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ba9703b0 XL |
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: | |
12 | //! | |
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 | |
21 | //! reconstruction). | |
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. | |
28 | //! | |
cdc7bbd5 | 29 | //! `DepNode` definition happens in `rustc_middle` with the `define_dep_nodes!()` macro. |
ba9703b0 XL |
30 | //! This macro defines the `DepKind` enum and a corresponding `DepConstructor` enum. The |
31 | //! `DepConstructor` enum links a `DepKind` to the parameters that are needed at runtime in order | |
32 | //! to construct a valid `DepNode` fingerprint. | |
33 | //! | |
34 | //! Because the macro sees what parameters a given `DepKind` requires, it can | |
35 | //! "infer" some properties for each kind of `DepNode`: | |
36 | //! | |
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. | |
44 | ||
c295e0f8 XL |
45 | use super::{DepContext, DepKind, FingerprintStyle}; |
46 | use crate::ich::StableHashingContext; | |
ba9703b0 | 47 | |
fc512014 | 48 | use rustc_data_structures::fingerprint::{Fingerprint, PackedFingerprint}; |
ba9703b0 | 49 | use rustc_data_structures::stable_hasher::{HashStable, StableHasher}; |
2b03887a | 50 | use rustc_hir::definitions::DefPathHash; |
ba9703b0 XL |
51 | use std::fmt; |
52 | use std::hash::Hash; | |
53 | ||
3dfed10e | 54 | #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Encodable, Decodable)] |
ba9703b0 XL |
55 | pub struct DepNode<K> { |
56 | pub kind: K, | |
fc512014 | 57 | pub hash: PackedFingerprint, |
ba9703b0 XL |
58 | } |
59 | ||
60 | impl<K: DepKind> DepNode<K> { | |
61 | /// Creates a new, parameterless DepNode. This method will assert | |
62 | /// that the DepNode corresponding to the given DepKind actually | |
63 | /// does not require any parameters. | |
3c0e092e XL |
64 | pub fn new_no_params<Ctxt>(tcx: Ctxt, kind: K) -> DepNode<K> |
65 | where | |
66 | Ctxt: super::DepContext<DepKind = K>, | |
67 | { | |
68 | debug_assert_eq!(tcx.fingerprint_style(kind), FingerprintStyle::Unit); | |
fc512014 | 69 | DepNode { kind, hash: Fingerprint::ZERO.into() } |
ba9703b0 | 70 | } |
f9f354fc XL |
71 | |
72 | pub fn construct<Ctxt, Key>(tcx: Ctxt, kind: K, arg: &Key) -> DepNode<K> | |
73 | where | |
6a06907d | 74 | Ctxt: super::DepContext<DepKind = K>, |
f9f354fc XL |
75 | Key: DepNodeParams<Ctxt>, |
76 | { | |
77 | let hash = arg.to_fingerprint(tcx); | |
fc512014 | 78 | let dep_node = DepNode { kind, hash: hash.into() }; |
f9f354fc XL |
79 | |
80 | #[cfg(debug_assertions)] | |
81 | { | |
3c0e092e | 82 | if !tcx.fingerprint_style(kind).reconstructible() |
064997fb FG |
83 | && (tcx.sess().opts.unstable_opts.incremental_info |
84 | || tcx.sess().opts.unstable_opts.query_dep_graph) | |
6a06907d | 85 | { |
f9f354fc XL |
86 | tcx.dep_graph().register_dep_node_debug_str(dep_node, || arg.to_debug_str(tcx)); |
87 | } | |
88 | } | |
89 | ||
90 | dep_node | |
91 | } | |
2b03887a FG |
92 | |
93 | /// Construct a DepNode from the given DepKind and DefPathHash. This | |
94 | /// method will assert that the given DepKind actually requires a | |
95 | /// single DefId/DefPathHash parameter. | |
96 | pub fn from_def_path_hash<Ctxt>(tcx: Ctxt, def_path_hash: DefPathHash, kind: K) -> Self | |
97 | where | |
98 | Ctxt: super::DepContext<DepKind = K>, | |
99 | { | |
100 | debug_assert!(tcx.fingerprint_style(kind) == FingerprintStyle::DefPathHash); | |
101 | DepNode { kind, hash: def_path_hash.0.into() } | |
102 | } | |
ba9703b0 XL |
103 | } |
104 | ||
105 | impl<K: DepKind> fmt::Debug for DepNode<K> { | |
106 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { | |
107 | K::debug_node(self, f) | |
108 | } | |
109 | } | |
110 | ||
111 | pub trait DepNodeParams<Ctxt: DepContext>: fmt::Debug + Sized { | |
