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::tokenstream::DelimSpan;
  31 use syntax_pos::{Span, DUMMY_SP};
  32 use syntax_pos::hygiene;
  33
  34 use rustc_data_structures::stable_hasher::{HashStable,
  35                                            StableHasher, StableHasherResult,
  36                                            ToStableHashKey};
  37 use rustc_data_structures::fx::{FxHashSet, FxHashMap};
  38 use smallvec::SmallVec;
  39
  40 fn compute_ignored_attr_names() -> FxHashSet<Symbol> {
  41     debug_assert!(ich::IGNORED_ATTRIBUTES.len() > 0);
  42     ich::IGNORED_ATTRIBUTES.iter().map(|&s| Symbol::intern(s)).collect()
  43 }
  44
  45 /// This is the context state available during incr. comp. hashing. It contains
  46 /// enough information to transform DefIds and HirIds into stable DefPaths (i.e.
  47 /// a reference to the TyCtxt) and it holds a few caches for speeding up various
  48 /// things (e.g., each DefId/DefPath is only hashed once).
  49 #[derive(Clone)]
  50 pub struct StableHashingContext<'a> {
  51     sess: &'a Session,
  52     definitions: &'a Definitions,
  53     cstore: &'a dyn CrateStore,
  54     body_resolver: BodyResolver<'a>,
  55     hash_spans: bool,
  56     hash_bodies: bool,
  57     node_id_hashing_mode: NodeIdHashingMode,
  58
  59     // Very often, we are hashing something that does not need the
  60     // CachingSourceMapView, so we initialize it lazily.
  61     raw_source_map: &'a SourceMap,
  62     caching_source_map: Option<CachingSourceMapView<'a>>,
  63 }
  64
  65 #[derive(PartialEq, Eq, Clone, Copy)]
  66 pub enum NodeIdHashingMode {
  67     Ignore,
  68     HashDefPath,
  69 }
  70
  71 /// The BodyResolver allows to map a BodyId to the corresponding hir::Body.
  72 /// We could also just store a plain reference to the hir::Crate but we want
  73 /// to avoid that the crate is used to get untracked access to all of the HIR.
  74 #[derive(Clone, Copy)]
  75 struct BodyResolver<'gcx>(&'gcx hir::Crate);
  76
  77 impl<'gcx> BodyResolver<'gcx> {
  78     // Return a reference to the hir::Body with the given BodyId.
  79     // DOES NOT DO ANY TRACKING, use carefully.
  80     fn body(self, id: hir::BodyId) -> &'gcx hir::Body {
  81         self.0.body(id)
  82     }
  83 }
  84
  85 impl<'a> StableHashingContext<'a> {
  86     // The `krate` here is only used for mapping BodyIds to Bodies.
  87     // Don't use it for anything else or you'll run the risk of
  88     // leaking data out of the tracking system.
  89     pub fn new(sess: &'a Session,
  90                krate: &'a hir::Crate,
  91                definitions: &'a Definitions,
  92                cstore: &'a dyn CrateStore)
  93                -> Self {
  94         let hash_spans_initial = !sess.opts.debugging_opts.incremental_ignore_spans;
  95
  96         StableHashingContext {
  97             sess,
  98             body_resolver: BodyResolver(krate),
  99             definitions,
 100             cstore,
 101             caching_source_map: None,
 102             raw_source_map: sess.source_map(),
 103             hash_spans: hash_spans_initial,
 104             hash_bodies: true,
 105             node_id_hashing_mode: NodeIdHashingMode::HashDefPath,
 106         }
 107     }
 108
 109     #[inline]
 110     pub fn sess(&self) -> &'a Session {
 111         self.sess
 112     }
 113
 114     #[inline]
 115     pub fn while_hashing_hir_bodies<F: FnOnce(&mut Self)>(&mut self,
 116                                                           hash_bodies: bool,
 117                                                           f: F) {
 118         let prev_hash_bodies = self.hash_bodies;
 119         self.hash_bodies = hash_bodies;
 120         f(self);
 121         self.hash_bodies = prev_hash_bodies;
 122     }
 123
 124     #[inline]
 125     pub fn while_hashing_spans<F: FnOnce(&mut Self)>(&mut self,
 126                                                      hash_spans: bool,
 127                                                      f: F) {
 128         let prev_hash_spans = self.hash_spans;
 129         self.hash_spans = hash_spans;
 130         f(self);
 131         self.hash_spans = prev_hash_spans;
 132     }
 133
 134     #[inline]
 135     pub fn with_node_id_hashing_mode<F: FnOnce(&mut Self)>(&mut self,
