224,7 @@ macro_rules! define_dep_nodes {
                                    (tcx.sess.opts.debugging_opts.incremental_info ||
                                     tcx.sess.opts.debugging_opts.query_dep_graph)
                                 {
-                                    tcx.dep_graph.register_dep_node_debug_str(dep_node, || {
+                                    tcx.dep_graph().register_dep_node_debug_str(dep_node, || {
                                         arg.to_debug_str(tcx)
                                     });
                                 }
@@ -247,7 +247,7 @@ macro_rules! define_dep_nodes {
                                    (tcx.sess.opts.debugging_opts.incremental_info ||
                                     tcx.sess.opts.debugging_opts.query_dep_graph)
                                 {
-                                    tcx.dep_graph.register_dep_node_debug_str(dep_node, || {
+                                    tcx.dep_graph().register_dep_node_debug_str(dep_node, || {
                                         tupled_args.to_debug_str(tcx)
                                     });
                                 }
@@ -368,7 +368,7 @@ impl fmt::Debug for DepNode {
             if let Some(tcx) = opt_tcx {
                 if let Some(def_id) = self.extract_def_id(tcx) {
                     write!(f, "{}", tcx.def_path_debug_str(def_id))?;
-                } else if let Some(ref s) = tcx.dep_graph.dep_node_debug_str(*self) {
+                } else if let Some(ref s) = tcx.dep_graph().dep_node_debug_str(*self) {
                     write!(f, "{}", s)?;
                 } else {
                     write!(f, "{}", self.hash)?;
@@ -402,6 +402,10 @@ rustc_dep_node_append!([define_dep_nodes!][ <'tcx>
     // We use this for most things when incr. comp. is turned off.
     [] Null,
 
+    // Represents all queries which are not incremental.
+    // This is always treated as a red dep node.
+    [] NonIncremental,
+
     // Represents the `Krate` as a whole (the `hir::Krate` value) (as
     // distinct from the krate module). This is basically a hash of
     // the entire krate, so if you read from `Krate` (e.g., by calling
@@ -430,8 +434,6 @@ rustc_dep_node_append!([define_dep_nodes!][ <'tcx>
     [anon] TraitSelect,
 
     [] CompileCodegenUnit(InternedString),
-
-    [eval_always] Analysis(CrateNum),
 ]);
 
 pub trait RecoverKey<'tcx>: Sized {

src/librustc/dep_graph/graph.rs

@@ -20,6 +20,32 @@ use super::safe::DepGraphSafe;
 use super::serialized::{SerializedDepGraph, SerializedDepNodeIndex};
 use super::prev::PreviousDepGraph;
 
+pub type WorkProductMap = FxHashMap<WorkProductId, WorkProduct>;
+
+pub enum LoadResult<T> {
+    Ok { data: T },
+    DataOutOfDate,
+    Error { message: String },
+}
+
+/// Either a result that has already be computed or a
+/// handle that will let us wait until it is computed
+/// by a background thread.
+pub enum MaybeAsync<T> {
+    Sync(T),
+    Async(std::thread::JoinHandle<T>)
+}
+impl<T> MaybeAsync<T> {
+    pub fn open(self) -> std::thread::Result<T> {
+        match self {
+            MaybeAsync::Sync(result) => Ok(result),
+            MaybeAsync::Async(handle) => handle.join()
+        }
+    }
+}
+
+pub type DepGraphFuture = MaybeAsync<LoadResult<(PreviousDepGraph, WorkProductMap)>>;
+
 #[derive(Clone)]
 pub struct DepGraph {
     data: Option<Lrc<DepGraphData>>,
@@ -30,7 +56,7 @@ newtype_index! {
 }
 
 impl DepNodeIndex {
-    const INVALID: DepNodeIndex = DepNodeIndex::MAX;
+    pub(crate) const INVALID: DepNodeIndex = DepNodeIndex::MAX;
 }
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
@@ -94,17 +120,29 @@ impl DepGraph {
                prev_work_products: FxHashMap<WorkProductId, WorkProduct>) -> DepGraph {
         let prev_graph_node_count = prev_graph.node_count();
 
