Auto merge of #57770 - Zoxc:no-hash-query, r=<try>

Add a query type which is always marked as red if it runs

This is useful for queries which produce results which are very likely to change if their inputs do.

I also expect this to be useful for end to end queries because 1) we don't need `HashStable` impls and 2) we avoid the overhead of hashing the result of large results like the AST or the HIR map.

r? @michaelwoerister

src/librustc/dep_graph/graph.rs

@@ -72,6 +72,16 @@ struct DepGraphData {
     loaded_from_cache: Lock<FxHashMap<DepNodeIndex, bool>>,
 }
 
+pub fn hash_result<R>(hcx: &mut StableHashingContext<'_>, result: &R) -> Option<Fingerprint>
+where
+    R: for<'a> HashStable<StableHashingContext<'a>>,
+{
+    let mut stable_hasher = StableHasher::new();
+    result.hash_stable(hcx, &mut stable_hasher);
+
+    Some(stable_hasher.finish())
+}
+
 impl DepGraph {
 
     pub fn new(prev_graph: PreviousDepGraph,
@@ -169,14 +179,16 @@ impl DepGraph {
     ///   `arg` parameter.
     ///
     /// [rustc guide]: https://rust-lang.github.io/rustc-guide/incremental-compilation.html
-    pub fn with_task<'gcx, C, A, R>(&self,
-                                   key: DepNode,
-                                   cx: C,
-                                   arg: A,
-                                   task: fn(C, A) -> R)
-                                   -> (R, DepNodeIndex)
-        where C: DepGraphSafe + StableHashingContextProvider<'gcx>,
-              R: HashStable<StableHashingContext<'gcx>>,
+    pub fn with_task<'a, C, A, R>(
+        &self,
+        key: DepNode,
+        cx: C,
+        arg: A,
+        task: fn(C, A) -> R,
+        hash_result: impl FnOnce(&mut StableHashingContext<'_>, &R) -> Option<Fingerprint>,
+    ) -> (R, DepNodeIndex)
+    where
+        C: DepGraphSafe + StableHashingContextProvider<'a>,
     {
         self.with_task_impl(key, cx, arg, false, task,
             |_key| Some(TaskDeps {
@@ -187,17 +199,18 @@ impl DepGraph {
             }),
             |data, key, fingerprint, task| {
                 data.borrow_mut().complete_task(key, task.unwrap(), fingerprint)
-            })
+            },
+            hash_result)
     }
 
     /// Creates a new dep-graph input with value `input`
-    pub fn input_task<'gcx, C, R>(&self,
+    pub fn input_task<'a, C, R>(&self,
                                    key: DepNode,
                                    cx: C,
                                    input: R)
                                    -> (R, DepNodeIndex)
-        where C: DepGraphSafe + StableHashingContextProvider<'gcx>,
-              R: HashStable<StableHashingContext<'gcx>>,
+        where C: DepGraphSafe + StableHashingContextProvider<'a>,
+              R: for<'b> HashStable<StableHashingContext<'b>>,
     {
         fn identity_fn<C, A>(_: C, arg: A) -> A {
             arg
@@ -207,10 +220,11 @@ impl DepGraph {
             |_| None,
             |data, key, fingerprint, _| {
                 data.borrow_mut().alloc_node(key, SmallVec::new(), fingerprint)
-            })
+            },
+            hash_result::<R>)
     }
 
-    fn with_task_impl<'gcx, C, A, R>(
+    fn with_task_impl<'a, C, A, R>(
         &self,
         key: DepNode,
         cx: C,
@@ -221,11 +235,11 @@ impl DepGraph {
         finish_task_and_alloc_depnode: fn(&Lock<CurrentDepGraph>,
                                           DepNode,
                                           Fingerprint,
-                                          Option<TaskDeps>) -> DepNodeIndex
+                                          Option<TaskDeps>) -> DepNodeIndex,
+        hash_result: impl FnOnce(&mut StableHashingContext<'_>, &R) -> Option<Fingerprint>,
     ) -> (R, DepNodeIndex)
     where
-        C: DepGraphSafe + StableHashingContextProvider<'gcx>,
-        R: HashStable<StableHashingContext<'gcx>>,
+        C: DepGraphSafe + StableHashingContextProvider<'a>,
     {
         if let Some(ref data) = self.data {
             let task_deps = create_task(key).map(|deps| Lock::new(deps));
@@ -260,31 +274,33 @@ impl DepGraph {
                 profq_msg(hcx.sess(), ProfileQueriesMsg::TaskEnd)
             };
 
