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//! The implementation of the query system itself. This defines the macros that
//! generate the actual methods on tcx which find and execute the provider,
//! manage the caches, and so forth.
use crate::dep_graph::{DepKind, DepNode};
use crate::dep_graph::{DepNodeIndex, SerializedDepNodeIndex};
use crate::query::caches::QueryCache;
use crate::query::config::{QueryDescription, QueryVtable, QueryVtableExt};
use crate::query::job::{QueryInfo, QueryJob, QueryJobId, QueryJobInfo, QueryShardJobId};
use crate::query::{QueryContext, QueryMap};
#[cfg(not(parallel_compiler))]
use rustc_data_structures::cold_path;
use rustc_data_structures::fingerprint::Fingerprint;
use rustc_data_structures::fx::{FxHashMap, FxHasher};
use rustc_data_structures::sharded::Sharded;
use rustc_data_structures::sync::{Lock, LockGuard};
use rustc_data_structures::thin_vec::ThinVec;
use rustc_errors::{Diagnostic, FatalError};
use rustc_span::source_map::DUMMY_SP;
use rustc_span::Span;
use std::collections::hash_map::Entry;
use std::hash::{Hash, Hasher};
use std::mem;
use std::num::NonZeroU32;
use std::ptr;
#[cfg(debug_assertions)]
use std::sync::atomic::{AtomicUsize, Ordering};
pub(super) struct QueryStateShard<D, Q, K, C> {
pub(super) cache: C,
active: FxHashMap<K, QueryResult<D, Q>>,
/// Used to generate unique ids for active jobs.
jobs: u32,
}
impl<D, Q, K, C: Default> Default for QueryStateShard<D, Q, K, C> {
fn default() -> QueryStateShard<D, Q, K, C> {
QueryStateShard { cache: Default::default(), active: Default::default(), jobs: 0 }
}
}
pub struct QueryState<D, Q, C: QueryCache> {
cache: C,
shards: Sharded<QueryStateShard<D, Q, C::Key, C::Sharded>>,
#[cfg(debug_assertions)]
pub cache_hits: AtomicUsize,
}
impl<D, Q, C: QueryCache> QueryState<D, Q, C> {
#[inline]
pub(super) fn get_lookup<'tcx>(
&'tcx self,
key: &C::Key,
) -> QueryLookup<'tcx, D, Q, C::Key, C::Sharded> {
// We compute the key's hash once and then use it for both the
// shard lookup and the hashmap lookup. This relies on the fact
// that both of them use `FxHasher`.
let mut hasher = FxHasher::default();
key.hash(&mut hasher);
let key_hash = hasher.finish();
let shard = self.shards.get_shard_index_by_hash(key_hash);
let lock = self.shards.get_shard_by_index(shard).lock();
QueryLookup { key_hash, shard, lock }
}
}
/// Indicates the state of a query for a given key in a query map.
enum QueryResult<D, Q> {
/// An already executing query. The query job can be used to await for its completion.
Started(QueryJob<D, Q>),
/// The query panicked. Queries trying to wait on this will raise a fatal error which will
/// silently panic.
Poisoned,
}
impl<D, Q, C> QueryState<D, Q, C>
where
D: Copy + Clone + Eq + Hash,
Q: Clone,
C: QueryCache,
{
#[inline(always)]
pub fn iter_results<R>(
&self,
f: impl for<'a> FnOnce(
Box<dyn Iterator<Item = (&'a C::Key, &'a C::Value, DepNodeIndex)> + 'a>,
) -> R,
) -> R {
self.cache.iter(&self.shards, |shard| &mut shard.cache, f)
}
#[inline(always)]
pub fn all_inactive(&self) -> bool {
let shards = self.shards.lock_shards();
shards.iter().all(|shard| shard.active.is_empty())
}
pub fn try_collect_active_jobs(
&self,
kind: D,
make_query: fn(C::Key) -> Q,
jobs: &mut QueryMap<D, Q>,
) -> Option<()> {
// We use try_lock_shards here since we are called from the
// deadlock handler, and this shouldn't be locked.
