src/librustc/ich/hcx.rs

   1 // Copyright 2017 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use hir;
  12 use hir::def_id::{DefId, DefIndex};
  13 use hir::map::DefPathHash;
  14 use hir::map::definitions::Definitions;
  15 use ich::{self, CachingSourceMapView, Fingerprint};
  16 use middle::cstore::CrateStore;
  17 use ty::{TyCtxt, fast_reject};
  18 use session::Session;
  19
  20 use std::cmp::Ord;
  21 use std::hash as std_hash;
  22 use std::collections::HashMap;
  23 use std::cell::RefCell;
  24
  25 use syntax::ast;
  26
  27 use syntax::source_map::SourceMap;
  28 use syntax::ext::hygiene::SyntaxContext;
  29 use syntax::symbol::Symbol;
  30 use syntax_pos::{Span, DUMMY_SP};
  31 use syntax_pos::hygiene;
  32
  33 use rustc_data_structures::stable_hasher::{HashStable,
  34                                            StableHasher, StableHasherResult,
  35                                            ToStableHashKey};
  36 use rustc_data_structures::fx::{FxHashSet, FxHashMap};
  37 use smallvec::SmallVec;
  38
  39 fn compute_ignored_attr_names() -> FxHashSet<Symbol> {
  40     debug_assert!(ich::IGNORED_ATTRIBUTES.len() > 0);
  41     ich::IGNORED_ATTRIBUTES.iter().map(|&s| Symbol::intern(s)).collect()
  42 }
  43
  44 /// This is the context state available during incr. comp. hashing. It contains
  45 /// enough information to transform DefIds and HirIds into stable DefPaths (i.e.
  46 /// a reference to the TyCtxt) and it holds a few caches for speeding up various
  47 /// things (e.g. each DefId/DefPath is only hashed once).
  48 #[derive(Clone)]
  49 pub struct StableHashingContext<'a> {
  50     sess: &'a Session,
  51     definitions: &'a Definitions,
  52     cstore: &'a dyn CrateStore,
  53     body_resolver: BodyResolver<'a>,
  54     hash_spans: bool,
  55     hash_bodies: bool,
  56     node_id_hashing_mode: NodeIdHashingMode,
  57
  58     // Very often, we are hashing something that does not need the
  59     // CachingSourceMapView, so we initialize it lazily.
  60     raw_source_map: &'a SourceMap,
  61     caching_source_map: Option<CachingSourceMapView<'a>>,
  62 }
  63
  64 #[derive(PartialEq, Eq, Clone, Copy)]
  65 pub enum NodeIdHashingMode {
  66     Ignore,
  67     HashDefPath,
  68 }
  69
  70 /// The BodyResolver allows to map a BodyId to the corresponding hir::Body.
  71 /// We could also just store a plain reference to the hir::Crate but we want
  72 /// to avoid that the crate is used to get untracked access to all of the HIR.
  73 #[derive(Clone, Copy)]
  74 struct BodyResolver<'gcx>(&'gcx hir::Crate);
  75
  76 impl<'gcx> BodyResolver<'gcx> {
  77     // Return a reference to the hir::Body with the given BodyId.
  78     // DOES NOT DO ANY TRACKING, use carefully.
  79     fn body(self, id: hir::BodyId) -> &'gcx hir::Body {
  80         self.0.body(id)
  81     }
  82 }
  83
  84 impl<'a> StableHashingContext<'a> {
  85     // The `krate` here is only used for mapping BodyIds to Bodies.
  86     // Don't use it for anything else or you'll run the risk of
  87     // leaking data out of the tracking system.