-            let mut stable_hasher = StableHasher::new();
-            result.hash_stable(&mut hcx, &mut stable_hasher);
-
-            let current_fingerprint = stable_hasher.finish();
+            let current_fingerprint = hash_result(&mut hcx, &result);
 
             let dep_node_index = finish_task_and_alloc_depnode(
                 &data.current,
                 key,
-                current_fingerprint,
+                current_fingerprint.unwrap_or(Fingerprint::ZERO),
                 task_deps.map(|lock| lock.into_inner()),
             );
 
             // Determine the color of the new DepNode.
             if let Some(prev_index) = data.previous.node_to_index_opt(&key) {
                 let prev_fingerprint = data.previous.fingerprint_by_index(prev_index);
 
-                let color = if current_fingerprint == prev_fingerprint {
-                    DepNodeColor::Green(dep_node_index)
+                let color = if let Some(current_fingerprint) = current_fingerprint {
+                    if current_fingerprint == prev_fingerprint {
+                        DepNodeColor::Green(dep_node_index)
+                    } else {
+                        DepNodeColor::Red
+                    }
                 } else {
+                    // Mark the node as Red if we can't hash the result
                     DepNodeColor::Red
                 };
 
                 debug_assert!(data.colors.get(prev_index).is_none(),
-                              "DepGraph::with_task() - Duplicate DepNodeColor \
-                               insertion for {:?}", key);
+                            "DepGraph::with_task() - Duplicate DepNodeColor \
+                            insertion for {:?}", key);
 
                 data.colors.insert(prev_index, color);
             }
@@ -333,14 +349,16 @@ impl DepGraph {
 
     /// Execute something within an "eval-always" task which is a task
     // that runs whenever anything changes.
-    pub fn with_eval_always_task<'gcx, C, A, R>(&self,
-                                   key: DepNode,
-                                   cx: C,
-                                   arg: A,
-                                   task: fn(C, A) -> R)
-                                   -> (R, DepNodeIndex)
-        where C: DepGraphSafe + StableHashingContextProvider<'gcx>,
-              R: HashStable<StableHashingContext<'gcx>>,
+    pub fn with_eval_always_task<'a, C, A, R>(
+        &self,
+        key: DepNode,
+        cx: C,
+        arg: A,
+        task: fn(C, A) -> R,
+        hash_result: impl FnOnce(&mut StableHashingContext<'_>, &R) -> Option<Fingerprint>,
+    ) -> (R, DepNodeIndex)
+    where
+        C: DepGraphSafe + StableHashingContextProvider<'a>,
     {
         self.with_task_impl(key, cx, arg, false, task,
             |_| None,
@@ -350,7 +368,8 @@ impl DepGraph {
                     &DepNode::new_no_params(DepKind::Krate)
                 ];
                 current.alloc_node(key, smallvec![krate_idx], fingerprint)
-            })
+            },
+            hash_result)
     }
 
     #[inline]

src/librustc/dep_graph/mod.rs

@@ -10,7 +10,7 @@ pub mod cgu_reuse_tracker;
 
 pub use self::dep_tracking_map::{DepTrackingMap, DepTrackingMapConfig};
 pub use self::dep_node::{DepNode, DepKind, DepConstructor, WorkProductId, label_strs};
-pub use self::graph::{DepGraph, WorkProduct, DepNodeIndex, DepNodeColor, TaskDeps};
+pub use self::graph::{DepGraph, WorkProduct, DepNodeIndex, DepNodeColor, TaskDeps, hash_result};
 pub use self::graph::WorkProductFileKind;
 pub use self::prev::PreviousDepGraph;
 pub use self::query::DepGraphQuery;

src/librustc/hir/map/collector.rs

@@ -45,14 +45,14 @@ pub(super) struct NodeCollector<'a, 'hir> {
     hir_body_nodes: Vec<(DefPathHash, Fingerprint)>,
 }
 
-fn input_dep_node_and_hash<'a, I>(
+fn input_dep_node_and_hash<I>(
     dep_graph: &DepGraph,
-    hcx: &mut StableHashingContext<'a>,
+    hcx: &mut StableHashingContext<'_>,
     dep_node: DepNode,
     input: I,
 ) -> (DepNodeIndex, Fingerprint)
 where
-    I: HashStable<StableHashingContext<'a>>,
+    I: for<'a> HashStable<StableHashingContext<'a>>,
 {
     let dep_node_index = dep_graph.input_task(dep_node, &mut *hcx, &input).1;
 
