src/librustc/dep_graph/graph.rs

   1 // Copyright 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 use hir::def_id::DefId;
  12 use rustc_data_structures::fx::FxHashMap;
  13 use session::config::OutputType;
  14 use std::cell::{Ref, RefCell};
  15 use std::rc::Rc;
  16 use std::sync::Arc;
  17
  18 use super::dep_node::{DepNode, WorkProductId};
  19 use super::query::DepGraphQuery;
  20 use super::raii;
  21 use super::safe::DepGraphSafe;
  22 use super::thread::{DepGraphThreadData, DepMessage};
  23
  24 #[derive(Clone)]
  25 pub struct DepGraph {
  26     data: Rc<DepGraphData>
  27 }
  28
  29 struct DepGraphData {
  30     /// We send messages to the thread to let it build up the dep-graph
  31     /// from the current run.
  32     thread: DepGraphThreadData,
  33
  34     /// When we load, there may be `.o` files, cached mir, or other such
  35     /// things available to us. If we find that they are not dirty, we
  36     /// load the path to the file storing those work-products here into
  37     /// this map. We can later look for and extract that data.
  38     previous_work_products: RefCell<FxHashMap<Arc<WorkProductId>, WorkProduct>>,
  39
  40     /// Work-products that we generate in this run.
  41     work_products: RefCell<FxHashMap<Arc<WorkProductId>, WorkProduct>>,
  42 }
  43
  44 impl DepGraph {
  45     pub fn new(enabled: bool) -> DepGraph {
  46         DepGraph {
  47             data: Rc::new(DepGraphData {
  48                 thread: DepGraphThreadData::new(enabled),
  49                 previous_work_products: RefCell::new(FxHashMap()),
  50                 work_products: RefCell::new(FxHashMap()),
  51             })
  52         }
  53     }
  54
  55     /// True if we are actually building the full dep-graph.
  56     #[inline]
  57     pub fn is_fully_enabled(&self) -> bool {
  58         self.data.thread.is_fully_enabled()
  59     }
  60
  61     pub fn query(&self) -> DepGraphQuery<DefId> {
  62         self.data.thread.query()
  63     }
  64
  65     pub fn in_ignore<'graph>(&'graph self) -> Option<raii::IgnoreTask<'graph>> {
  66         raii::IgnoreTask::new(&self.data.thread)
  67     }
  68
  69     pub fn in_task<'graph>(&'graph self, key: DepNode<DefId>) -> Option<raii::DepTask<'graph>> {
  70         raii::DepTask::new(&self.data.thread, key)
  71     }
  72
  73     pub fn with_ignore<OP,R>(&self, op: OP) -> R
  74         where OP: FnOnce() -> R
  75     {
  76         let _task = self.in_ignore();
  77         op()
  78     }
  79
  80     /// Starts a new dep-graph task. Dep-graph tasks are specified
  81     /// using a free function (`task`) and **not** a closure -- this
  82     /// is intentional because we want to exercise tight control over
  83     /// what state they have access to. In particular, we want to
  84     /// prevent implicit 'leaks' of tracked state into the task (which
  85     /// could then be read without generating correct edges in the
  86     /// dep-graph -- see the [README] for more details on the
  87     /// dep-graph). To this end, the task function gets exactly two
  88     /// pieces of state: the context `cx` and an argument `arg`. Both
  89     /// of these bits of state must be of some type that implements
  90     /// `DepGraphSafe` and hence does not leak.
  91     ///
  92     /// The choice of two arguments is not fundamental. One argument
  93     /// would work just as well, since multiple values can be
  94     /// collected using tuples. However, using two arguments works out
  95     /// to be quite convenient, since it is common to need a context
  96     /// (`cx`) and some argument (e.g., a `DefId` identifying what
  97     /// item to process).
  98     ///
  99     /// For cases where you need some other number of arguments:
 100     ///
 101     /// - If you only need one argument, just use `()` for the `arg`
 102     ///   parameter.
 103     /// - If you need 3+ arguments, use a tuple for the
 104     ///   `arg` parameter.
