src/librustc_incremental/calculate_svh/mod.rs

   1 // Copyright 2012-2014 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 //! Calculation of the (misnamed) "strict version hash" for crates and
  12 //! items. This hash is used to tell when the HIR changed in such a
  13 //! way that results from previous compilations may no longer be
  14 //! applicable and hence must be recomputed. It should probably be
  15 //! renamed to the ICH (incremental compilation hash).
  16 //!
  17 //! The hashes for all items are computed once at the beginning of
  18 //! compilation and stored into a map. In addition, a hash is computed
  19 //! of the **entire crate**.
  20 //!
  21 //! Storing the hashes in a map avoids the need to compute them twice
  22 //! (once when loading prior incremental results and once when
  23 //! saving), but it is also important for correctness: at least as of
  24 //! the time of this writing, the typeck passes rewrites entries in
  25 //! the dep-map in-place to accommodate UFCS resolutions. Since name
  26 //! resolution is part of the hash, the result is that hashes computed
  27 //! at the end of compilation would be different from those computed
  28 //! at the beginning.
  29
  30 use std::cell::RefCell;
  31 use std::hash::Hash;
  32 use std::sync::Arc;
  33 use rustc::dep_graph::DepNode;
  34 use rustc::hir;
  35 use rustc::hir::def_id::{LOCAL_CRATE, CRATE_DEF_INDEX, DefId};
  36 use rustc::hir::itemlikevisit::ItemLikeVisitor;
  37 use rustc::ich::{Fingerprint, StableHashingContext};
  38 use rustc::ty::TyCtxt;
  39 use rustc_data_structures::stable_hasher::{StableHasher, HashStable};
  40 use rustc_data_structures::fx::FxHashMap;
  41 use rustc::util::common::record_time;
  42
  43 pub type IchHasher = StableHasher<Fingerprint>;
  44
  45 pub struct IncrementalHashesMap {
  46     hashes: FxHashMap<DepNode<DefId>, Fingerprint>,
  47
  48     // These are the metadata hashes for the current crate as they were stored
  49     // during the last compilation session. They are only loaded if
  50     // -Z query-dep-graph was specified and are needed for auto-tests using
  51     // the #[rustc_metadata_dirty] and #[rustc_metadata_clean] attributes to
  52     // check whether some metadata hash has changed in between two revisions.
  53     pub prev_metadata_hashes: RefCell<FxHashMap<DefId, Fingerprint>>,
  54 }
  55
  56 impl IncrementalHashesMap {
  57     pub fn new() -> IncrementalHashesMap {
  58         IncrementalHashesMap {
  59             hashes: FxHashMap(),
  60             prev_metadata_hashes: RefCell::new(FxHashMap()),
  61         }
  62     }
  63
  64     pub fn get(&self, k: &DepNode<DefId>) -> Option<&Fingerprint> {
  65         self.hashes.get(k)
  66     }
  67
  68     pub fn insert(&mut self, k: DepNode<DefId>, v: Fingerprint) -> Option<Fingerprint> {
  69         self.hashes.insert(k, v)
  70     }
  71
  72     pub fn iter<'a>(&'a self)
  73                     -> ::std::collections::hash_map::Iter<'a, DepNode<DefId>, Fingerprint> {
  74         self.hashes.iter()
  75     }
  76
  77     pub fn len(&self) -> usize {
  78         self.hashes.len()
  79     }
  80 }
  81
  82 impl<'a> ::std::ops::Index<&'a DepNode<DefId>> for IncrementalHashesMap {
  83     type Output = Fingerprint;
  84
  85     fn index(&self, index: &'a DepNode<DefId>) -> &Fingerprint {
  86         match self.hashes.get(index) {
  87             Some(fingerprint) => fingerprint,
  88             None => {
  89                 bug!("Could not find ICH for {:?}", index);
  90             }
  91         }
  92     }
  93 }
  94
  95 struct ComputeItemHashesVisitor<'a, 'tcx: 'a> {
  96     hcx: StableHashingContext<'a, 'tcx>,
  97     hashes: IncrementalHashesMap,
  98 }
  99
 100 impl<'a, 'tcx: 'a> ComputeItemHashesVisitor<'a, 'tcx> {
 101     fn compute_and_store_ich_for_item_like<T>(&mut self,
 102                                               dep_node: DepNode<DefId>,
 103                                               hash_bodies: bool,
 104                                               item_like: T)
 105         where T: HashStable<StableHashingContext<'a, 'tcx>>
 106     {
 107         if !hash_bodies && !self.hcx.tcx().sess.opts.build_dep_graph() {
 108             // If we just need the hashes in order to compute the SVH, we don't
 109             // need have two hashes per item. Just the one containing also the
 110             // item's body is sufficient.
