1 // Copyright 2012-2015 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.
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.
11 //! Builder types for generating the "item data" section of the
12 //! metadata. This section winds up looking like this:
15 //! <common::data> // big list of item-like things...
16 //! <common::data_item> // ...for most def-ids, there is an entry.
17 //! </common::data_item>
21 //! As we generate this listing, we collect the offset of each
22 //! `data_item` entry and store it in an index. Then, when we load the
23 //! metadata, we can skip right to the metadata for a particular item.
25 //! In addition to the offset, we need to track the data that was used
26 //! to generate the contents of each `data_item`. This is so that we
27 //! can figure out which HIR nodes contributed to that data for
28 //! incremental compilation purposes.
30 //! The `IndexBuilder` facilitates both of these. It is created
31 //! with an `EncodingContext` (`ecx`), which it encapsulates.
32 //! It has one main method, `record()`. You invoke `record`
33 //! like so to create a new `data_item` element in the list:
36 //! index.record(some_def_id, callback_fn, data)
39 //! What record will do is to (a) record the current offset, (b) emit
40 //! the `common::data_item` tag, and then call `callback_fn` with the
41 //! given data as well as the `EncodingContext`. Once `callback_fn`
42 //! returns, the `common::data_item` tag will be closed.
44 //! `EncodingContext` does not offer the `record` method, so that we
45 //! can ensure that `common::data_item` elements are never nested.
47 //! In addition, while the `callback_fn` is executing, we will push a
48 //! task `MetaData(some_def_id)`, which can then observe the
49 //! reads/writes that occur in the task. For this reason, the `data`
50 //! argument that is given to the `callback_fn` must implement the
51 //! trait `DepGraphRead`, which indicates how to register reads on the
52 //! data in this new task (note that many types of data, such as
53 //! `DefId`, do not currently require any reads to be registered,
54 //! since they are not derived from a HIR node). This is also why we
55 //! give a callback fn, rather than taking a closure: it allows us to
56 //! easily control precisely what data is given to that fn.
58 use encoder::EncodeContext;
63 use rustc::hir::def_id::DefId;
64 use rustc::ich::{StableHashingContext, Fingerprint};
65 use rustc::middle::cstore::EncodedMetadataHash;
66 use rustc::ty::TyCtxt;
69 use std::ops::{Deref, DerefMut};
71 use rustc_data_structures::accumulate_vec::AccumulateVec;
72 use rustc_data_structures::stable_hasher::{StableHasher, HashStable};
73 use rustc_serialize::Encodable;
75 /// Builder that can encode new items, adding them into the index.
76 /// Item encoding cannot be nested.
77 pub struct IndexBuilder<'a, 'b: 'a, 'tcx: 'b> {
79 pub ecx: &'a mut EncodeContext<'b, 'tcx>,
82 impl<'a, 'b, 'tcx> Deref for IndexBuilder<'a, 'b, 'tcx> {
83 type Target = EncodeContext<'b, 'tcx>;
84 fn deref(&self) -> &Self::Target {
89 impl<'a, 'b, 'tcx> DerefMut for IndexBuilder<'a, 'b, 'tcx> {
90 fn deref_mut(&mut self) -> &mut Self::Target {
95 impl<'a, 'b, 'tcx> IndexBuilder<'a, 'b, 'tcx> {
96 pub fn new(ecx: &'a mut EncodeContext<'b, 'tcx>) -> Self {
98 items: Index::new(ecx.tcx.hir.definitions().def_index_counts_lo_hi()),
103 /// Emit the data for a def-id to the metadata. The function to
104 /// emit the data is `op`, and it will be given `data` as
105 /// arguments. This `record` function will call `op` to generate
106 /// the `Entry` (which may point to other encoded information)
107 /// and will then record the `Lazy<Entry>` for use in the index.