 105     ///
 106     /// [README]: README.md
 107     pub fn with_task<C, A, R>(&self, key: DepNode<DefId>, cx: C, arg: A, task: fn(C, A) -> R) -> R
 108         where C: DepGraphSafe, A: DepGraphSafe
 109     {
 110         let _task = self.in_task(key);
 111         task(cx, arg)
 112     }
 113
 114     pub fn read(&self, v: DepNode<DefId>) {
 115         if self.data.thread.is_enqueue_enabled() {
 116             self.data.thread.enqueue(DepMessage::Read(v));
 117         }
 118     }
 119
 120     pub fn write(&self, v: DepNode<DefId>) {
 121         if self.data.thread.is_enqueue_enabled() {
 122             self.data.thread.enqueue(DepMessage::Write(v));
 123         }
 124     }
 125
 126     /// Indicates that a previous work product exists for `v`. This is
 127     /// invoked during initial start-up based on what nodes are clean
 128     /// (and what files exist in the incr. directory).
 129     pub fn insert_previous_work_product(&self, v: &Arc<WorkProductId>, data: WorkProduct) {
 130         debug!("insert_previous_work_product({:?}, {:?})", v, data);
 131         self.data.previous_work_products.borrow_mut()
 132                                         .insert(v.clone(), data);
 133     }
 134
 135     /// Indicates that we created the given work-product in this run
 136     /// for `v`. This record will be preserved and loaded in the next
 137     /// run.
 138     pub fn insert_work_product(&self, v: &Arc<WorkProductId>, data: WorkProduct) {
 139         debug!("insert_work_product({:?}, {:?})", v, data);
 140         self.data.work_products.borrow_mut()
 141                                .insert(v.clone(), data);
 142     }
 143
 144     /// Check whether a previous work product exists for `v` and, if
 145     /// so, return the path that leads to it. Used to skip doing work.
 146     pub fn previous_work_product(&self, v: &Arc<WorkProductId>) -> Option<WorkProduct> {
 147         self.data.previous_work_products.borrow()
 148                                         .get(v)
 149                                         .cloned()
 150     }
 151
 152     /// Access the map of work-products created during this run. Only
 153     /// used during saving of the dep-graph.
 154     pub fn work_products(&self) -> Ref<FxHashMap<Arc<WorkProductId>, WorkProduct>> {
 155         self.data.work_products.borrow()
 156     }
 157
 158     /// Access the map of work-products created during the cached run. Only
 159     /// used during saving of the dep-graph.
 160     pub fn previous_work_products(&self) -> Ref<FxHashMap<Arc<WorkProductId>, WorkProduct>> {
 161         self.data.previous_work_products.borrow()
 162     }
 163 }
 164
 165 /// A "work product" is an intermediate result that we save into the
 166 /// incremental directory for later re-use. The primary example are
 167 /// the object files that we save for each partition at code
 168 /// generation time.
 169 ///
 170 /// Each work product is associated with a dep-node, representing the
 171 /// process that produced the work-product. If that dep-node is found
 172 /// to be dirty when we load up, then we will delete the work-product
 173 /// at load time. If the work-product is found to be clean, then we
 174 /// will keep a record in the `previous_work_products` list.
 175 ///
 176 /// In addition, work products have an associated hash. This hash is
 177 /// an extra hash that can be used to decide if the work-product from
 178 /// a previous compilation can be re-used (in addition to the dirty
 179 /// edges check).
 180 ///
 181 /// As the primary example, consider the object files we generate for
 182 /// each partition. In the first run, we create partitions based on
 183 /// the symbols that need to be compiled. For each partition P, we
 184 /// hash the symbols in P and create a `WorkProduct` record associated
 185 /// with `DepNode::TransPartition(P)`; the hash is the set of symbols
 186 /// in P.
 187 ///
 188 /// The next time we compile, if the `DepNode::TransPartition(P)` is
 189 /// judged to be clean (which means none of the things we read to
 190 /// generate the partition were found to be dirty), it will be loaded
 191 /// into previous work products. We will then regenerate the set of
 192 /// symbols in the partition P and hash them (note that new symbols
 193 /// may be added -- for example, new monomorphizations -- even if
 194 /// nothing in P changed!). We will compare that hash against the
 195 /// previous hash. If it matches up, we can reuse the object file.
 196 #[derive(Clone, Debug, RustcEncodable, RustcDecodable)]
 197 pub struct WorkProduct {
 198     /// Extra hash used to decide if work-product is still suitable;
 199     /// note that this is *not* a hash of the work-product itself.
 200     /// See documentation on `WorkProduct` type for an example.
 201     pub input_hash: u64,
 202
 203     /// Saved files associated with this CGU
 204     pub saved_files: Vec<(OutputType, String)>,
 205 }