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 syntax::ast;
  31 use std::cell::RefCell;
  32 use std::hash::Hash;
  33 use rustc::dep_graph::DepNode;
  34 use rustc::hir;
  35 use rustc::hir::def_id::{CRATE_DEF_INDEX, DefId};
  36 use rustc::hir::intravisit as visit;
  37 use rustc::ty::TyCtxt;
  38 use rustc_data_structures::fnv::FnvHashMap;
  39 use rustc::util::common::record_time;
  40 use rustc::session::config::DebugInfoLevel::NoDebugInfo;
  41
  42 use self::def_path_hash::DefPathHashes;
  43 use self::svh_visitor::StrictVersionHashVisitor;
  44 use self::caching_codemap_view::CachingCodemapView;
  45 use self::hasher::IchHasher;
  46 use ich::Fingerprint;
  47
  48 mod def_path_hash;
  49 mod svh_visitor;
  50 mod caching_codemap_view;
  51 pub mod hasher;
  52
  53 pub struct IncrementalHashesMap {
  54     hashes: FnvHashMap<DepNode<DefId>, Fingerprint>,
  55
  56     // These are the metadata hashes for the current crate as they were stored
  57     // during the last compilation session. They are only loaded if
  58     // -Z query-dep-graph was specified and are needed for auto-tests using
  59     // the #[rustc_metadata_dirty] and #[rustc_metadata_clean] attributes to
  60     // check whether some metadata hash has changed in between two revisions.
  61     pub prev_metadata_hashes: RefCell<FnvHashMap<DefId, Fingerprint>>,
  62 }
  63
  64 impl IncrementalHashesMap {
  65     pub fn new() -> IncrementalHashesMap {
  66         IncrementalHashesMap {
  67             hashes: FnvHashMap(),
  68             prev_metadata_hashes: RefCell::new(FnvHashMap()),
  69         }
  70     }
  71
  72     pub fn insert(&mut self, k: DepNode<DefId>, v: Fingerprint) -> Option<Fingerprint> {
  73         self.hashes.insert(k, v)
  74     }
  75
  76     pub fn iter<'a>(&'a self)
  77                     -> ::std::collections::hash_map::Iter<'a, DepNode<DefId>, Fingerprint> {
  78         self.hashes.iter()
  79     }
  80
  81     pub fn len(&self) -> usize {
  82         self.hashes.len()
  83     }
  84 }
  85
  86 impl<'a> ::std::ops::Index<&'a DepNode<DefId>> for IncrementalHashesMap {
  87     type Output = Fingerprint;
  88
  89     fn index(&self, index: &'a DepNode<DefId>) -> &Fingerprint {
  90         &self.hashes[index]
  91     }
  92 }
  93
  94
  95 pub fn compute_incremental_hashes_map<'a, 'tcx: 'a>(tcx: TyCtxt<'a, 'tcx, 'tcx>)
  96                                                     -> IncrementalHashesMap {
  97     let _ignore = tcx.dep_graph.in_ignore();
  98     let krate = tcx.map.krate();
  99     let hash_spans = tcx.sess.opts.debuginfo != NoDebugInfo;
 100     let mut visitor = HashItemsVisitor {
 101         tcx: tcx,
 102         hashes: IncrementalHashesMap::new(),
 103         def_path_hashes: DefPathHashes::new(tcx),
 104         codemap: CachingCodemapView::new(tcx),
 105         hash_spans: hash_spans,
 106     };
 107     record_time(&tcx.sess.perf_stats.incr_comp_hashes_time, || {
 108         visitor.calculate_def_id(DefId::local(CRATE_DEF_INDEX),
 109                                  |v| visit::walk_crate(v, krate));
 110         krate.visit_all_items(&mut visitor);
 111     });
 112
 113     tcx.sess.perf_stats.incr_comp_hashes_count.set(visitor.hashes.len() as u64);
 114
 115     record_time(&tcx.sess.perf_stats.svh_time, || visitor.compute_crate_hash());
 116     visitor.hashes
 117 }
 118
 119 struct HashItemsVisitor<'a, 'tcx: 'a> {
 120     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 121     def_path_hashes: DefPathHashes<'a, 'tcx>,
 122     codemap: CachingCodemapView<'tcx>,
 123     hashes: IncrementalHashesMap,
 124     hash_spans: bool,
 125 }
 126
 127 impl<'a, 'tcx> HashItemsVisitor<'a, 'tcx> {
 128     fn calculate_node_id<W>(&mut self, id: ast::NodeId, walk_op: W)
 129         where W: for<'v> FnMut(&mut StrictVersionHashVisitor<'v, 'a, 'tcx>)
 130     {
 131         let def_id = self.tcx.map.local_def_id(id);
