1 //! This module defines the `DepNode` type which the compiler uses to represent
2 //! nodes in the dependency graph. A `DepNode` consists of a `DepKind` (which
3 //! specifies the kind of thing it represents, like a piece of HIR, MIR, etc)
4 //! and a `Fingerprint`, a 128 bit hash value the exact meaning of which
5 //! depends on the node's `DepKind`. Together, the kind and the fingerprint
6 //! fully identify a dependency node, even across multiple compilation sessions.
7 //! In other words, the value of the fingerprint does not depend on anything
8 //! that is specific to a given compilation session, like an unpredictable
9 //! interning key (e.g., NodeId, DefId, Symbol) or the numeric value of a
10 //! pointer. The concept behind this could be compared to how git commit hashes
11 //! uniquely identify a given commit and has a few advantages:
13 //! * A `DepNode` can simply be serialized to disk and loaded in another session
14 //! without the need to do any "rebasing (like we have to do for Spans and
15 //! NodeIds) or "retracing" like we had to do for `DefId` in earlier
16 //! implementations of the dependency graph.
17 //! * A `Fingerprint` is just a bunch of bits, which allows `DepNode` to
18 //! implement `Copy`, `Sync`, `Send`, `Freeze`, etc.
19 //! * Since we just have a bit pattern, `DepNode` can be mapped from disk into
20 //! memory without any post-processing (e.g., "abomination-style" pointer
22 //! * Because a `DepNode` is self-contained, we can instantiate `DepNodes` that
23 //! refer to things that do not exist anymore. In previous implementations
24 //! `DepNode` contained a `DefId`. A `DepNode` referring to something that
25 //! had been removed between the previous and the current compilation session
26 //! could not be instantiated because the current compilation session
27 //! contained no `DefId` for thing that had been removed.
29 //! `DepNode` definition happens in the `define_dep_nodes!()` macro. This macro
30 //! defines the `DepKind` enum and a corresponding `DepConstructor` enum. The
31 //! `DepConstructor` enum links a `DepKind` to the parameters that are needed at
32 //! runtime in order to construct a valid `DepNode` fingerprint.
34 //! Because the macro sees what parameters a given `DepKind` requires, it can
35 //! "infer" some properties for each kind of `DepNode`:
37 //! * Whether a `DepNode` of a given kind has any parameters at all. Some
38 //! `DepNode`s could represent global concepts with only one value.
39 //! * Whether it is possible, in principle, to reconstruct a query key from a
40 //! given `DepNode`. Many `DepKind`s only require a single `DefId` parameter,
41 //! in which case it is possible to map the node's fingerprint back to the
42 //! `DefId` it was computed from. In other cases, too much information gets
43 //! lost during fingerprint computation.
45 //! The `DepConstructor` enum, together with `DepNode::new()` ensures that only
46 //! valid `DepNode` instances can be constructed. For example, the API does not
47 //! allow for constructing parameterless `DepNode`s with anything other
48 //! than a zeroed out fingerprint. More generally speaking, it relieves the
49 //! user of the `DepNode` API of having to know how to compute the expected
50 //! fingerprint for a given set of node parameters.
52 use crate::mir::interpret::{GlobalId, LitToConstInput};
54 use crate::traits::query::{
55 CanonicalPredicateGoal, CanonicalProjectionGoal, CanonicalTyGoal,
56 CanonicalTypeOpAscribeUserTypeGoal, CanonicalTypeOpEqGoal, CanonicalTypeOpNormalizeGoal,
57 CanonicalTypeOpProvePredicateGoal, CanonicalTypeOpSubtypeGoal,
59 use crate::ty::subst::{GenericArg, SubstsRef};
60 use crate::ty::{self, ParamEnvAnd, Ty, TyCtxt};
62 use rustc_data_structures::fingerprint::Fingerprint;
63 use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, CRATE_DEF_INDEX};
64 use rustc_hir::definitions::DefPathHash;
66 use rustc_span::symbol::Symbol;
69 pub use rustc_query_system::dep_graph::{DepContext, DepNodeParams};
71 // erase!() just makes tokens go away. It's used to specify which macro argument
72 // is repeated (i.e., which sub-expression of the macro we are in) but don't need
73 // to actually use any of the arguments.