+        let mut data = DepGraphData {
+            previous_work_products: prev_work_products,
+            dep_node_debug: Default::default(),
+            current: Lock::new(CurrentDepGraph::new(prev_graph_node_count)),
+            emitted_diagnostics: Default::default(),
+            emitted_diagnostics_cond_var: Condvar::new(),
+            previous: prev_graph,
+            colors: DepNodeColorMap::new(prev_graph_node_count),
+            loaded_from_cache: Default::default(),
+        };
+
+        let non_incr_dep_node = DepNode::new_no_params(DepKind::NonIncremental);
+
+        // Allocate the NonIncremental node
+        data.current.get_mut().alloc_node(non_incr_dep_node, smallvec![], Fingerprint::ZERO);
+
+        data.previous.node_to_index_opt(&non_incr_dep_node).map(|prev_index| {
+            // Color previous NonIncremental node as red
+            data.colors.insert(prev_index, DepNodeColor::Red);
+        });
+
         DepGraph {
-            data: Some(Lrc::new(DepGraphData {
-                previous_work_products: prev_work_products,
-                dep_node_debug: Default::default(),
-                current: Lock::new(CurrentDepGraph::new(prev_graph_node_count)),
-                emitted_diagnostics: Default::default(),
-                emitted_diagnostics_cond_var: Condvar::new(),
-                previous: prev_graph,
-                colors: DepNodeColorMap::new(prev_graph_node_count),
-                loaded_from_cache: Default::default(),
-            })),
+            data: Some(Lrc::new(data)),
         }
     }
 
@@ -135,18 +173,21 @@ impl DepGraph {
         DepGraphQuery::new(&nodes[..], &edges[..])
     }
 
-    pub fn assert_ignored(&self)
-    {
-        if let Some(..) = self.data {
-            ty::tls::with_context_opt(|icx| {
-                let icx = if let Some(icx) = icx { icx } else { return };
-                assert!(icx.task_deps.is_none(), "expected no task dependency tracking");
-            })
-        }
+    pub fn assert_ignored() {
+        ty::tls::with_context_opt(|icx| {
+            let icx = if let Some(icx) = icx { icx } else { return };
+            assert!(icx.task_deps.is_none(), "expected no task dependency tracking");
+        })
     }
 
     pub fn with_ignore<OP,R>(&self, op: OP) -> R
         where OP: FnOnce() -> R
+    {
+        Self::ignore_deps(op)
+    }
+
+    pub fn ignore_deps<OP,R>(op: OP) -> R
+       where OP: FnOnce() -> R
     {
         ty::tls::with_context(|icx| {
             let icx = ty::tls::ImplicitCtxt {
@@ -394,6 +435,16 @@ impl DepGraph {
             hash_result)
     }
 
+    #[inline]
+    pub fn read_non_incr(tcx: TyCtxt<'_>) {
+        // Avoid loading the `dep_graph` here if we don't need to track dependencies.
+        // We want to load the `dep_graph` in the background.
+        if ty::tls::with_context(|icx| icx.task_deps.is_none()) {
+            return;
+        }
+        tcx.dep_graph().read(DepNode::new_no_params(DepKind::NonIncremental));
+    }
+
     #[inline]
     pub fn read(&self, v: DepNode) {
         if let Some(ref data) = self.data {

src/librustc/dep_graph/mod.rs

@@ -11,7 +11,7 @@ pub mod cgu_reuse_tracker;
 pub use self::dep_tracking_map::{DepTrackingMap, DepTrackingMapConfig};
 pub use self::dep_node::{DepNode, DepKind, DepConstructor, WorkProductId, RecoverKey, label_strs};
 pub use self::graph::{DepGraph, WorkProduct, DepNodeIndex, DepNodeColor, TaskDeps, hash_result};
-pub use self::graph::WorkProductFileKind;
+pub use self::graph::{WorkProductFileKind, DepGraphFuture, LoadResult, WorkProductMap, MaybeAsync};
 pub use self::prev::PreviousDepGraph;
 pub use self::query::DepGraphQuery;
 pub use self::safe::AssertDepGraphSafe;

src/librustc/hir/lowering.rs

@@ -232,14 +232,13 @@ impl<'a> ImplTraitContext<'a> {
 pub fn lower_crate(
     sess: &Session,
     cstore: &dyn CrateStore,
-    dep_graph: &DepGraph,
     krate: &Crate,
     resolver: &mut dyn Resolver,
 ) -> hir::Crate {
     // We're constructing the HIR here; we don't care what we will
     // read, since we haven't even constructed the *input* to
     // incr. comp. yet.
-    dep_graph.assert_ignored();
+    DepGraph::assert_ignored();
 