 136                                                            mode: NodeIdHashingMode,
 137                                                            f: F) {
 138         let prev = self.node_id_hashing_mode;
 139         self.node_id_hashing_mode = mode;
 140         f(self);
 141         self.node_id_hashing_mode = prev;
 142     }
 143
 144     #[inline]
 145     pub fn def_path_hash(&self, def_id: DefId) -> DefPathHash {
 146         if def_id.is_local() {
 147             self.definitions.def_path_hash(def_id.index)
 148         } else {
 149             self.cstore.def_path_hash(def_id)
 150         }
 151     }
 152
 153     #[inline]
 154     pub fn local_def_path_hash(&self, def_index: DefIndex) -> DefPathHash {
 155         self.definitions.def_path_hash(def_index)
 156     }
 157
 158     #[inline]
 159     pub fn node_to_hir_id(&self, node_id: ast::NodeId) -> hir::HirId {
 160         self.definitions.node_to_hir_id(node_id)
 161     }
 162
 163     #[inline]
 164     pub fn hash_bodies(&self) -> bool {
 165         self.hash_bodies
 166     }
 167
 168     #[inline]
 169     pub fn source_map(&mut self) -> &mut CachingSourceMapView<'a> {
 170         match self.caching_source_map {
 171             Some(ref mut cm) => {
 172                 cm
 173             }
 174             ref mut none => {
 175                 *none = Some(CachingSourceMapView::new(self.raw_source_map));
 176                 none.as_mut().unwrap()
 177             }
 178         }
 179     }
 180
 181     #[inline]
 182     pub fn is_ignored_attr(&self, name: Symbol) -> bool {
 183         thread_local! {
 184             static IGNORED_ATTRIBUTES: FxHashSet<Symbol> = compute_ignored_attr_names();
 185         }
 186         IGNORED_ATTRIBUTES.with(|attrs| attrs.contains(&name))
 187     }
 188
 189     pub fn hash_hir_item_like<F: FnOnce(&mut Self)>(&mut self, f: F) {
 190         let prev_hash_node_ids = self.node_id_hashing_mode;
 191         self.node_id_hashing_mode = NodeIdHashingMode::Ignore;
 192
 193         f(self);
 194
 195         self.node_id_hashing_mode = prev_hash_node_ids;
 196     }
 197 }
 198
 199 /// Something that can provide a stable hashing context.
 200 pub trait StableHashingContextProvider<'a> {
 201     fn get_stable_hashing_context(&self) -> StableHashingContext<'a>;
 202 }
 203
 204 impl<'a, 'b, T: StableHashingContextProvider<'a>> StableHashingContextProvider<'a>
 205 for &'b T {
 206     fn get_stable_hashing_context(&self) -> StableHashingContext<'a> {
 207         (**self).get_stable_hashing_context()
 208     }
 209 }
 210
 211 impl<'a, 'b, T: StableHashingContextProvider<'a>> StableHashingContextProvider<'a>
 212 for &'b mut T {
 213     fn get_stable_hashing_context(&self) -> StableHashingContext<'a> {
 214         (**self).get_stable_hashing_context()
 215     }
 216 }
 217
 218 impl<'a, 'gcx, 'lcx> StableHashingContextProvider<'a> for TyCtxt<'a, 'gcx, 'lcx> {
 219     fn get_stable_hashing_context(&self) -> StableHashingContext<'a> {
 220         (*self).create_stable_hashing_context()
 221     }
 222 }
 223
 224 impl<'a> StableHashingContextProvider<'a> for StableHashingContext<'a> {
 225     fn get_stable_hashing_context(&self) -> StableHashingContext<'a> {
 226         self.clone()
 227     }
 228 }
 229
 230 impl<'a> ::dep_graph::DepGraphSafe for StableHashingContext<'a> {
 231 }
 232
 233
 234 impl<'a> HashStable<StableHashingContext<'a>> for hir::BodyId {
 235     fn hash_stable<W: StableHasherResult>(&self,
 236                                           hcx: &mut StableHashingContext<'a>,
 237                                           hasher: &mut StableHasher<W>) {
 238         if hcx.hash_bodies() {
 239             hcx.body_resolver.body(*self).hash_stable(hcx, hasher);
 240         }
 241     }
 242 }
 243
 244 impl<'a> HashStable<StableHashingContext<'a>> for hir::HirId {
 245     #[inline]
 246     fn hash_stable<W: StableHasherResult>(&self,
 247                                           hcx: &mut StableHashingContext<'a>,
 248                                           hasher: &mut StableHasher<W>) {
 249         match hcx.node_id_hashing_mode {
 250             NodeIdHashingMode::Ignore => {
 251                 // Don't do anything.