 132         self.calculate_def_id(def_id, walk_op)
 133     }
 134
 135     fn calculate_def_id<W>(&mut self, def_id: DefId, mut walk_op: W)
 136         where W: for<'v> FnMut(&mut StrictVersionHashVisitor<'v, 'a, 'tcx>)
 137     {
 138         assert!(def_id.is_local());
 139         debug!("HashItemsVisitor::calculate(def_id={:?})", def_id);
 140         let mut state = IchHasher::new();
 141         walk_op(&mut StrictVersionHashVisitor::new(&mut state,
 142                                                    self.tcx,
 143                                                    &mut self.def_path_hashes,
 144                                                    &mut self.codemap,
 145                                                    self.hash_spans));
 146         let bytes_hashed = state.bytes_hashed();
 147         let item_hash = state.finish();
 148         self.hashes.insert(DepNode::Hir(def_id), item_hash);
 149         debug!("calculate_item_hash: def_id={:?} hash={:?}", def_id, item_hash);
 150
 151         let bytes_hashed = self.tcx.sess.perf_stats.incr_comp_bytes_hashed.get() +
 152                            bytes_hashed;
 153         self.tcx.sess.perf_stats.incr_comp_bytes_hashed.set(bytes_hashed);
 154     }
 155
 156     fn compute_crate_hash(&mut self) {
 157         let krate = self.tcx.map.krate();
 158
 159         let mut crate_state = IchHasher::new();
 160
 161         let crate_disambiguator = self.tcx.sess.local_crate_disambiguator();
 162         "crate_disambiguator".hash(&mut crate_state);
 163         crate_disambiguator.len().hash(&mut crate_state);
 164         crate_disambiguator.hash(&mut crate_state);
 165
 166         // add each item (in some deterministic order) to the overall
 167         // crate hash.
 168         {
 169             let def_path_hashes = &mut self.def_path_hashes;
 170             let mut item_hashes: Vec<_> =
 171                 self.hashes.iter()
 172                            .map(|(item_dep_node, &item_hash)| {
 173                                // convert from a DepNode<DefId> tp a
 174                                // DepNode<u64> where the u64 is the
 175                                // hash of the def-id's def-path:
 176                                let item_dep_node =
 177                                    item_dep_node.map_def(|&did| Some(def_path_hashes.hash(did)))
 178                                                 .unwrap();
 179                                (item_dep_node, item_hash)
 180                            })
 181                            .collect();
 182             item_hashes.sort(); // avoid artificial dependencies on item ordering
 183             item_hashes.hash(&mut crate_state);
 184         }
 185
 186         {
 187             let mut visitor = StrictVersionHashVisitor::new(&mut crate_state,
 188                                                             self.tcx,
 189                                                             &mut self.def_path_hashes,
 190                                                             &mut self.codemap,
 191                                                             self.hash_spans);
 192             visitor.hash_attributes(&krate.attrs);
 193         }
 194
 195         let crate_hash = crate_state.finish();
 196         self.hashes.insert(DepNode::Krate, crate_hash);
 197         debug!("calculate_crate_hash: crate_hash={:?}", crate_hash);
 198     }
 199 }
 200
 201
 202 impl<'a, 'tcx> visit::Visitor<'tcx> for HashItemsVisitor<'a, 'tcx> {
 203     fn visit_item(&mut self, item: &'tcx hir::Item) {
 204         self.calculate_node_id(item.id, |v| v.visit_item(item));
 205         visit::walk_item(self, item);
 206     }
 207
 208     fn visit_foreign_item(&mut self, item: &'tcx hir::ForeignItem) {
 209         self.calculate_node_id(item.id, |v| v.visit_foreign_item(item));
 210         visit::walk_foreign_item(self, item);
 211     }
 212 }
 213