78 macro_rules! is_anon_attr {
87 macro_rules! is_eval_always_attr {
96 macro_rules! contains_anon_attr {
97 ($($attr:ident $(($($attr_args:tt)*))* ),*) => ({$(is_anon_attr!($attr) | )* false});
100 macro_rules! contains_eval_always_attr {
101 ($($attr:ident $(($($attr_args:tt)*))* ),*) => ({$(is_eval_always_attr!($attr) | )* false});
104 macro_rules! define_dep_nodes {
108 $variant:ident $(( $tuple_arg_ty:ty $(,)? ))*
111 #[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash,
112 RustcEncodable, RustcDecodable)]
113 #[allow(non_camel_case_types)]
119 #[allow(unreachable_code)]
120 pub fn can_reconstruct_query_key<$tcx>(&self) -> bool {
123 DepKind :: $variant => {
124 if contains_anon_attr!($($attrs)*) {
130 return <$tuple_arg_ty as DepNodeParams<TyCtxt<'_>>>
131 ::can_reconstruct_query_key();
140 pub fn is_anon(&self) -> bool {
143 DepKind :: $variant => { contains_anon_attr!($($attrs)*) }
148 pub fn is_eval_always(&self) -> bool {
151 DepKind :: $variant => { contains_eval_always_attr!($($attrs)*) }
156 #[allow(unreachable_code)]
157 pub fn has_params(&self) -> bool {
160 DepKind :: $variant => {
163 erase!($tuple_arg_ty);
174 pub struct DepConstructor;
176 #[allow(non_camel_case_types)]
177 impl DepConstructor {
180 #[allow(unreachable_code, non_snake_case)]
181 pub fn $variant(_tcx: TyCtxt<'_>, $(arg: $tuple_arg_ty)*) -> DepNode {
184 erase!($tuple_arg_ty);
185 return DepNode::construct(_tcx, DepKind::$variant, &arg)
188 return DepNode::construct(_tcx, DepKind::$variant, &())
193 pub type DepNode = rustc_query_system::dep_graph::DepNode<DepKind>;
195 pub trait DepNodeExt: Sized {
196 /// Construct a DepNode from the given DepKind and DefPathHash. This
197 /// method will assert that the given DepKind actually requires a
198 /// single DefId/DefPathHash parameter.
199 fn from_def_path_hash(def_path_hash: DefPathHash, kind: DepKind) -> Self;
201 /// Extracts the DefId corresponding to this DepNode. This will work
202 /// if two conditions are met:
204 /// 1. The Fingerprint of the DepNode actually is a DefPathHash, and
205 /// 2. the item that the DefPath refers to exists in the current tcx.
207 /// Condition (1) is determined by the DepKind variant of the
208 /// DepNode. Condition (2) might not be fulfilled if a DepNode
209 /// refers to something from the previous compilation session that
210 /// has been removed.
211 fn extract_def_id(&self, tcx: TyCtxt<'_>) -> Option<DefId>;
214 fn from_label_string(label: &str, def_path_hash: DefPathHash)
218 fn has_label_string(label: &str) -> bool;
221 impl DepNodeExt for DepNode {
222 /// Construct a DepNode from the given DepKind and DefPathHash. This
223 /// method will assert that the given DepKind actually requires a
224 /// single DefId/DefPathHash parameter.
225 fn from_def_path_hash(def_path_hash: DefPathHash, kind: DepKind) -> DepNode {
226 debug_assert!(kind.can_reconstruct_query_key() && kind.has_params());
229 hash: def_path_hash.0,
233 /// Extracts the DefId corresponding to this DepNode. This will work
234 /// if two conditions are met:
236 /// 1. The Fingerprint of the DepNode actually is a DefPathHash, and
237 /// 2. the item that the DefPath refers to exists in the current tcx.
239 /// Condition (1) is determined by the DepKind variant of the
240 /// DepNode. Condition (2) might not be fulfilled if a DepNode
241 /// refers to something from the previous compilation session that
242 /// has been removed.
243 fn extract_def_id(&self, tcx: TyCtxt<'tcx>) -> Option<DefId> {
244 if self.kind.can_reconstruct_query_key() {
245 let def_path_hash = DefPathHash(self.hash);
246 tcx.def_path_hash_to_def_id.as_ref()?.get(&def_path_hash).cloned()
253 fn from_label_string(label: &str, def_path_hash: DefPathHash) -> Result<DepNode, ()> {
254 let kind = match label {
256 stringify!($variant) => DepKind::$variant,
261 if !kind.can_reconstruct_query_key() {
265 if kind.has_params() {
266 Ok(DepNode::from_def_path_hash(def_path_hash, kind))
268 Ok(DepNode::new_no_params(kind))
273 fn has_label_string(label: &str) -> bool {
276 stringify!($variant) => true,
283 /// Contains variant => str representations for constructing
284 /// DepNode groups for tests.