let shards = self.shards.try_lock_shards()?;
let shards = shards.iter().enumerate();
jobs.extend(shards.flat_map(|(shard_id, shard)| {
shard.active.iter().filter_map(move |(k, v)| {
if let QueryResult::Started(ref job) = *v {
let id = QueryJobId::new(job.id, shard_id, kind);
let info = QueryInfo { span: job.span, query: make_query(k.clone()) };
Some((id, QueryJobInfo { info, job: job.clone() }))
} else {
None
}
})
}));
Some(())
}
}
impl<D, Q, C: QueryCache> Default for QueryState<D, Q, C> {
fn default() -> QueryState<D, Q, C> {
QueryState {
cache: C::default(),
shards: Default::default(),
#[cfg(debug_assertions)]
cache_hits: AtomicUsize::new(0),
}
}
}
/// Values used when checking a query cache which can be reused on a cache-miss to execute the query.
pub struct QueryLookup<'tcx, D, Q, K, C> {
pub(super) key_hash: u64,
shard: usize,
pub(super) lock: LockGuard<'tcx, QueryStateShard<D, Q, K, C>>,
}
/// A type representing the responsibility to execute the job in the `job` field.
/// This will poison the relevant query if dropped.
struct JobOwner<'tcx, D, Q, C>
where
D: Copy + Clone + Eq + Hash,
Q: Clone,
C: QueryCache,
{
state: &'tcx QueryState<D, Q, C>,
key: C::Key,
id: QueryJobId<D>,
}
impl<'tcx, D, Q, C> JobOwner<'tcx, D, Q, C>
where
D: Copy + Clone + Eq + Hash,
Q: Clone,
C: QueryCache,
{
/// Either gets a `JobOwner` corresponding the query, allowing us to
/// start executing the query, or returns with the result of the query.
/// This function assumes that `try_get_cached` is already called and returned `lookup`.
/// If the query is executing elsewhere, this will wait for it and return the result.
/// If the query panicked, this will silently panic.
///
/// This function is inlined because that results in a noticeable speed-up
/// for some compile-time benchmarks.
#[inline(always)]
fn try_start<'a, 'b, CTX>(
tcx: CTX,
state: &'b QueryState<CTX::DepKind, CTX::Query, C>,
span: Span,
key: &C::Key,
mut lookup: QueryLookup<'a, CTX::DepKind, CTX::Query, C::Key, C::Sharded>,
query: &QueryVtable<CTX, C::Key, C::Value>,
) -> TryGetJob<'b, CTX::DepKind, CTX::Query, C>
where
CTX: QueryContext,
{
let lock = &mut *lookup.lock;
let (latch, mut _query_blocked_prof_timer) = match lock.active.entry((*key).clone()) {
Entry::Occupied(mut entry) => {
match entry.get_mut() {
QueryResult::Started(job) => {
// For parallel queries, we'll block and wait until the query running
// in another thread has completed. Record how long we wait in the
// self-profiler.
let _query_blocked_prof_timer = if cfg!(parallel_compiler) {
Some(tcx.profiler().query_blocked())
} else {
None
};
// Create the id of the job we're waiting for
let id = QueryJobId::new(job.id, lookup.shard, query.dep_kind);
(job.latch(id), _query_blocked_prof_timer)
}
QueryResult::Poisoned => FatalError.raise(),
}
}
Entry::Vacant(entry) => {
// No job entry for this query. Return a new one to be started later.
// Generate an id unique within this shard.
let id = lock.jobs.checked_add(1).unwrap();
lock.jobs = id;
let id = QueryShardJobId(NonZeroU32::new(id).unwrap());
let global_id = QueryJobId::new(id, lookup.shard, query.dep_kind);
let job = tcx.current_query_job();
let job = QueryJob::new(id, span, job);
entry.insert(QueryResult::Started(job));
let owner = JobOwner { state, id: global_id, key: (*key).clone() };
return TryGetJob::NotYetStarted(owner);
}
};
mem::drop(lookup.lock);
// If we are single-threaded we know that we have cycle error,
// so we just return the error.
