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, CachingCodemapView, Fingerprint};
  16 use middle::cstore::CrateStore;
  17 use ty::{TyCtxt, fast_reject};
  18 use mir::interpret::AllocId;
  19 use session::Session;
  20
  21 use std::cmp::Ord;
  22 use std::hash as std_hash;
  23 use std::collections::HashMap;
  24 use std::cell::RefCell;
  25
  26 use syntax::ast;
  27
  28 use syntax::codemap::CodeMap;
  29 use syntax::ext::hygiene::SyntaxContext;
  30 use syntax::symbol::Symbol;
  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::accumulate_vec::AccumulateVec;
  38 use rustc_data_structures::fx::{FxHashSet, FxHashMap};
  39
  40 pub 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     // CachingCodemapView, so we initialize it lazily.
  61     raw_codemap: &'a CodeMap,
  62     caching_codemap: Option<CachingCodemapView<'a>>,
  63
  64     pub(super) alloc_id_recursion_tracker: FxHashSet<AllocId>,
  65 }
  66
  67 #[derive(PartialEq, Eq, Clone, Copy)]
  68 pub enum NodeIdHashingMode {
  69     Ignore,
  70     HashDefPath,
  71 }
  72
  73 /// The BodyResolver allows to map a BodyId to the corresponding hir::Body.
  74 /// We could also just store a plain reference to the hir::Crate but we want
  75 /// to avoid that the crate is used to get untracked access to all of the HIR.
  76 #[derive(Clone, Copy)]
  77 struct BodyResolver<'gcx>(&'gcx hir::Crate);
  78
  79 impl<'gcx> BodyResolver<'gcx> {
  80     // Return a reference to the hir::Body with the given BodyId.
  81     // DOES NOT DO ANY TRACKING, use carefully.
  82     fn body(self, id: hir::BodyId) -> &'gcx hir::Body {
  83         self.0.body(id)
  84     }
  85 }
  86
  87 impl<'a> StableHashingContext<'a> {
  88     // The `krate` here is only used for mapping BodyIds to Bodies.
  89     // Don't use it for anything else or you'll run the risk of
  90     // leaking data out of the tracking system.
  91     pub fn new(sess: &'a Session,
  92                krate: &'a hir::Crate,
  93                definitions: &'a Definitions,
  94                cstore: &'a dyn CrateStore)
  95                -> Self {
  96         let hash_spans_initial = !sess.opts.debugging_opts.incremental_ignore_spans;
  97
  98         StableHashingContext {
  99             sess,
 100             body_resolver: BodyResolver(krate),
 101             definitions,
 102             cstore,
 103             caching_codemap: None,
 104             raw_codemap: sess.codemap(),
 105             hash_spans: hash_spans_initial,
 106             hash_bodies: true,
 107             node_id_hashing_mode: NodeIdHashingMode::HashDefPath,
 108             alloc_id_recursion_tracker: Default::default(),
 109         }
 110     }
 111
 112     #[inline]
 113     pub fn sess(&self) -> &'a Session {
 114         self.sess
 115     }
 116
 117     #[inline]
 118     pub fn while_hashing_hir_bodies<F: FnOnce(&mut Self)>(&mut self,
 119                                                           hash_bodies: bool,
 120                                                           f: F) {
 121         let prev_hash_bodies = self.hash_bodies;
 122         self.hash_bodies = hash_bodies;
 123         f(self);
 124         self.hash_bodies = prev_hash_bodies;
 125     }
 126
 127     #[inline]
 128     pub fn while_hashing_spans<F: FnOnce(&mut Self)>(&mut self,
 129                                                      hash_spans: bool,
 130                                                      f: F) {
 131         let prev_hash_spans = self.hash_spans;
 132         self.hash_spans = hash_spans;
 133         f(self);
 134         self.hash_spans = prev_hash_spans;
 135     }
 136
 137     #[inline]
 138     pub fn with_node_id_hashing_mode<F: FnOnce(&mut Self)>(&mut self,
 139                                                            mode: NodeIdHashingMode,
 140                                                            f: F) {
 141         let prev = self.node_id_hashing_mode;
 142         self.node_id_hashing_mode = mode;
 143         f(self);