 111             return
 112         }
 113
 114         let mut hasher = IchHasher::new();
 115         self.hcx.while_hashing_hir_bodies(hash_bodies, |hcx| {
 116             item_like.hash_stable(hcx, &mut hasher);
 117         });
 118
 119         let bytes_hashed = hasher.bytes_hashed();
 120         let item_hash = hasher.finish();
 121         debug!("calculate_def_hash: dep_node={:?} hash={:?}", dep_node, item_hash);
 122         self.hashes.insert(dep_node, item_hash);
 123
 124         let tcx = self.hcx.tcx();
 125         let bytes_hashed =
 126             tcx.sess.perf_stats.incr_comp_bytes_hashed.get() +
 127             bytes_hashed;
 128         tcx.sess.perf_stats.incr_comp_bytes_hashed.set(bytes_hashed);
 129     }
 130
 131     fn compute_crate_hash(&mut self) {
 132         let tcx = self.hcx.tcx();
 133         let krate = tcx.hir.krate();
 134
 135         let mut crate_state = IchHasher::new();
 136
 137         let crate_disambiguator = tcx.sess.local_crate_disambiguator();
 138         "crate_disambiguator".hash(&mut crate_state);
 139         crate_disambiguator.as_str().len().hash(&mut crate_state);
 140         crate_disambiguator.as_str().hash(&mut crate_state);
 141
 142         // add each item (in some deterministic order) to the overall
 143         // crate hash.
 144         {
 145             let hcx = &mut self.hcx;
 146             let mut item_hashes: Vec<_> =
 147                 self.hashes.iter()
 148                            .filter_map(|(item_dep_node, &item_hash)| {
 149                                 // This `match` determines what kinds of nodes
 150                                 // go into the SVH:
 151                                 match *item_dep_node {
 152                                     DepNode::Hir(_) |
 153                                     DepNode::HirBody(_) => {
 154                                         // We want to incoporate these into the
 155                                         // SVH.
 156                                     }
 157                                     DepNode::FileMap(..) => {
 158                                         // These don't make a semantic
 159                                         // difference, filter them out.
 160                                         return None
 161                                     }
 162                                     ref other => {
 163                                         bug!("Found unexpected DepNode during \
 164                                               SVH computation: {:?}",
 165                                              other)
 166                                     }
 167                                 }
 168
 169                                 // Convert from a DepNode<DefId> to a
 170                                 // DepNode<u64> where the u64 is the hash of
 171                                 // the def-id's def-path:
 172                                 let item_dep_node =
 173                                     item_dep_node.map_def(|&did| Some(hcx.def_path_hash(did)))
 174                                                  .unwrap();
 175                                 Some((item_dep_node, item_hash))
 176                            })
 177                            .collect();
 178             item_hashes.sort_unstable(); // avoid artificial dependencies on item ordering
 179             item_hashes.hash(&mut crate_state);
 180         }
 181
 182         krate.attrs.hash_stable(&mut self.hcx, &mut crate_state);
 183
 184         let crate_hash = crate_state.finish();
 185         self.hashes.insert(DepNode::Krate, crate_hash);
 186         debug!("calculate_crate_hash: crate_hash={:?}", crate_hash);
 187     }
 188
 189     fn hash_crate_root_module(&mut self, krate: &'tcx hir::Crate) {
 190         let hir::Crate {
 191             ref module,
 192             // Crate attributes are not copied over to the root `Mod`, so hash
 193             // them explicitly here.
