Optimize hash map operations in the query system

Author: Zoxc

compiler/rustc_data_structures/src/lib.rs

@@ -46,6 +46,9 @@ extern crate tracing;
 #[macro_use]
 extern crate rustc_macros;
 
+#[cfg(parallel_compiler)]
+extern crate hashbrown;
+
 use std::fmt;
 
 pub use rustc_index::static_assert_size;

compiler/rustc_data_structures/src/marker.rs

@@ -85,6 +85,7 @@ cfg_match! {
             [std::sync::mpsc::Sender<T> where T: DynSend]
             [std::sync::Arc<T> where T: ?Sized + DynSync + DynSend]
             [std::sync::LazyLock<T, F> where T: DynSend, F: DynSend]
+            [hashbrown::HashTable<T> where T: DynSend]
             [std::collections::HashSet<K, S> where K: DynSend, S: DynSend]
             [std::collections::HashMap<K, V, S> where K: DynSend, V: DynSend, S: DynSend]
             [std::collections::BTreeMap<K, V, A> where K: DynSend, V: DynSend, A: std::alloc::Allocator + Clone + DynSend]

compiler/rustc_query_system/src/lib.rs

@@ -14,6 +14,9 @@ extern crate rustc_data_structures;
 #[macro_use]
 extern crate rustc_macros;
 
+#[allow(unused_extern_crates)]
+extern crate hashbrown;
+
 pub mod cache;
 pub mod dep_graph;
 mod error;

compiler/rustc_query_system/src/query/plumbing.rs

@@ -12,26 +12,30 @@ use crate::query::job::{report_cycle, QueryInfo, QueryJob, QueryJobId, QueryJobI
 use crate::query::SerializedDepNodeIndex;
 use crate::query::{QueryContext, QueryMap, QuerySideEffects, QueryStackFrame};
 use crate::HandleCycleError;
+use hashbrown::hash_table::Entry;
 use rustc_data_structures::fingerprint::Fingerprint;
-use rustc_data_structures::fx::FxHashMap;
-use rustc_data_structures::sharded::Sharded;
+use rustc_data_structures::sharded::{self, Sharded};
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_data_structures::sync::Lock;
 #[cfg(parallel_compiler)]
 use rustc_data_structures::{outline, sync};
 use rustc_errors::{DiagnosticBuilder, FatalError, StashKey};
 use rustc_span::{Span, DUMMY_SP};
 use std::cell::Cell;
-use std::collections::hash_map::Entry;
 use std::fmt::Debug;
 use std::hash::Hash;
 use std::mem;
 use thin_vec::ThinVec;
 
 use super::QueryConfig;
 
+#[inline]
+fn equivalent_key<K: Eq, V>(k: &K) -> impl Fn(&(K, V)) -> bool + '_ {
+    move |x| x.0 == *k
+}
+
 pub struct QueryState<K> {
-    active: Sharded<FxHashMap<K, QueryResult>>,
+    active: Sharded<hashbrown::HashTable<(K, QueryResult)>>,
 }
 
 /// Indicates the state of a query for a given key in a query map.
@@ -165,7 +169,7 @@ where
 {
     /// Completes the query by updating the query cache with the `result`,
     /// signals the waiter and forgets the JobOwner, so it won't poison the query
-    fn complete<C>(self, cache: &C, result: C::Value, dep_node_index: DepNodeIndex)
+    fn complete<C>(self, cache: &C, key_hash: u64, result: C::Value, dep_node_index: DepNodeIndex)
     where
         C: QueryCache<Key = K>,
     {
@@ -180,8 +184,11 @@ where
         cache.complete(key, result, dep_node_index);
 
         let job = {
-            let mut lock = state.active.lock_shard_by_value(&key);
-            lock.remove(&key).unwrap().expect_job()
+            let mut shard = state.active.lock_shard_by_hash(key_hash);
+            match shard.find_entry(key_hash, equivalent_key(&key)) {
+                Err(_) => panic!(),
+                Ok(occupied) => occupied.remove().0.1.expect_job(),
+            }
         };
 