@@ -67,15 +67,15 @@ where
     (dep_node_index, hash)
 }
 
-fn alloc_hir_dep_nodes<'a, I>(
+fn alloc_hir_dep_nodes<I>(
     dep_graph: &DepGraph,
-    hcx: &mut StableHashingContext<'a>,
+    hcx: &mut StableHashingContext<'_>,
     def_path_hash: DefPathHash,
     item_like: I,
     hir_body_nodes: &mut Vec<(DefPathHash, Fingerprint)>,
 ) -> (DepNodeIndex, DepNodeIndex)
 where
-    I: HashStable<StableHashingContext<'a>>,
+    I: for<'a> HashStable<StableHashingContext<'a>>,
 {
     let sig = dep_graph.input_task(
         def_path_hash.to_dep_node(DepKind::Hir),
@@ -280,7 +280,7 @@ impl<'a, 'hir> NodeCollector<'a, 'hir> {
         self.parent_node = parent_node;
     }
 
-    fn with_dep_node_owner<T: HashStable<StableHashingContext<'a>>,
+    fn with_dep_node_owner<T: for<'b> HashStable<StableHashingContext<'b>>,
                            F: FnOnce(&mut Self)>(&mut self,
                                                  dep_node_owner: DefIndex,
                                                  item_like: &T,

src/librustc/ty/context.rs

@@ -1,7 +1,7 @@
 //! type context book-keeping
 
 use dep_graph::DepGraph;
-use dep_graph::{DepNode, DepConstructor};
+use dep_graph::{self, DepNode, DepConstructor};
 use errors::DiagnosticBuilder;
 use session::Session;
 use session::config::{BorrowckMode, OutputFilenames};
@@ -1414,7 +1414,8 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             self.dep_graph.with_task(dep_node,
                                      self,
                                      crate_hash,
-                                     |_, x| x // No transformation needed
+                                     |_, x| x, // No transformation needed
+                                     dep_graph::hash_result,
             );
         }
     }

src/librustc/ty/query/config.rs

@@ -20,7 +20,7 @@ use std::hash::Hash;
 use std::fmt::Debug;
 use syntax_pos::symbol::InternedString;
 use rustc_data_structures::sync::Lock;
-use rustc_data_structures::stable_hasher::HashStable;
+use rustc_data_structures::fingerprint::Fingerprint;
 use ich::StableHashingContext;
 
 // Query configuration and description traits.
@@ -30,7 +30,7 @@ pub trait QueryConfig<'tcx> {
     const CATEGORY: ProfileCategory;
 
     type Key: Eq + Hash + Clone + Debug;
-    type Value: Clone + for<'a> HashStable<StableHashingContext<'a>>;
+    type Value: Clone;
 }
 
 pub(super) trait QueryAccessors<'tcx>: QueryConfig<'tcx> {
@@ -44,6 +44,11 @@ pub(super) trait QueryAccessors<'tcx>: QueryConfig<'tcx> {
     // Don't use this method to compute query results, instead use the methods on TyCtxt
     fn compute(tcx: TyCtxt<'_, 'tcx, '_>, key: Self::Key) -> Self::Value;
 
+    fn hash_result(
+        hcx: &mut StableHashingContext<'_>,
+        result: &Self::Value
+    ) -> Option<Fingerprint>;
+
     fn handle_cycle_error(tcx: TyCtxt<'_, 'tcx, '_>) -> Self::Value;
 }
 

src/librustc/ty/query/mod.rs

@@ -1,4 +1,4 @@
-use dep_graph::{DepConstructor, DepNode};
+use dep_graph::{self, DepConstructor, DepNode};
 use errors::DiagnosticBuilder;
 use hir::def_id::{CrateNum, DefId, DefIndex};
 use hir::def::{Def, Export};
@@ -49,6 +49,7 @@ use rustc_data_structures::indexed_vec::IndexVec;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::stable_hasher::StableVec;
 use rustc_data_structures::sync::Lrc;
+use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_target::spec::PanicStrategy;
 
 use std::borrow::Cow;
@@ -227,15 +228,15 @@ define_queries! { <'tcx>
 
         /// Fetch the MIR for a given def-id right after it's built - this includes
         /// unreachable code.
-        [] fn mir_built: MirBuilt(DefId) -> &'tcx Steal<mir::Mir<'tcx>>,
+        [no_hash] fn mir_built: MirBuilt(DefId) -> &'tcx Steal<mir::Mir<'tcx>>,
 