285 #[allow(dead_code, non_upper_case_globals)]
288 pub const $variant: &str = stringify!($variant);
294 rustc_dep_node_append!([define_dep_nodes!][ <'tcx>
295 // We use this for most things when incr. comp. is turned off.
298 // Represents metadata from an extern crate.
299 [eval_always] CrateMetadata(CrateNum),
303 [] CompileCodegenUnit(Symbol),
306 impl<'tcx> DepNodeParams<TyCtxt<'tcx>> for DefId {
308 fn can_reconstruct_query_key() -> bool {
312 fn to_fingerprint(&self, tcx: TyCtxt<'tcx>) -> Fingerprint {
313 tcx.def_path_hash(*self).0
316 fn to_debug_str(&self, tcx: TyCtxt<'tcx>) -> String {
317 tcx.def_path_str(*self)
320 fn recover(tcx: TyCtxt<'tcx>, dep_node: &DepNode) -> Option<Self> {
321 dep_node.extract_def_id(tcx)
325 impl<'tcx> DepNodeParams<TyCtxt<'tcx>> for LocalDefId {
327 fn can_reconstruct_query_key() -> bool {
331 fn to_fingerprint(&self, tcx: TyCtxt<'tcx>) -> Fingerprint {
332 self.to_def_id().to_fingerprint(tcx)
335 fn to_debug_str(&self, tcx: TyCtxt<'tcx>) -> String {
336 self.to_def_id().to_debug_str(tcx)
339 fn recover(tcx: TyCtxt<'tcx>, dep_node: &DepNode) -> Option<Self> {
340 dep_node.extract_def_id(tcx).map(|id| id.expect_local())
344 impl<'tcx> DepNodeParams<TyCtxt<'tcx>> for CrateNum {
346 fn can_reconstruct_query_key() -> bool {
350 fn to_fingerprint(&self, tcx: TyCtxt<'tcx>) -> Fingerprint {
351 let def_id = DefId { krate: *self, index: CRATE_DEF_INDEX };
352 tcx.def_path_hash(def_id).0
355 fn to_debug_str(&self, tcx: TyCtxt<'tcx>) -> String {
356 tcx.crate_name(*self).to_string()
359 fn recover(tcx: TyCtxt<'tcx>, dep_node: &DepNode) -> Option<Self> {
360 dep_node.extract_def_id(tcx).map(|id| id.krate)
364 impl<'tcx> DepNodeParams<TyCtxt<'tcx>> for (DefId, DefId) {
366 fn can_reconstruct_query_key() -> bool {
370 // We actually would not need to specialize the implementation of this
371 // method but it's faster to combine the hashes than to instantiate a full
372 // hashing context and stable-hashing state.
373 fn to_fingerprint(&self, tcx: TyCtxt<'tcx>) -> Fingerprint {
374 let (def_id_0, def_id_1) = *self;
376 let def_path_hash_0 = tcx.def_path_hash(def_id_0);
377 let def_path_hash_1 = tcx.def_path_hash(def_id_1);
379 def_path_hash_0.0.combine(def_path_hash_1.0)
382 fn to_debug_str(&self, tcx: TyCtxt<'tcx>) -> String {
383 let (def_id_0, def_id_1) = *self;
385 format!("({}, {})", tcx.def_path_debug_str(def_id_0), tcx.def_path_debug_str(def_id_1))
389 impl<'tcx> DepNodeParams<TyCtxt<'tcx>> for HirId {
391 fn can_reconstruct_query_key() -> bool {
395 // We actually would not need to specialize the implementation of this
396 // method but it's faster to combine the hashes than to instantiate a full
397 // hashing context and stable-hashing state.
398 fn to_fingerprint(&self, tcx: TyCtxt<'tcx>) -> Fingerprint {
399 let HirId { owner, local_id } = *self;
401 let def_path_hash = tcx.def_path_hash(owner.to_def_id());
402 let local_id = Fingerprint::from_smaller_hash(local_id.as_u32().into());
404 def_path_hash.0.combine(local_id)