109 /// In addition, it will setup a dep-graph task to track what data
110 /// `op` accesses to generate the metadata, which is later used by
111 /// incremental compilation to compute a hash for the metadata and
114 /// The reason that `op` is a function pointer, and not a closure,
115 /// is that we want to be able to completely track all data it has
116 /// access to, so that we can be sure that `DATA: DepGraphRead`
117 /// holds, and that it is therefore not gaining "secret" access to
118 /// bits of HIR or other state that would not be trackd by the
120 pub fn record<'x, DATA>(&'x mut self,
122 op: fn(&mut EntryBuilder<'x, 'b, 'tcx>, DATA) -> Entry<'tcx>,
124 where DATA: DepGraphRead
126 assert!(id.is_local());
127 let tcx: TyCtxt<'b, 'tcx, 'tcx> = self.ecx.tcx;
129 // We don't track this since we are explicitly computing the incr. comp.
130 // hashes anyway. In theory we could do some tracking here and use it to
131 // avoid rehashing things (and instead cache the hashes) but it's
132 // unclear whether that would be a win since hashing is cheap enough.
133 let _task = tcx.dep_graph.in_ignore();
135 let compute_ich = (tcx.sess.opts.debugging_opts.query_dep_graph ||
136 tcx.sess.opts.debugging_opts.incremental_cc) &&
137 tcx.sess.opts.build_dep_graph();
139 let ecx: &'x mut EncodeContext<'b, 'tcx> = &mut *self.ecx;
140 let mut entry_builder = EntryBuilder {
143 hcx: if compute_ich {
144 Some((StableHashingContext::new(tcx), StableHasher::new()))
150 let entry = op(&mut entry_builder, data);
152 if let Some((ref mut hcx, ref mut hasher)) = entry_builder.hcx {
153 entry.hash_stable(hcx, hasher);
156 let entry = entry_builder.ecx.lazy(&entry);
157 entry_builder.finish(id);
158 self.items.record(id, entry);
161 pub fn into_items(self) -> Index {
166 /// Trait used for data that can be passed from outside a dep-graph
167 /// task. The data must either be of some safe type, such as a
168 /// `DefId` index, or implement the `read` method so that it can add
169 /// a read of whatever dep-graph nodes are appropriate.
170 pub trait DepGraphRead {
171 fn read(&self, tcx: TyCtxt);
174 impl DepGraphRead for DefId {
175 fn read(&self, _tcx: TyCtxt) {}
178 impl DepGraphRead for ast::NodeId {
179 fn read(&self, _tcx: TyCtxt) {}
182 impl<T> DepGraphRead for Option<T>
183 where T: DepGraphRead
185 fn read(&self, tcx: TyCtxt) {
187 Some(ref v) => v.read(tcx),
193 impl<T> DepGraphRead for [T]
194 where T: DepGraphRead
196 fn read(&self, tcx: TyCtxt) {
203 macro_rules! read_tuple {
204 ($($name:ident),*) => {
205 impl<$($name),*> DepGraphRead for ($($name),*)
206 where $($name: DepGraphRead),*
208 #[allow(non_snake_case)]
209 fn read(&self, tcx: TyCtxt) {
210 let &($(ref $name),*) = self;
217 read_tuple!(A, B, C);
219 macro_rules! read_hir {
221 impl<'tcx> DepGraphRead for &'tcx $t {
222 fn read(&self, tcx: TyCtxt) {
223 tcx.hir.read(self.id);
228 read_hir!(hir::Item);
229 read_hir!(hir::ImplItem);
230 read_hir!(hir::TraitItem);
231 read_hir!(hir::ForeignItem);
232 read_hir!(hir::MacroDef);
234 /// Leaks access to a value of type T without any tracking. This is
235 /// suitable for ambiguous types like `usize`, which *could* represent
236 /// tracked data (e.g., if you read it out of a HIR node) or might not
237 /// (e.g., if it's an index). Adding in an `Untracked` is an
238 /// assertion, essentially, that the data does not need to be tracked
239 /// (or that read edges will be added by some other way).
241 /// A good idea is to add to each use of `Untracked` an explanation of
242 /// why this value is ok.