#[cfg(not(parallel_compiler))]
return TryGetJob::Cycle(cold_path(|| {
let error: CycleError<CTX::Query> = latch.find_cycle_in_stack(
tcx.try_collect_active_jobs().unwrap(),
&tcx.current_query_job(),
span,
);
let value = query.handle_cycle_error(tcx, error);
state.cache.store_nocache(value)
}));
// With parallel queries we might just have to wait on some other
// thread.
#[cfg(parallel_compiler)]
{
let result = latch.wait_on(tcx.current_query_job(), span);
if let Err(cycle) = result {
let value = query.handle_cycle_error(tcx, cycle);
let value = state.cache.store_nocache(value);
return TryGetJob::Cycle(value);
}
let cached = try_get_cached(
tcx,
state,
(*key).clone(),
|value, index| (value.clone(), index),
|_, _| panic!("value must be in cache after waiting"),
);
if let Some(prof_timer) = _query_blocked_prof_timer.take() {
prof_timer.finish_with_query_invocation_id(cached.1.into());
}
return TryGetJob::JobCompleted(cached);
}
}
/// 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
#[inline(always)]
fn complete(self, result: C::Value, dep_node_index: DepNodeIndex) -> C::Stored {
// We can move out of `self` here because we `mem::forget` it below
let key = unsafe { ptr::read(&self.key) };
let state = self.state;
// Forget ourself so our destructor won't poison the query
mem::forget(self);
let (job, result) = {
let mut lock = state.shards.get_shard_by_value(&key).lock();
let job = match lock.active.remove(&key).unwrap() {
QueryResult::Started(job) => job,
QueryResult::Poisoned => panic!(),
};
let result = state.cache.complete(&mut lock.cache, key, result, dep_node_index);
(job, result)
};
job.signal_complete();
result
}
}
#[inline(always)]
fn with_diagnostics<F, R>(f: F) -> (R, ThinVec<Diagnostic>)
where
F: FnOnce(Option<&Lock<ThinVec<Diagnostic>>>) -> R,
{
let diagnostics = Lock::new(ThinVec::new());
let result = f(Some(&diagnostics));
(result, diagnostics.into_inner())
}
impl<'tcx, D, Q, C> Drop for JobOwner<'tcx, D, Q, C>
where
D: Copy + Clone + Eq + Hash,
Q: Clone,
C: QueryCache,
{
#[inline(never)]
#[cold]
fn drop(&mut self) {
// Poison the query so jobs waiting on it panic.
let state = self.state;
let shard = state.shards.get_shard_by_value(&self.key);
let job = {
let mut shard = shard.lock();
let job = match shard.active.remove(&self.key).unwrap() {
QueryResult::Started(job) => job,
QueryResult::Poisoned => panic!(),
};
shard.active.insert(self.key.clone(), QueryResult::Poisoned);
job
};
// Also signal the completion of the job, so waiters
// will continue execution.
job.signal_complete();
}
}
#[derive(Clone)]
pub struct CycleError<Q> {
/// The query and related span that uses the cycle.
pub usage: Option<(Span, Q)>,
pub cycle: Vec<QueryInfo<Q>>,
}
/// The result of `try_start`.
enum TryGetJob<'tcx, D, Q, C>
where
D: Copy + Clone + Eq + Hash,
Q: Clone,
C: QueryCache,
{
/// The query is not yet started. Contains a guard to the cache eventually used to start it.
NotYetStarted(JobOwner<'tcx, D, Q, C>),
/// The query was already completed.
/// Returns the result of the query and its dep-node index
/// if it succeeded or a cycle error if it failed.
#[cfg(parallel_compiler)]
JobCompleted((C::Stored, DepNodeIndex)),
/// Trying to execute the query resulted in a cycle.
Cycle(C::Stored),
}
/// Checks if the query is already computed and in the cache.
/// It returns the shard index and a lock guard to the shard,
/// which will be used if the query is not in the cache and we need
/// to compute it.