c295e0f8 | 112 | fn fingerprint_style() -> FingerprintStyle; |
ba9703b0 XL |
113 | |
114 | /// This method turns the parameters of a DepNodeConstructor into an opaque | |
115 | /// Fingerprint to be used in DepNode. | |
116 | /// Not all DepNodeParams support being turned into a Fingerprint (they | |
117 | /// don't need to if the corresponding DepNode is anonymous). | |
118 | fn to_fingerprint(&self, _: Ctxt) -> Fingerprint { | |
119 | panic!("Not implemented. Accidentally called on anonymous node?") | |
120 | } | |
121 | ||
122 | fn to_debug_str(&self, _: Ctxt) -> String { | |
123 | format!("{:?}", self) | |
124 | } | |
125 | ||
126 | /// This method tries to recover the query key from the given `DepNode`, | |
127 | /// something which is needed when forcing `DepNode`s during red-green | |
128 | /// evaluation. The query system will only call this method if | |
c295e0f8 | 129 | /// `fingerprint_style()` is not `FingerprintStyle::Opaque`. |
ba9703b0 XL |
130 | /// It is always valid to return `None` here, in which case incremental |
131 | /// compilation will treat the query as having changed instead of forcing it. | |
132 | fn recover(tcx: Ctxt, dep_node: &DepNode<Ctxt::DepKind>) -> Option<Self>; | |
133 | } | |
134 | ||
135 | impl<Ctxt: DepContext, T> DepNodeParams<Ctxt> for T | |
136 | where | |
c295e0f8 | 137 | T: for<'a> HashStable<StableHashingContext<'a>> + fmt::Debug, |
ba9703b0 | 138 | { |
3c0e092e | 139 | #[inline(always)] |
c295e0f8 XL |
140 | default fn fingerprint_style() -> FingerprintStyle { |
141 | FingerprintStyle::Opaque | |
f035d41b | 142 | } |
ba9703b0 | 143 | |
3c0e092e | 144 | #[inline(always)] |
ba9703b0 | 145 | default fn to_fingerprint(&self, tcx: Ctxt) -> Fingerprint { |
064997fb FG |
146 | tcx.with_stable_hashing_context(|mut hcx| { |
147 | let mut hasher = StableHasher::new(); | |
148 | self.hash_stable(&mut hcx, &mut hasher); | |
149 | hasher.finish() | |
150 | }) | |
ba9703b0 XL |
151 | } |
152 | ||
3c0e092e | 153 | #[inline(always)] |
ba9703b0 XL |
154 | default fn to_debug_str(&self, _: Ctxt) -> String { |
155 | format!("{:?}", *self) | |
156 | } | |
157 | ||
3c0e092e | 158 | #[inline(always)] |
ba9703b0 XL |
159 | default fn recover(_: Ctxt, _: &DepNode<Ctxt::DepKind>) -> Option<Self> { |
160 | None | |
161 | } | |
162 | } | |
163 | ||
2b03887a FG |
164 | /// This struct stores metadata about each DepKind. |
165 | /// | |
166 | /// Information is retrieved by indexing the `DEP_KINDS` array using the integer value | |
167 | /// of the `DepKind`. Overall, this allows to implement `DepContext` using this manual | |
168 | /// jump table instead of large matches. | |
169 | pub struct DepKindStruct<CTX: DepContext> { | |
170 | /// Anonymous queries cannot be replayed from one compiler invocation to the next. | |
171 | /// When their result is needed, it is recomputed. They are useful for fine-grained | |
172 | /// dependency tracking, and caching within one compiler invocation. | |
173 | pub is_anon: bool, | |
174 | ||
175 | /// Eval-always queries do not track their dependencies, and are always recomputed, even if | |
176 | /// their inputs have not changed since the last compiler invocation. The result is still | |
177 | /// cached within one compiler invocation. | |
178 | pub is_eval_always: bool, | |
179 | ||
180 | /// Whether the query key can be recovered from the hashed fingerprint. | |
181 | /// See [DepNodeParams] trait for the behaviour of each key type. | |
182 | pub fingerprint_style: FingerprintStyle, | |
183 | ||
184 | /// The red/green evaluation system will try to mark a specific DepNode in the | |
185 | /// dependency graph as green by recursively trying to mark the dependencies of | |
186 | /// that `DepNode` as green. While doing so, it will sometimes encounter a `DepNode` | |