 252             }
 253             NodeIdHashingMode::HashDefPath => {
 254                 let hir::HirId {
 255                     owner,
 256                     local_id,
 257                 } = *self;
 258
 259                 hcx.local_def_path_hash(owner).hash_stable(hcx, hasher);
 260                 local_id.hash_stable(hcx, hasher);
 261             }
 262         }
 263     }
 264 }
 265
 266 impl<'a> ToStableHashKey<StableHashingContext<'a>> for hir::HirId {
 267     type KeyType = (DefPathHash, hir::ItemLocalId);
 268
 269     #[inline]
 270     fn to_stable_hash_key(&self,
 271                           hcx: &StableHashingContext<'a>)
 272                           -> (DefPathHash, hir::ItemLocalId) {
 273         let def_path_hash = hcx.local_def_path_hash(self.owner);
 274         (def_path_hash, self.local_id)
 275     }
 276 }
 277
 278 impl<'a> HashStable<StableHashingContext<'a>> for ast::NodeId {
 279     fn hash_stable<W: StableHasherResult>(&self,
 280                                           hcx: &mut StableHashingContext<'a>,
 281                                           hasher: &mut StableHasher<W>) {
 282         match hcx.node_id_hashing_mode {
 283             NodeIdHashingMode::Ignore => {
 284                 // Don't do anything.
 285             }
 286             NodeIdHashingMode::HashDefPath => {
 287                 hcx.definitions.node_to_hir_id(*self).hash_stable(hcx, hasher);
 288             }
 289         }
 290     }
 291 }
 292
 293 impl<'a> ToStableHashKey<StableHashingContext<'a>> for ast::NodeId {
 294     type KeyType = (DefPathHash, hir::ItemLocalId);
 295
 296     #[inline]
 297     fn to_stable_hash_key(&self,
 298                           hcx: &StableHashingContext<'a>)
 299                           -> (DefPathHash, hir::ItemLocalId) {
 300         hcx.definitions.node_to_hir_id(*self).to_stable_hash_key(hcx)
 301     }
 302 }
 303
 304 impl<'a> HashStable<StableHashingContext<'a>> for Span {
 305
 306     // Hash a span in a stable way. We can't directly hash the span's BytePos
 307     // fields (that would be similar to hashing pointers, since those are just
 308     // offsets into the SourceMap). Instead, we hash the (file name, line, column)
 309     // triple, which stays the same even if the containing SourceFile has moved
 310     // within the SourceMap.
 311     // Also note that we are hashing byte offsets for the column, not unicode
 312     // codepoint offsets. For the purpose of the hash that's sufficient.
 313     // Also, hashing filenames is expensive so we avoid doing it twice when the
 314     // span starts and ends in the same file, which is almost always the case.
 315     fn hash_stable<W: StableHasherResult>(&self,
 316                                           hcx: &mut StableHashingContext<'a>,
 317                                           hasher: &mut StableHasher<W>) {
 318         const TAG_VALID_SPAN: u8 = 0;
 319         const TAG_INVALID_SPAN: u8 = 1;
 320         const TAG_EXPANSION: u8 = 0;
 321         const TAG_NO_EXPANSION: u8 = 1;
 322
 323         if !hcx.hash_spans {
 324             return
 325         }
 326
 327         if *self == DUMMY_SP {
 328             return std_hash::Hash::hash(&TAG_INVALID_SPAN, hasher);
 329         }
 330
 331         // If this is not an empty or invalid span, we want to hash the last
 332         // position that belongs to it, as opposed to hashing the first
 333         // position past it.