#[inline(always)]
fn try_get_cached<CTX, C, R, OnHit, OnMiss>(
tcx: CTX,
state: &QueryState<CTX::DepKind, CTX::Query, C>,
key: C::Key,
// `on_hit` can be called while holding a lock to the query cache
on_hit: OnHit,
on_miss: OnMiss,
) -> R
where
C: QueryCache,
CTX: QueryContext,
OnHit: FnOnce(&C::Stored, DepNodeIndex) -> R,
OnMiss: FnOnce(C::Key, QueryLookup<'_, CTX::DepKind, CTX::Query, C::Key, C::Sharded>) -> R,
{
state.cache.lookup(
state,
key,
|value, index| {
if unlikely!(tcx.profiler().enabled()) {
tcx.profiler().query_cache_hit(index.into());
}
#[cfg(debug_assertions)]
{
state.cache_hits.fetch_add(1, Ordering::Relaxed);
}
on_hit(value, index)
},
on_miss,
)
}
#[inline(always)]
fn try_execute_query<CTX, C>(
tcx: CTX,
state: &QueryState<CTX::DepKind, CTX::Query, C>,
span: Span,
key: C::Key,
lookup: QueryLookup<'_, CTX::DepKind, CTX::Query, C::Key, C::Sharded>,
query: &QueryVtable<CTX, C::Key, C::Value>,
) -> C::Stored
where
C: QueryCache,
C::Key: crate::dep_graph::DepNodeParams<CTX>,
CTX: QueryContext,
{
let job = match JobOwner::<'_, CTX::DepKind, CTX::Query, C>::try_start(
tcx, state, span, &key, lookup, query,
) {
TryGetJob::NotYetStarted(job) => job,
TryGetJob::Cycle(result) => return result,
#[cfg(parallel_compiler)]
TryGetJob::JobCompleted((v, index)) => {
tcx.dep_graph().read_index(index);
return v;
}
};
// Fast path for when incr. comp. is off. `to_dep_node` is
// expensive for some `DepKind`s.
if !tcx.dep_graph().is_fully_enabled() {
let null_dep_node = DepNode::new_no_params(DepKind::NULL);
return force_query_with_job(tcx, key, job, null_dep_node, query).0;
}
if query.anon {
let prof_timer = tcx.profiler().query_provider();
let ((result, dep_node_index), diagnostics) = with_diagnostics(|diagnostics| {
tcx.start_query(job.id, diagnostics, |tcx| {
tcx.dep_graph().with_anon_task(query.dep_kind, || query.compute(tcx, key))
})
});
prof_timer.finish_with_query_invocation_id(dep_node_index.into());
tcx.dep_graph().read_index(dep_node_index);
if unlikely!(!diagnostics.is_empty()) {
tcx.store_diagnostics_for_anon_node(dep_node_index, diagnostics);
}
return job.complete(result, dep_node_index);
}
let dep_node = query.to_dep_node(tcx, &key);
if !query.eval_always {
// The diagnostics for this query will be
// promoted to the current session during
// `try_mark_green()`, so we can ignore them here.
let loaded = tcx.start_query(job.id, None, |tcx| {
let marked = tcx.dep_graph().try_mark_green_and_read(tcx, &dep_node);
marked.map(|(prev_dep_node_index, dep_node_index)| {
(
load_from_disk_and_cache_in_memory(
tcx,
key.clone(),
prev_dep_node_index,
dep_node_index,
&dep_node,
query,
),
dep_node_index,
)
})
});
if let Some((result, dep_node_index)) = loaded {
return job.complete(result, dep_node_index);
}
}
let (result, dep_node_index) = force_query_with_job(tcx, key, job, dep_node, query);
tcx.dep_graph().read_index(dep_node_index);
result
}
fn load_from_disk_and_cache_in_memory<CTX, K, V>(
tcx: CTX,
key: K,
prev_dep_node_index: SerializedDepNodeIndex,
dep_node_index: DepNodeIndex,
dep_node: &DepNode<CTX::DepKind>,
query: &QueryVtable<CTX, K, V>,
) -> V
where
CTX: QueryContext,
{
// Note this function can be called concurrently from the same query
// We must ensure that this is handled correctly.
debug_assert!(tcx.dep_graph().is_green(dep_node));
// First we try to load the result from the on-disk cache.
let result = if query.cache_on_disk(tcx, &key, None) {
let prof_timer = tcx.profiler().incr_cache_loading();
let result = query.try_load_from_disk(tcx, prev_dep_node_index);
prof_timer.finish_with_query_invocation_id(dep_node_index.into());
// We always expect to find a cached result for things that
// can be forced from `DepNode`.
debug_assert!(
!dep_node.kind.can_reconstruct_query_key() || result.is_some(),
"missing on-disk cache entry for {:?}",
dep_node
);
result
} else {
// Some things are never cached on disk.