187 | /// where we don't know if it is red or green and we therefore actually have | |
188 | /// to recompute its value in order to find out. Since the only piece of | |
189 | /// information that we have at that point is the `DepNode` we are trying to | |
190 | /// re-evaluate, we need some way to re-run a query from just that. This is what | |
191 | /// `force_from_dep_node()` implements. | |
192 | /// | |
193 | /// In the general case, a `DepNode` consists of a `DepKind` and an opaque | |
194 | /// GUID/fingerprint that will uniquely identify the node. This GUID/fingerprint | |
195 | /// is usually constructed by computing a stable hash of the query-key that the | |
196 | /// `DepNode` corresponds to. Consequently, it is not in general possible to go | |
197 | /// back from hash to query-key (since hash functions are not reversible). For | |
198 | /// this reason `force_from_dep_node()` is expected to fail from time to time | |
199 | /// because we just cannot find out, from the `DepNode` alone, what the | |
200 | /// corresponding query-key is and therefore cannot re-run the query. | |
201 | /// | |
202 | /// The system deals with this case letting `try_mark_green` fail which forces | |
203 | /// the root query to be re-evaluated. | |
204 | /// | |
205 | /// Now, if `force_from_dep_node()` would always fail, it would be pretty useless. | |
206 | /// Fortunately, we can use some contextual information that will allow us to | |
207 | /// reconstruct query-keys for certain kinds of `DepNode`s. In particular, we | |
208 | /// enforce by construction that the GUID/fingerprint of certain `DepNode`s is a | |
209 | /// valid `DefPathHash`. Since we also always build a huge table that maps every | |
210 | /// `DefPathHash` in the current codebase to the corresponding `DefId`, we have | |
211 | /// everything we need to re-run the query. | |
212 | /// | |
213 | /// Take the `mir_promoted` query as an example. Like many other queries, it | |
214 | /// just has a single parameter: the `DefId` of the item it will compute the | |
215 | /// validated MIR for. Now, when we call `force_from_dep_node()` on a `DepNode` | |
216 | /// with kind `MirValidated`, we know that the GUID/fingerprint of the `DepNode` | |
217 | /// is actually a `DefPathHash`, and can therefore just look up the corresponding | |
218 | /// `DefId` in `tcx.def_path_hash_to_def_id`. | |
219 | pub force_from_dep_node: Option<fn(tcx: CTX, dep_node: DepNode<CTX::DepKind>) -> bool>, | |
220 | ||
221 | /// Invoke a query to put the on-disk cached value in memory. | |
222 | pub try_load_from_on_disk_cache: Option<fn(CTX, DepNode<CTX::DepKind>)>, | |
223 | } | |
224 | ||
ba9703b0 XL |
225 | /// A "work product" corresponds to a `.o` (or other) file that we |
226 | /// save in between runs. These IDs do not have a `DefId` but rather | |
227 | /// some independent path or string that persists between runs without | |
228 | /// the need to be mapped or unmapped. (This ensures we can serialize | |
229 | /// them even in the absence of a tcx.) | |
3dfed10e XL |
230 | #[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)] |
231 | #[derive(Encodable, Decodable)] | |
ba9703b0 XL |
232 | pub struct WorkProductId { |
233 | hash: Fingerprint, | |
234 | } | |
235 | ||
236 | impl WorkProductId { | |
237 | pub fn from_cgu_name(cgu_name: &str) -> WorkProductId { | |
238 | let mut hasher = StableHasher::new(); | |
ba9703b0 XL |
239 | cgu_name.hash(&mut hasher); |
240 | WorkProductId { hash: hasher.finish() } | |
241 | } | |
ba9703b0 XL |
242 | } |
243 | ||
244 | impl<HCX> HashStable<HCX> for WorkProductId { | |
245 | #[inline] | |
246 | fn hash_stable(&self, hcx: &mut HCX, hasher: &mut StableHasher) { | |
247 | self.hash.hash_stable(hcx, hasher) | |
248 | } | |
249 | } |