  88     pub fn new(sess: &'a Session,
  89                krate: &'a hir::Crate,
  90                definitions: &'a Definitions,
  91                cstore: &'a dyn CrateStore)
  92                -> Self {
  93         let hash_spans_initial = !sess.opts.debugging_opts.incremental_ignore_spans;
  94
  95         StableHashingContext {
  96             sess,
  97             body_resolver: BodyResolver(krate),
  98             definitions,
  99             cstore,
 100             caching_source_map: None,
 101             raw_source_map: sess.source_map(),
 102             hash_spans: hash_spans_initial,
 103             hash_bodies: true,
 104             node_id_hashing_mode: NodeIdHashingMode::HashDefPath,
 105         }
 106     }
 107
 108     #[inline]
 109     pub fn sess(&self) -> &'a Session {
 110         self.sess
 111     }
 112
 113     #[inline]
 114     pub fn while_hashing_hir_bodies<F: FnOnce(&mut Self)>(&mut self,
 115                                                           hash_bodies: bool,
 116                                                           f: F) {
 117         let prev_hash_bodies = self.hash_bodies;
 118         self.hash_bodies = hash_bodies;
 119         f(self);
 120         self.hash_bodies = prev_hash_bodies;
 121     }
 122
 123     #[inline]
 124     pub fn while_hashing_spans<F: FnOnce(&mut Self)>(&mut self,
 125                                                      hash_spans: bool,
 126                                                      f: F) {
 127         let prev_hash_spans = self.hash_spans;
 128         self.hash_spans = hash_spans;
 129         f(self);
 130         self.hash_spans = prev_hash_spans;
 131     }
 132
 133     #[inline]
 134     pub fn with_node_id_hashing_mode<F: FnOnce(&mut Self)>(&mut self,
 135                                                            mode: NodeIdHashingMode,
 136                                                            f: F) {
 137         let prev = self.node_id_hashing_mode;
 138         self.node_id_hashing_mode = mode;
 139         f(self);
 140         self.node_id_hashing_mode = prev;
 141     }
 142
 143     #[inline]
 144     pub fn def_path_hash(&self, def_id: DefId) -> DefPathHash {
 145         if def_id.is_local() {
 146             self.definitions.def_path_hash(def_id.index)
 147         } else {
 148             self.cstore.def_path_hash(def_id)
 149         }
 150     }
 151
 152     #[inline]
 153     pub fn local_def_path_hash(&self, def_index: DefIndex) -> DefPathHash {
 154         self.definitions.def_path_hash(def_index)
 155     }
 156
 157     #[inline]
 158     pub fn node_to_hir_id(&self, node_id: ast::NodeId) -> hir::HirId {
 159         self.definitions.node_to_hir_id(node_id)
 160     }
 161
 162     #[inline]
 163     pub fn hash_bodies(&self) -> bool {
 164         self.hash_bodies
 165     }
 166
 167     #[inline]
 168     pub fn source_map(&mut self) -> &mut CachingSourceMapView<'a> {
 169         match self.caching_source_map {
 170             Some(ref mut cm) => {
 171                 cm
 172             }
 173             ref mut none => {
 174                 *none = Some(CachingSourceMapView::new(self.raw_source_map));
 175                 none.as_mut().unwrap()
 176             }
 177         }
 178     }
 179
 180     #[inline]
 181     pub fn is_ignored_attr(&self, name: Symbol) -> bool {
 182         thread_local! {
 183             static IGNORED_ATTRIBUTES: FxHashSet<Symbol> = compute_ignored_attr_names();
 184         }
 185         IGNORED_ATTRIBUTES.with(|attrs| attrs.contains(&name))
 186     }
 187
 188     pub fn hash_hir_item_like<F: FnOnce(&mut Self)>(&mut self, f: F) {
 189         let prev_hash_node_ids = self.node_id_hashing_mode;
 190         self.node_id_hashing_mode = NodeIdHashingMode::Ignore;
 191
 192         f(self);
 193
 194         self.node_id_hashing_mode = prev_hash_node_ids;
 195     }
 196 }
 197
 198 /// Something that can provide a stable hashing context.
 199 pub trait StableHashingContextProvider<'a> {
 200     fn get_stable_hashing_context(&self) -> StableHashingContext<'a>;
 201 }
 202
 203 impl<'a, 'b, T: StableHashingContextProvider<'a>> StableHashingContextProvider<'a>
 204 for &'b T {
 205     fn get_stable_hashing_context(&self) -> StableHashingContext<'a> {
 206         (**self).get_stable_hashing_context()
 207     }
 208 }
 209
 210 impl<'a, 'b, T: StableHashingContextProvider<'a>> StableHashingContextProvider<'a>
 211 for &'b mut T {
 212     fn get_stable_hashing_context(&self) -> StableHashingContext<'a> {
 213         (**self).get_stable_hashing_context()
 214     }
 215 }
 216
 217 impl<'a, 'gcx, 'lcx> StableHashingContextProvider<'a> for TyCtxt<'a, 'gcx, 'lcx> {
 218     fn get_stable_hashing_context(&self) -> StableHashingContext<'a> {
 219         (*self).create_stable_hashing_context()
 220     }
 221 }
 222
 223 impl<'a> StableHashingContextProvider<'a> for StableHashingContext<'a> {
 224     fn get_stable_hashing_context(&self) -> StableHashingContext<'a> {
 225         self.clone()
 226     }
 227 }
 228
 229 impl<'a> ::dep_graph::DepGraphSafe for StableHashingContext<'a> {
 230 }
 231
 232
 233 impl<'a> HashStable<StableHashingContext<'a>> for hir::BodyId {
 234     fn hash_stable<W: StableHasherResult>(&self,
 235                                           hcx: &mut StableHashingContext<'a>,
 236                                           hasher: &mut StableHasher<W>) {
 237         if hcx.hash_bodies() {
 238             hcx.body_resolver.body(*self).hash_stable(hcx, hasher);
 239         }
 240     }
 241 }
 242
 243 impl<'a> HashStable<StableHashingContext<'a>> for hir::HirId {
 244     #[inline]
 245     fn hash_stable<W: StableHasherResult>(&self,
 246                                           hcx: &mut StableHashingContext<'a>,
 247                                           hasher: &mut StableHasher<W>) {
 248         match hcx.node_id_hashing_mode {
 249             NodeIdHashingMode::Ignore => {
 250                 // Don't do anything.