243 pub struct Untracked<T>(pub T);
245 impl<T> DepGraphRead for Untracked<T> {
246 fn read(&self, _tcx: TyCtxt) {}
249 /// Newtype that can be used to package up misc data extracted from a
250 /// HIR node that doesn't carry its own id. This will allow an
251 /// arbitrary `T` to be passed in, but register a read on the given
253 pub struct FromId<T>(pub ast::NodeId, pub T);
255 impl<T> DepGraphRead for FromId<T> {
256 fn read(&self, tcx: TyCtxt) {
257 tcx.hir.read(self.0);
261 pub struct EntryBuilder<'a, 'b: 'a, 'tcx: 'b> {
262 pub tcx: TyCtxt<'b, 'tcx, 'tcx>,
263 ecx: &'a mut EncodeContext<'b, 'tcx>,
264 hcx: Option<(StableHashingContext<'b, 'tcx>, StableHasher<Fingerprint>)>,
267 impl<'a, 'b: 'a, 'tcx: 'b> EntryBuilder<'a, 'b, 'tcx> {
269 pub fn finish(self, def_id: DefId) {
270 if let Some((_, hasher)) = self.hcx {
271 let hash = hasher.finish();
272 self.ecx.metadata_hashes.push(EncodedMetadataHash {
273 def_index: def_id.index,
279 pub fn lazy<T>(&mut self, value: &T) -> Lazy<T>
280 where T: Encodable + HashStable<StableHashingContext<'b, 'tcx>>
282 if let Some((ref mut hcx, ref mut hasher)) = self.hcx {
283 value.hash_stable(hcx, hasher);
284 debug!("metadata-hash: {:?}", hasher);
289 pub fn lazy_seq<I, T>(&mut self, iter: I) -> LazySeq<T>
290 where I: IntoIterator<Item = T>,
291 T: Encodable + HashStable<StableHashingContext<'b, 'tcx>>
293 if let Some((ref mut hcx, ref mut hasher)) = self.hcx {
294 let iter = iter.into_iter();
295 let (lower_bound, upper_bound) = iter.size_hint();
297 if upper_bound == Some(lower_bound) {
298 lower_bound.hash_stable(hcx, hasher);
299 let mut num_items_hashed = 0;
300 let ret = self.ecx.lazy_seq(iter.inspect(|item| {
301 item.hash_stable(hcx, hasher);
302 num_items_hashed += 1;
305 // Sometimes items in a sequence are filtered out without being
306 // hashed (e.g. for &[ast::Attribute]) and this code path cannot
307 // handle that correctly, so we want to make sure we didn't hit
309 if lower_bound != num_items_hashed {
310 bug!("Hashed a different number of items ({}) than expected ({})",
314 debug!("metadata-hash: {:?}", hasher);
317 // Collect into a vec so we know the length of the sequence
318 let items: AccumulateVec<[T; 32]> = iter.collect();
319 items.hash_stable(hcx, hasher);
320 debug!("metadata-hash: {:?}", hasher);
321 self.ecx.lazy_seq(items)
324 self.ecx.lazy_seq(iter)
328 pub fn lazy_seq_from_slice<T>(&mut self, slice: &[T]) -> LazySeq<T>
329 where T: Encodable + HashStable<StableHashingContext<'b, 'tcx>>
331 if let Some((ref mut hcx, ref mut hasher)) = self.hcx {
332 slice.hash_stable(hcx, hasher);
333 debug!("metadata-hash: {:?}", hasher);
335 self.ecx.lazy_seq_ref(slice.iter())
338 pub fn lazy_seq_ref_from_slice<T>(&mut self, slice: &[&T]) -> LazySeq<T>
339 where T: Encodable + HashStable<StableHashingContext<'b, 'tcx>>
341 if let Some((ref mut hcx, ref mut hasher)) = self.hcx {
342 slice.hash_stable(hcx, hasher);
343 debug!("metadata-hash: {:?}", hasher);
345 self.ecx.lazy_seq_ref(slice.iter().map(|x| *x))