         /// Fetch the MIR for a given def-id up till the point where it is
         /// ready for const evaluation.
         ///
         /// See the README for the `mir` module for details.
-        [] fn mir_const: MirConst(DefId) -> &'tcx Steal<mir::Mir<'tcx>>,
+        [no_hash] fn mir_const: MirConst(DefId) -> &'tcx Steal<mir::Mir<'tcx>>,
 
-        [] fn mir_validated: MirValidated(DefId) -> &'tcx Steal<mir::Mir<'tcx>>,
+        [no_hash] fn mir_validated: MirValidated(DefId) -> &'tcx Steal<mir::Mir<'tcx>>,
 
         /// MIR after our optimization passes have run. This is MIR that is ready
         /// for codegen. This is also the only query that can fetch non-local MIR, at present.

src/librustc/ty/query/plumbing.rs

@@ -499,7 +499,6 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         dep_node: &DepNode,
         dep_node_index: DepNodeIndex,
     ) {
-        use rustc_data_structures::stable_hasher::{StableHasher, HashStable};
         use ich::Fingerprint;
 
         assert!(Some(self.dep_graph.fingerprint_of(dep_node_index)) ==
@@ -509,11 +508,8 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
 
         debug!("BEGIN verify_ich({:?})", dep_node);
         let mut hcx = self.create_stable_hashing_context();
-        let mut hasher = StableHasher::new();
 
-        result.hash_stable(&mut hcx, &mut hasher);
-
-        let new_hash: Fingerprint = hasher.finish();
+        let new_hash = Q::hash_result(&mut hcx, result).unwrap_or(Fingerprint::ZERO);
         debug!("END verify_ich({:?})", dep_node);
 
         let old_hash = self.dep_graph.fingerprint_of(dep_node_index);
@@ -549,12 +545,14 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
                     tcx.dep_graph.with_eval_always_task(dep_node,
                                                         tcx,
                                                         key,
-                                                        Q::compute)
+                                                        Q::compute,
+                                                        Q::hash_result)
                 } else {
                     tcx.dep_graph.with_task(dep_node,
                                             tcx,
                                             key,
-                                            Q::compute)
+                                            Q::compute,
+                                            Q::hash_result)
                 }
             })
         });
@@ -679,6 +677,18 @@ macro_rules! handle_cycle_error {
     };
 }
 
+macro_rules! hash_result {
+    ([][$hcx:expr, $result:expr]) => {{
+        dep_graph::hash_result($hcx, &$result)
+    }};
+    ([no_hash$(, $modifiers:ident)*][$hcx:expr, $result:expr]) => {{
+        None
+    }};
+    ([$other:ident$(, $modifiers:ident)*][$($args:tt)*]) => {
+        hash_result!([$($modifiers),*][$($args)*])
+    };
+}
+
 macro_rules! define_queries {
     (<$tcx:tt> $($category:tt {
         $($(#[$attr:meta])* [$($modifiers:tt)*] fn $name:ident: $node:ident($K:ty) -> $V:ty,)*
@@ -966,6 +976,13 @@ macro_rules! define_queries_inner {
                 })
             }
 
+            fn hash_result(
+                _hcx: &mut StableHashingContext<'_>,
+                _result: &Self::Value
+            ) -> Option<Fingerprint> {
+                hash_result!([$($modifiers)*][_hcx, _result])
+            }
+
             fn handle_cycle_error(tcx: TyCtxt<'_, 'tcx, '_>) -> Self::Value {
                 handle_cycle_error!([$($modifiers)*][tcx])
             }

src/librustc_codegen_llvm/base.rs

@@ -20,6 +20,7 @@ use super::LlvmCodegenBackend;
 
 use llvm;
 use metadata;
+use rustc::dep_graph;
 use rustc::mir::mono::{Linkage, Visibility, Stats};
 use rustc::middle::cstore::{EncodedMetadata};
 use rustc::ty::TyCtxt;
@@ -145,7 +146,8 @@ pub fn compile_codegen_unit<'ll, 'tcx>(tcx: TyCtxt<'ll, 'tcx, 'tcx>,
     let ((stats, module), _) = tcx.dep_graph.with_task(dep_node,
                                                        tcx,
                                                        cgu_name,
-                                                       module_codegen);
+                                                       module_codegen,
+                                                       dep_graph::hash_result);
     let time_to_codegen = start_time.elapsed();
 
     // We assume that the cost to run LLVM on a CGU is proportional to