 334         let span = self.data();
 335
 336         if span.hi < span.lo {
 337             return std_hash::Hash::hash(&TAG_INVALID_SPAN, hasher);
 338         }
 339
 340         let (file_lo, line_lo, col_lo) = match hcx.source_map()
 341                                                   .byte_pos_to_line_and_col(span.lo) {
 342             Some(pos) => pos,
 343             None => {
 344                 return std_hash::Hash::hash(&TAG_INVALID_SPAN, hasher);
 345             }
 346         };
 347
 348         if !file_lo.contains(span.hi) {
 349             return std_hash::Hash::hash(&TAG_INVALID_SPAN, hasher);
 350         }
 351
 352         std_hash::Hash::hash(&TAG_VALID_SPAN, hasher);
 353         // We truncate the stable_id hash and line and col numbers. The chances
 354         // of causing a collision this way should be minimal.
 355         std_hash::Hash::hash(&(file_lo.name_hash as u64), hasher);
 356
 357         let col = (col_lo.0 as u64) & 0xFF;
 358         let line = ((line_lo as u64) & 0xFF_FF_FF) << 8;
 359         let len = ((span.hi - span.lo).0 as u64) << 32;
 360         let line_col_len = col | line | len;
 361         std_hash::Hash::hash(&line_col_len, hasher);
 362
 363         if span.ctxt == SyntaxContext::empty() {
 364             TAG_NO_EXPANSION.hash_stable(hcx, hasher);
 365         } else {
 366             TAG_EXPANSION.hash_stable(hcx, hasher);
 367
 368             // Since the same expansion context is usually referenced many
 369             // times, we cache a stable hash of it and hash that instead of
 370             // recursing every time.
 371             thread_local! {
 372                 static CACHE: RefCell<FxHashMap<hygiene::Mark, u64>> = Default::default();
 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 impl<'a> HashStable<StableHashingContext<'a>> for DelimSpan {
 396     fn hash_stable<W: StableHasherResult>(
 397         &self,
 398         hcx: &mut StableHashingContext<'a>,
 399         hasher: &mut StableHasher<W>,
 400     ) {
 401         self.open.hash_stable(hcx, hasher);
 402         self.close.hash_stable(hcx, hasher);
 403     }
 404 }
 405
 406 pub fn hash_stable_trait_impls<'a, 'gcx, W, R>(
 407     hcx: &mut StableHashingContext<'a>,
 408     hasher: &mut StableHasher<W>,
 409     blanket_impls: &[DefId],
 410     non_blanket_impls: &HashMap<fast_reject::SimplifiedType, Vec<DefId>, R>)
 411     where W: StableHasherResult,
 412           R: std_hash::BuildHasher,
 413 {
 414     {
 415         let mut blanket_impls: SmallVec<[_; 8]> = blanket_impls
 416             .iter()
 417             .map(|&def_id| hcx.def_path_hash(def_id))
 418             .collect();
 419
 420         if blanket_impls.len() > 1 {
 421             blanket_impls.sort_unstable();
 422         }
 423
 424         blanket_impls.hash_stable(hcx, hasher);
 425     }
 426
 427     {
 428         let mut keys: SmallVec<[_; 8]> =
 429             non_blanket_impls.keys()
 430                              .map(|k| (k, k.map_def(|d| hcx.def_path_hash(d))))
 431                              .collect();
 432         keys.sort_unstable_by(|&(_, ref k1), &(_, ref k2)| k1.cmp(k2));
 433         keys.len().hash_stable(hcx, hasher);
 434         for (key, ref stable_key) in keys {
 435             stable_key.hash_stable(hcx, hasher);
 436             let mut impls : SmallVec<[_; 8]> = non_blanket_impls[key]
 437                 .iter()
 438                 .map(|&impl_id| hcx.def_path_hash(impl_id))
 439                 .collect();
 440
 441             if impls.len() > 1 {
 442                 impls.sort_unstable();
 443             }
 444
 445             impls.hash_stable(hcx, hasher);
 446         }
 447     }
 448 }
 449