None
};
let result = if let Some(result) = result {
result
} else {
// We could not load a result from the on-disk cache, so
// recompute.
let prof_timer = tcx.profiler().query_provider();
// The dep-graph for this computation is already in-place.
let result = tcx.dep_graph().with_ignore(|| query.compute(tcx, key));
prof_timer.finish_with_query_invocation_id(dep_node_index.into());
result
};
// If `-Zincremental-verify-ich` is specified, re-hash results from
// the cache and make sure that they have the expected fingerprint.
if unlikely!(tcx.incremental_verify_ich()) {
incremental_verify_ich(tcx, &result, dep_node, dep_node_index, query);
}
result
}
#[inline(never)]
#[cold]
fn incremental_verify_ich<CTX, K, V>(
tcx: CTX,
result: &V,
dep_node: &DepNode<CTX::DepKind>,
dep_node_index: DepNodeIndex,
query: &QueryVtable<CTX, K, V>,
) where
CTX: QueryContext,
{
assert!(
Some(tcx.dep_graph().fingerprint_of(dep_node_index))
== tcx.dep_graph().prev_fingerprint_of(dep_node),
"fingerprint for green query instance not loaded from cache: {:?}",
dep_node,
);
debug!("BEGIN verify_ich({:?})", dep_node);
let mut hcx = tcx.create_stable_hashing_context();
let new_hash = query.hash_result(&mut hcx, result).unwrap_or(Fingerprint::ZERO);
debug!("END verify_ich({:?})", dep_node);
let old_hash = tcx.dep_graph().fingerprint_of(dep_node_index);
assert!(new_hash == old_hash, "found unstable fingerprints for {:?}", dep_node,);
}
#[inline(always)]
fn force_query_with_job<C, CTX>(
tcx: CTX,
key: C::Key,
job: JobOwner<'_, CTX::DepKind, CTX::Query, C>,
dep_node: DepNode<CTX::DepKind>,
query: &QueryVtable<CTX, C::Key, C::Value>,
) -> (C::Stored, DepNodeIndex)
where
C: QueryCache,
CTX: QueryContext,
{
// If the following assertion triggers, it can have two reasons:
// 1. Something is wrong with DepNode creation, either here or
// in `DepGraph::try_mark_green()`.
// 2. Two distinct query keys get mapped to the same `DepNode`
// (see for example #48923).
assert!(
!tcx.dep_graph().dep_node_exists(&dep_node),
"forcing query with already existing `DepNode`\n\
- query-key: {:?}\n\
- dep-node: {:?}",
key,
dep_node
);
let prof_timer = tcx.profiler().query_provider();
let ((result, dep_node_index), diagnostics) = with_diagnostics(|diagnostics| {
tcx.start_query(job.id, diagnostics, |tcx| {
if query.eval_always {
tcx.dep_graph().with_eval_always_task(
dep_node,
tcx,
key,
query.compute,
query.hash_result,
)
} else {
tcx.dep_graph().with_task(dep_node, tcx, key, query.compute, query.hash_result)
}
})
});
prof_timer.finish_with_query_invocation_id(dep_node_index.into());
if unlikely!(!diagnostics.is_empty()) {
if dep_node.kind != DepKind::NULL {
tcx.store_diagnostics(dep_node_index, diagnostics);
}
}
let result = job.complete(result, dep_node_index);
(result, dep_node_index)
}
#[inline(never)]
fn get_query_impl<CTX, C>(
tcx: CTX,
state: &QueryState<CTX::DepKind, CTX::Query, C>,
span: Span,
key: C::Key,
query: &QueryVtable<CTX, C::Key, C::Value>,
) -> C::Stored
where
CTX: QueryContext,
C: QueryCache,
C::Key: crate::dep_graph::DepNodeParams<CTX>,
{
try_get_cached(
tcx,
state,
key,
|value, index| {
tcx.dep_graph().read_index(index);
value.clone()
},
|key, lookup| try_execute_query(tcx, state, span, key, lookup, query),
)
}
/// Ensure that either this query has all green inputs or been executed.