 144         self.node_id_hashing_mode = prev;
 145     }
 146
 147     #[inline]
 148     pub fn def_path_hash(&self, def_id: DefId) -> DefPathHash {
 149         if def_id.is_local() {
 150             self.definitions.def_path_hash(def_id.index)
 151         } else {
 152             self.cstore.def_path_hash(def_id)
 153         }
 154     }
 155
 156     #[inline]
 157     pub fn local_def_path_hash(&self, def_index: DefIndex) -> DefPathHash {
 158         self.definitions.def_path_hash(def_index)
 159     }
 160
 161     #[inline]
 162     pub fn node_to_hir_id(&self, node_id: ast::NodeId) -> hir::HirId {
 163         self.definitions.node_to_hir_id(node_id)
 164     }
 165
 166     #[inline]
 167     pub fn hash_bodies(&self) -> bool {
 168         self.hash_bodies
 169     }
 170
 171     #[inline]
 172     pub fn codemap(&mut self) -> &mut CachingCodemapView<'a> {
 173         match self.caching_codemap {
 174             Some(ref mut cm) => {
 175                 cm
 176             }
 177             ref mut none => {
 178                 *none = Some(CachingCodemapView::new(self.raw_codemap));
 179                 none.as_mut().unwrap()
 180             }
 181         }
 182     }
 183
 184     #[inline]
 185     pub fn is_ignored_attr(&self, name: Symbol) -> bool {
 186         self.sess.ignored_attr_names.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 CodeMap). Instead, we hash the (file name, line, column)
 309     // triple, which stays the same even if the containing FileMap has moved
 310     // within the CodeMap.
 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.codemap()
 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>> =
 373                     RefCell::new(FxHashMap());
 374             }
 375
 376             let sub_hash: u64 = CACHE.with(|cache| {
 377                 let mark = span.ctxt.outer();
 378
 379                 if let Some(&sub_hash) = cache.borrow().get(&mark) {
 380                     return sub_hash;
 381                 }
 382
 383                 let mut hasher = StableHasher::new();
 384                 mark.expn_info().hash_stable(hcx, &mut hasher);
 385                 let sub_hash: Fingerprint = hasher.finish();
 386                 let sub_hash = sub_hash.to_smaller_hash();
 387                 cache.borrow_mut().insert(mark, sub_hash);
 388                 sub_hash
 389             });
 390
 391             sub_hash.hash_stable(hcx, hasher);
 392         }
 393     }
 394 }
 395
 396 pub fn hash_stable_trait_impls<'a, 'gcx, W, R>(
 397     hcx: &mut StableHashingContext<'a>,
 398     hasher: &mut StableHasher<W>,
 399     blanket_impls: &Vec<DefId>,
 400     non_blanket_impls: &HashMap<fast_reject::SimplifiedType, Vec<DefId>, R>)
 401     where W: StableHasherResult,
 402           R: std_hash::BuildHasher,
 403 {
 404     {
 405         let mut blanket_impls: AccumulateVec<[_; 8]> = blanket_impls
 406             .iter()
 407             .map(|&def_id| hcx.def_path_hash(def_id))
 408             .collect();
 409
 410         if blanket_impls.len() > 1 {
 411             blanket_impls.sort_unstable();
 412         }
 413
 414         blanket_impls.hash_stable(hcx, hasher);
 415     }
 416
 417     {
 418         let mut keys: AccumulateVec<[_; 8]> =
 419             non_blanket_impls.keys()
 420                              .map(|k| (k, k.map_def(|d| hcx.def_path_hash(d))))
 421                              .collect();
 422         keys.sort_unstable_by(|&(_, ref k1), &(_, ref k2)| k1.cmp(k2));
 423         keys.len().hash_stable(hcx, hasher);
 424         for (key, ref stable_key) in keys {
 425             stable_key.hash_stable(hcx, hasher);
 426             let mut impls : AccumulateVec<[_; 8]> = non_blanket_impls[key]
 427                 .iter()
 428                 .map(|&impl_id| hcx.def_path_hash(impl_id))
 429                 .collect();
 430
 431             if impls.len() > 1 {
 432                 impls.sort_unstable();
 433             }
 434
 435             impls.hash_stable(hcx, hasher);
 436         }
 437     }
 438 }
 439