         job.signal_complete();
@@ -198,11 +205,16 @@ where
         // Poison the query so jobs waiting on it panic.
         let state = self.state;
         let job = {
-            let mut shard = state.active.lock_shard_by_value(&self.key);
-            let job = shard.remove(&self.key).unwrap().expect_job();
-
-            shard.insert(self.key, QueryResult::Poisoned);
-            job
+            let key_hash = sharded::make_hash(&self.key);
+            let mut shard = state.active.lock_shard_by_hash(key_hash);
+            match shard.find_entry(key_hash, equivalent_key(&self.key)) {
+                Err(_) => panic!(),
+                Ok(occupied) => {
+                    let ((key, value), vacant) = occupied.remove();
+                    vacant.insert((key, QueryResult::Poisoned));
+                    value.expect_job()
+                }
+            }
         };
         // Also signal the completion of the job, so waiters
         // will continue execution.
@@ -283,12 +295,11 @@ where
                 outline(|| {
                     // We didn't find the query result in the query cache. Check if it was
                     // poisoned due to a panic instead.
-                    let lock = query.query_state(qcx).active.get_shard_by_value(&key).lock();
-
-                    match lock.get(&key) {
-                        Some(QueryResult::Poisoned) => {
-                            panic!("query '{}' not cached due to poisoning", query.name())
-                        }
+                    let key_hash = sharded::make_hash(&key);
+                    let shard = query.query_state(qcx).active.lock_shard_by_hash(key_hash);
+                    match shard.find(key_hash, equivalent_key(&key)) {
+                        // The query we waited on panicked. Continue unwinding here.
+                        Some((_, QueryResult::Poisoned)) => FatalError.raise(),
                         _ => panic!(
                             "query '{}' result must be in the cache or the query must be poisoned after a wait",
                             query.name()
@@ -319,7 +330,8 @@ where
     Qcx: QueryContext,
 {
     let state = query.query_state(qcx);
-    let mut state_lock = state.active.lock_shard_by_value(&key);
+    let key_hash = sharded::make_hash(&key);
+    let mut state_lock = state.active.lock_shard_by_hash(key_hash);
 
     // For the parallel compiler we need to check both the query cache and query state structures
     // while holding the state lock to ensure that 1) the query has not yet completed and 2) the
@@ -336,21 +348,21 @@ where
 
     let current_job_id = qcx.current_query_job();
 
-    match state_lock.entry(key) {
+    match state_lock.entry(key_hash, equivalent_key(&key), |(k, _)| sharded::make_hash(k)) {
         Entry::Vacant(entry) => {
             // Nothing has computed or is computing the query, so we start a new job and insert it in the
             // state map.
             let id = qcx.next_job_id();
             let job = QueryJob::new(id, span, current_job_id);
-            entry.insert(QueryResult::Started(job));
+            entry.insert((key, QueryResult::Started(job)));
 
             // Drop the lock before we start executing the query
             drop(state_lock);
 
-            execute_job::<_, _, INCR>(query, qcx, state, key, id, dep_node)
+            execute_job::<_, _, INCR>(query, qcx, state, key, key_hash, id, dep_node)
         }
         Entry::Occupied(mut entry) => {
-            match entry.get_mut() {
+            match &mut entry.get_mut().1 {
                 QueryResult::Started(job) => {
                     #[cfg(parallel_compiler)]
                     if sync::is_dyn_thread_safe() {
@@ -382,6 +394,7 @@ fn execute_job<Q, Qcx, const INCR: bool>(
     qcx: Qcx,
     state: &QueryState<Q::Key>,
     key: Q::Key,
+    key_hash: u64,
     id: QueryJobId,
     dep_node: Option<DepNode>,
 ) -> (Q::Value, Option<DepNodeIndex>)
@@ -442,7 +455,7 @@ where
             }
         }
     }
-    job_owner.complete(cache, result, dep_node_index);
+    job_owner.complete(cache, key_hash, result, dep_node_index);
 
     (result, Some(dep_node_index))
 }