 251             }
 252             NodeIdHashingMode::HashDefPath => {
 253                 let hir::HirId {
 254                     owner,
 255                     local_id,
 256                 } = *self;
 257
 258                 hcx.local_def_path_hash(owner).hash_stable(hcx, hasher);
 259                 local_id.hash_stable(hcx, hasher);
 260             }
 261         }
 262     }
 263 }
 264
 265 impl<'a> ToStableHashKey<StableHashingContext<'a>> for hir::HirId {
 266     type KeyType = (DefPathHash, hir::ItemLocalId);
 267
 268     #[inline]
 269     fn to_stable_hash_key(&self,
 270                           hcx: &StableHashingContext<'a>)
 271                           -> (DefPathHash, hir::ItemLocalId) {
 272         let def_path_hash = hcx.local_def_path_hash(self.owner);
 273         (def_path_hash, self.local_id)
 274     }
 275 }
 276
 277 impl<'a> HashStable<StableHashingContext<'a>> for ast::NodeId {
 278     fn hash_stable<W: StableHasherResult>(&self,
 279                                           hcx: &mut StableHashingContext<'a>,
 280                                           hasher: &mut StableHasher<W>) {
 281         match hcx.node_id_hashing_mode {
 282             NodeIdHashingMode::Ignore => {
 283                 // Don't do anything.
 284             }
 285             NodeIdHashingMode::HashDefPath => {
 286                 hcx.definitions.node_to_hir_id(*self).hash_stable(hcx, hasher);
 287             }
 288         }
 289     }
 290 }
 291
 292 impl<'a> ToStableHashKey<StableHashingContext<'a>> for ast::NodeId {
 293     type KeyType = (DefPathHash, hir::ItemLocalId);
 294
 295     #[inline]
 296     fn to_stable_hash_key(&self,
 297                           hcx: &StableHashingContext<'a>)
 298                           -> (DefPathHash, hir::ItemLocalId) {
 299         hcx.definitions.node_to_hir_id(*self).to_stable_hash_key(hcx)
 300     }
 301 }
 302
 303 impl<'a> HashStable<StableHashingContext<'a>> for Span {
 304
 305     // Hash a span in a stable way. We can't directly hash the span's BytePos
 306     // fields (that would be similar to hashing pointers, since those are just
 307     // offsets into the SourceMap). Instead, we hash the (file name, line, column)
 308     // triple, which stays the same even if the containing SourceFile has moved
 309     // within the SourceMap.
 310     // Also note that we are hashing byte offsets for the column, not unicode
 311     // codepoint offsets. For the purpose of the hash that's sufficient.
 312     // Also, hashing filenames is expensive so we avoid doing it twice when the
 313     // span starts and ends in the same file, which is almost always the case.
 314     fn hash_stable<W: StableHasherResult>(&self,
 315                                           hcx: &mut StableHashingContext<'a>,
 316                                           hasher: &mut StableHasher<W>) {
 317         const TAG_VALID_SPAN: u8 = 0;
 318         const TAG_INVALID_SPAN: u8 = 1;
 319         const TAG_EXPANSION: u8 = 0;
 320         const TAG_NO_EXPANSION: u8 = 1;
 321
 322         if !hcx.hash_spans {
 323             return
 324         }
 325
 326         if *self == DUMMY_SP {
 327             return std_hash::Hash::hash(&TAG_INVALID_SPAN, hasher);
 328         }
 329
 330         // If this is not an empty or invalid span, we want to hash the last
 331         // position that belongs to it, as opposed to hashing the first
 332         // position past it.