 194             ref attrs,
 195             span,
 196
 197             // These fields are handled separately:
 198             exported_macros: _,
 199             items: _,
 200             trait_items: _,
 201             impl_items: _,
 202             bodies: _,
 203             trait_impls: _,
 204             trait_default_impl: _,
 205             body_ids: _,
 206         } = *krate;
 207
 208         let def_id = DefId::local(CRATE_DEF_INDEX);
 209         self.compute_and_store_ich_for_item_like(DepNode::Hir(def_id),
 210                                                  false,
 211                                                  (module, (span, attrs)));
 212         self.compute_and_store_ich_for_item_like(DepNode::HirBody(def_id),
 213                                                  true,
 214                                                  (module, (span, attrs)));
 215     }
 216 }
 217
 218 impl<'a, 'tcx: 'a> ItemLikeVisitor<'tcx> for ComputeItemHashesVisitor<'a, 'tcx> {
 219     fn visit_item(&mut self, item: &'tcx hir::Item) {
 220         let def_id = self.hcx.tcx().hir.local_def_id(item.id);
 221         self.compute_and_store_ich_for_item_like(DepNode::Hir(def_id), false, item);
 222         self.compute_and_store_ich_for_item_like(DepNode::HirBody(def_id), true, item);
 223     }
 224
 225     fn visit_trait_item(&mut self, item: &'tcx hir::TraitItem) {
 226         let def_id = self.hcx.tcx().hir.local_def_id(item.id);
 227         self.compute_and_store_ich_for_item_like(DepNode::Hir(def_id), false, item);
 228         self.compute_and_store_ich_for_item_like(DepNode::HirBody(def_id), true, item);
 229     }
 230
 231     fn visit_impl_item(&mut self, item: &'tcx hir::ImplItem) {
 232         let def_id = self.hcx.tcx().hir.local_def_id(item.id);
 233         self.compute_and_store_ich_for_item_like(DepNode::Hir(def_id), false, item);
 234         self.compute_and_store_ich_for_item_like(DepNode::HirBody(def_id), true, item);
 235     }
 236 }
 237
 238 pub fn compute_incremental_hashes_map<'a, 'tcx: 'a>(tcx: TyCtxt<'a, 'tcx, 'tcx>)
 239                                                     -> IncrementalHashesMap {
 240     let _ignore = tcx.dep_graph.in_ignore();
 241     let krate = tcx.hir.krate();
 242
 243     let mut visitor = ComputeItemHashesVisitor {
 244         hcx: StableHashingContext::new(tcx),
 245         hashes: IncrementalHashesMap::new(),
 246     };
 247
 248     record_time(&tcx.sess.perf_stats.incr_comp_hashes_time, || {
 249         visitor.hash_crate_root_module(krate);
 250         krate.visit_all_item_likes(&mut visitor);
 251
 252         for macro_def in krate.exported_macros.iter() {
 253             let def_id = tcx.hir.local_def_id(macro_def.id);
 254             visitor.compute_and_store_ich_for_item_like(DepNode::Hir(def_id), false, macro_def);
 255             visitor.compute_and_store_ich_for_item_like(DepNode::HirBody(def_id), true, macro_def);
 256         }
 257
 258         for filemap in tcx.sess
 259                           .codemap()
 260                           .files_untracked()
 261                           .iter()
 262                           .filter(|fm| !fm.is_imported()) {
 263             assert_eq!(LOCAL_CRATE.as_u32(), filemap.crate_of_origin);
 264             let def_id = DefId {
 265                 krate: LOCAL_CRATE,
 266                 index: CRATE_DEF_INDEX,
 267             };
 268             let name = Arc::new(filemap.name.clone());
 269             let dep_node = DepNode::FileMap(def_id, name);
 270             let mut hasher = IchHasher::new();
 271             filemap.hash_stable(&mut visitor.hcx, &mut hasher);
 272             let fingerprint = hasher.finish();
 273             visitor.hashes.insert(dep_node, fingerprint);
 274         }
 275     });
 276
 277     tcx.sess.perf_stats.incr_comp_hashes_count.set(visitor.hashes.len() as u64);
 278
 279     record_time(&tcx.sess.perf_stats.svh_time, || visitor.compute_crate_hash());
 280     visitor.hashes
 281 }