/// Executing `query::ensure(D)` is considered a read of the dep-node `D`.
///
/// This function is particularly useful when executing passes for their
/// side-effects -- e.g., in order to report errors for erroneous programs.
///
/// Note: The optimization is only available during incr. comp.
#[inline(never)]
fn ensure_query_impl<CTX, C>(
tcx: CTX,
state: &QueryState<CTX::DepKind, CTX::Query, C>,
key: C::Key,
query: &QueryVtable<CTX, C::Key, C::Value>,
) where
C: QueryCache,
C::Key: crate::dep_graph::DepNodeParams<CTX>,
CTX: QueryContext,
{
if query.eval_always {
let _ = get_query_impl(tcx, state, DUMMY_SP, key, query);
return;
}
// Ensuring an anonymous query makes no sense
assert!(!query.anon);
let dep_node = query.to_dep_node(tcx, &key);
match tcx.dep_graph().try_mark_green_and_read(tcx, &dep_node) {
None => {
// A None return from `try_mark_green_and_read` means that this is either
// a new dep node or that the dep node has already been marked red.
// Either way, we can't call `dep_graph.read()` as we don't have the
// DepNodeIndex. We must invoke the query itself. The performance cost
// this introduces should be negligible as we'll immediately hit the
// in-memory cache, or another query down the line will.
let _ = get_query_impl(tcx, state, DUMMY_SP, key, query);
}
Some((_, dep_node_index)) => {
tcx.profiler().query_cache_hit(dep_node_index.into());
}
}
}
#[inline(never)]
fn force_query_impl<CTX, C>(
tcx: CTX,
state: &QueryState<CTX::DepKind, CTX::Query, C>,
key: C::Key,
span: Span,
dep_node: DepNode<CTX::DepKind>,
query: &QueryVtable<CTX, C::Key, C::Value>,
) where
C: QueryCache,
C::Key: crate::dep_graph::DepNodeParams<CTX>,
CTX: QueryContext,
{
// We may be concurrently trying both execute and force a query.
// Ensure that only one of them runs the query.
try_get_cached(
tcx,
state,
key,
|_, _| {
// Cache hit, do nothing
},
|key, lookup| {
let job = match JobOwner::<'_, CTX::DepKind, CTX::Query, C>::try_start(
tcx, state, span, &key, lookup, query,
) {
TryGetJob::NotYetStarted(job) => job,
TryGetJob::Cycle(_) => return,
#[cfg(parallel_compiler)]
TryGetJob::JobCompleted(_) => return,
};
force_query_with_job(tcx, key, job, dep_node, query);
},
);
}
#[inline(always)]
pub fn get_query<Q, CTX>(tcx: CTX, span: Span, key: Q::Key) -> Q::Stored
where
Q: QueryDescription<CTX>,
Q::Key: crate::dep_graph::DepNodeParams<CTX>,
CTX: QueryContext,
{
debug!("ty::query::get_query<{}>(key={:?}, span={:?})", Q::NAME, key, span);
get_query_impl(tcx, Q::query_state(tcx), span, key, &Q::VTABLE)
}
#[inline(always)]
pub fn ensure_query<Q, CTX>(tcx: CTX, key: Q::Key)
where
Q: QueryDescription<CTX>,
Q::Key: crate::dep_graph::DepNodeParams<CTX>,
CTX: QueryContext,
{
ensure_query_impl(tcx, Q::query_state(tcx), key, &Q::VTABLE)
}
#[inline(always)]
pub fn force_query<Q, CTX>(tcx: CTX, key: Q::Key, span: Span, dep_node: DepNode<CTX::DepKind>)
where
Q: QueryDescription<CTX>,
Q::Key: crate::dep_graph::DepNodeParams<CTX>,
CTX: QueryContext,
{
force_query_impl(tcx, Q::query_state(tcx), key, span, dep_node, &Q::VTABLE)
}