 333         let span = self.data();
 334
 335         if span.hi < span.lo {
 336             return std_hash::Hash::hash(&TAG_INVALID_SPAN, hasher);
 337         }
 338
 339         let (file_lo, line_lo, col_lo) = match hcx.source_map()
 340                                                   .byte_pos_to_line_and_col(span.lo) {
 341             Some(pos) => pos,
 342             None => {
 343                 return std_hash::Hash::hash(&TAG_INVALID_SPAN, hasher);
 344             }
 345         };
 346
 347         if !file_lo.contains(span.hi) {
 348             return std_hash::Hash::hash(&TAG_INVALID_SPAN, hasher);
 349         }
 350
 351         std_hash::Hash::hash(&TAG_VALID_SPAN, hasher);
 352         // We truncate the stable_id hash and line and col numbers. The chances
 353         // of causing a collision this way should be minimal.
 354         std_hash::Hash::hash(&(file_lo.name_hash as u64), hasher);
 355
 356         let col = (col_lo.0 as u64) & 0xFF;
 357         let line = ((line_lo as u64) & 0xFF_FF_FF) << 8;
 358         let len = ((span.hi - span.lo).0 as u64) << 32;
 359         let line_col_len = col | line | len;
 360         std_hash::Hash::hash(&line_col_len, hasher);
 361
 362         if span.ctxt == SyntaxContext::empty() {
 363             TAG_NO_EXPANSION.hash_stable(hcx, hasher);
 364         } else {
 365             TAG_EXPANSION.hash_stable(hcx, hasher);
 366
 367             // Since the same expansion context is usually referenced many
 368             // times, we cache a stable hash of it and hash that instead of
 369             // recursing every time.
 370             thread_local! {
 371                 static CACHE: RefCell<FxHashMap<hygiene::Mark, u64>> =
 372                     RefCell::new(FxHashMap());
 373             }
 374
 375             let sub_hash: u64 = CACHE.with(|cache| {
 376                 let mark = span.ctxt.outer();
 377
 378                 if let Some(&sub_hash) = cache.borrow().get(&mark) {
 379                     return sub_hash;
 380                 }
 381
 382                 let mut hasher = StableHasher::new();
 383                 mark.expn_info().hash_stable(hcx, &mut hasher);
 384                 let sub_hash: Fingerprint = hasher.finish();
 385                 let sub_hash = sub_hash.to_smaller_hash();
 386                 cache.borrow_mut().insert(mark, sub_hash);
 387                 sub_hash
 388             });
 389
 390             sub_hash.hash_stable(hcx, hasher);
 391         }
 392     }
 393 }
 394
 395 pub fn hash_stable_trait_impls<'a, 'gcx, W, R>(
 396     hcx: &mut StableHashingContext<'a>,
 397     hasher: &mut StableHasher<W>,
 398     blanket_impls: &[DefId],
 399     non_blanket_impls: &HashMap<fast_reject::SimplifiedType, Vec<DefId>, R>)
 400     where W: StableHasherResult,
 401           R: std_hash::BuildHasher,
 402 {
 403     {
 404         let mut blanket_impls: SmallVec<[_; 8]> = blanket_impls
 405             .iter()
 406             .map(|&def_id| hcx.def_path_hash(def_id))
 407             .collect();
 408
 409         if blanket_impls.len() > 1 {
 410             blanket_impls.sort_unstable();
 411         }
 412
 413         blanket_impls.hash_stable(hcx, hasher);
 414     }
 415
 416     {
 417         let mut keys: SmallVec<[_; 8]> =
 418             non_blanket_impls.keys()
 419                              .map(|k| (k, k.map_def(|d| hcx.def_path_hash(d))))
 420                              .collect();
 421         keys.sort_unstable_by(|&(_, ref k1), &(_, ref k2)| k1.cmp(k2));
 422         keys.len().hash_stable(hcx, hasher);
 423         for (key, ref stable_key) in keys {
 424             stable_key.hash_stable(hcx, hasher);
 425             let mut impls : SmallVec<[_; 8]> = non_blanket_impls[key]
 426                 .iter()
 427                 .map(|&impl_id| hcx.def_path_hash(impl_id))
 428                 .collect();
 429
 430             if impls.len() > 1 {
 431                 impls.sort_unstable();
 432             }
 433
 434             impls.hash_stable(hcx, hasher);
 435         }
 436     }
 437 }
 438