     LoweringContext {
         crate_root: std_inject::injected_crate_name().map(Symbol::intern),

src/librustc/hir/map/hir_id_validator.rs

@@ -1,11 +1,12 @@
 use crate::hir::def_id::{DefId, DefIndex, CRATE_DEF_INDEX};
 use crate::hir::{self, intravisit, HirId, ItemLocalId};
+use crate::dep_graph::DepGraph;
 use crate::hir::itemlikevisit::ItemLikeVisitor;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::sync::{Lock, ParallelIterator, par_iter};
 
 pub fn check_crate(hir_map: &hir::map::Map<'_>) {
-    hir_map.dep_graph.assert_ignored();
+    DepGraph::assert_ignored();
 
     let errors = Lock::new(Vec::new());
 

src/librustc/hir/map/mod.rs

@@ -1149,7 +1149,7 @@ pub fn map_crate(tcx: TyCtxt<'_>) -> Map<'_> {
         let mut collector = NodeCollector::root(
             tcx.sess,
             krate,
-            &tcx.dep_graph,
+            &tcx.dep_graph(),
             &hir.defs,
             &hir_to_node_id,
             hcx
@@ -1167,7 +1167,7 @@ pub fn map_crate(tcx: TyCtxt<'_>) -> Map<'_> {
 
     let map = Map {
         forest: &hir.forest,
-        dep_graph: tcx.dep_graph.clone(),
+        dep_graph: tcx.dep_graph().clone(),
         crate_hash,
         map,
         hir_to_node_id,

src/librustc/mir/mono.rs

@@ -361,7 +361,7 @@ impl<'tcx> CodegenUnit<'tcx> {
 
     pub fn work_product(&self, tcx: TyCtxt<'_>) -> WorkProduct {
         let work_product_id = self.work_product_id();
-        tcx.dep_graph
+        tcx.dep_graph()
            .previous_work_product(&work_product_id)
            .unwrap_or_else(|| {
                 panic!("Could not find work-product for CGU `{}`", self.name())

src/librustc/query/mod.rs

@@ -31,6 +31,18 @@ use syntax_pos::symbol::InternedString;
 // as they will raise an fatal error on query cycles instead.
 rustc_queries! {
     Other {
+        query dep_graph_future(_: ()) -> Lrc<Steal<Option<DepGraphFuture>>> {
+            no_hash
+            eval_always
+            desc { "loading the dependency graph in the background" }
+        }
+
+        query load_dep_graph(_: ()) -> &'tcx DepGraph {
+            no_hash
+            eval_always
+            desc { "loading the dependency graph" }
+        }
+
         query parse(_: ()) -> Result<Lrc<Steal<ast::Crate>>, ErrorReported> {
             no_hash
             eval_always
@@ -77,6 +89,13 @@ rustc_queries! {
             desc { "indexing HIR" }
         }
 
+        /// Run analysis passes on the crate
+        query analysis(_: CrateNum) -> Result<(), ErrorReported> {
+            no_hash
+            eval_always
+            desc { "running analysis passes on this crate" }
+        }
+
         /// Records the type of every item.
         query type_of(key: DefId) -> Ty<'tcx> {
             cache_on_disk_if { key.is_local() }

src/librustc/traits/select.rs

@@ -1318,10 +1318,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
     where
         OP: FnOnce(&mut Self) -> R,
     {
-        let (result, dep_node) = self.tcx()
-            .dep_graph
-            .with_anon_task(DepKind::TraitSelect, || op(self));
-        self.tcx().dep_graph.read_index(dep_node);
+        let dep_graph = self.tcx().dep_graph();
+        let (result, dep_node) = dep_graph.with_anon_task(DepKind::TraitSelect, || op(self));
+        dep_graph.read_index(dep_node);
         (result, dep_node)
     }
 
@@ -4328,7 +4327,7 @@ impl<T: Clone> WithDepNode<T> {
     }
 
     pub fn get(&self, tcx: TyCtxt<'_>) -> T {
-        tcx.dep_graph.read_index(self.dep_node);
+        tcx.dep_graph().read_index(self.dep_node);
         self.cached_value.clone()
     }
 }