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.
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 use borrow_check::borrow_set::BorrowSet;
12 use borrow_check::location::{LocationIndex, LocationTable};
13 use borrow_check::nll::facts::AllFactsExt;
14 use borrow_check::nll::type_check::MirTypeckRegionConstraints;
15 use dataflow::indexes::BorrowIndex;
16 use dataflow::move_paths::MoveData;
17 use dataflow::FlowAtLocation;
18 use dataflow::MaybeInitializedPlaces;
19 use rustc::hir::def_id::DefId;
20 use rustc::infer::InferCtxt;
21 use rustc::mir::{ClosureOutlivesSubject, ClosureRegionRequirements, Mir};
22 use rustc::ty::{self, RegionKind, RegionVid};
23 use rustc::util::nodemap::FxHashMap;
24 use std::collections::BTreeSet;
28 use std::path::PathBuf;
30 use std::str::FromStr;
31 use transform::MirSource;
32 use util::liveness::{LivenessResults, LocalSet};
34 use self::mir_util::PassWhere;
35 use polonius_engine::{Algorithm, Output};
37 use util::pretty::{self, ALIGN};
39 mod constraint_generation;
40 pub mod explain_borrow;
43 crate mod region_infer;
46 mod universal_regions;
50 use self::facts::AllFacts;
51 use self::region_infer::RegionInferenceContext;
52 use self::universal_regions::UniversalRegions;
54 /// Rewrites the regions in the MIR to use NLL variables, also
55 /// scraping out the set of universal regions (e.g., region parameters)
56 /// declared on the function. That set will need to be given to
57 /// `compute_regions`.
58 pub(in borrow_check) fn replace_regions_in_mir<'cx, 'gcx, 'tcx>(
59 infcx: &InferCtxt<'cx, 'gcx, 'tcx>,
61 param_env: ty::ParamEnv<'tcx>,
63 ) -> UniversalRegions<'tcx> {
64 debug!("replace_regions_in_mir(def_id={:?})", def_id);
66 // Compute named region information. This also renumbers the inputs/outputs.
67 let universal_regions = UniversalRegions::new(infcx, def_id, param_env);
69 // Replace all remaining regions with fresh inference variables.
70 renumber::renumber_mir(infcx, mir);
72 let source = MirSource::item(def_id);
73 mir_util::dump_mir(infcx.tcx, None, "renumber", &0, source, mir, |_, _| Ok(()));
78 /// Computes the (non-lexical) regions from the input MIR.
80 /// This may result in errors being reported.
81 pub(in borrow_check) fn compute_regions<'cx, 'gcx, 'tcx>(
82 infcx: &InferCtxt<'cx, 'gcx, 'tcx>,
84 universal_regions: UniversalRegions<'tcx>,
86 location_table: &LocationTable,
87 param_env: ty::ParamEnv<'gcx>,
88 flow_inits: &mut FlowAtLocation<MaybeInitializedPlaces<'cx, 'gcx, 'tcx>>,
89 move_data: &MoveData<'tcx>,
90 borrow_set: &BorrowSet<'tcx>,
92 RegionInferenceContext<'tcx>,
93 Option<Rc<Output<RegionVid, BorrowIndex, LocationIndex>>>,
94 Option<ClosureRegionRequirements<'gcx>>,
96 let mut all_facts = if AllFacts::enabled(infcx.tcx) {
97 Some(AllFacts::default())
102 // Run the MIR type-checker.
103 let liveness = &LivenessResults::compute(mir);
104 let constraint_sets = type_check::type_check(
118 if let Some(all_facts) = &mut all_facts {
121 .extend(universal_regions.universal_regions());
124 // Create the region inference context, taking ownership of the
125 // region inference data that was contained in `infcx`, and the
126 // base constraints generated by the type-check.
127 let var_origins = infcx.take_region_var_origins();
128 let MirTypeckRegionConstraints {
130 outlives_constraints,
133 let mut regioncx = RegionInferenceContext::new(
137 outlives_constraints,
141 // Generate various additional constraints.
142 constraint_generation::generate_constraints(
151 invalidation::generate_invalidates(
160 // Dump facts if requested.
161 let polonius_output = all_facts.and_then(|all_facts| {
162 if infcx.tcx.sess.opts.debugging_opts.nll_facts {
163 let def_path = infcx.tcx.hir.def_path(def_id);
165 PathBuf::from("nll-facts").join(def_path.to_filename_friendly_no_crate());
166 all_facts.write_to_dir(dir_path, location_table).unwrap();
169 if infcx.tcx.sess.opts.debugging_opts.polonius {
170 let algorithm = env::var("POLONIUS_ALGORITHM")
171 .unwrap_or(String::from("DatafrogOpt"));
172 let algorithm = Algorithm::from_str(&algorithm).unwrap();
173 debug!("compute_regions: using polonius algorithm {:?}", algorithm);
174 Some(Rc::new(Output::compute(
184 // Solve the region constraints.
185 let closure_region_requirements = regioncx.solve(infcx, &mir, def_id);
187 // Dump MIR results into a file, if that is enabled. This let us
188 // write unit-tests, as well as helping with debugging.
192 MirSource::item(def_id),
195 &closure_region_requirements,
198 // We also have a `#[rustc_nll]` annotation that causes us to dump
200 dump_annotation(infcx, &mir, def_id, ®ioncx, &closure_region_requirements);
202 (regioncx, polonius_output, closure_region_requirements)
205 fn dump_mir_results<'a, 'gcx, 'tcx>(
206 infcx: &InferCtxt<'a, 'gcx, 'tcx>,
207 liveness: &LivenessResults,
210 regioncx: &RegionInferenceContext,
211 closure_region_requirements: &Option<ClosureRegionRequirements>,
213 if !mir_util::dump_enabled(infcx.tcx, "nll", source) {
217 let regular_liveness_per_location: FxHashMap<_, _> = mir
221 let mut results = vec![];
224 .simulate_block(&mir, bb, |location, local_set| {
225 results.push((location, local_set.clone()));
231 let drop_liveness_per_location: FxHashMap<_, _> = mir
235 let mut results = vec![];
238 .simulate_block(&mir, bb, |location, local_set| {
239 results.push((location, local_set.clone()));
254 // Before the CFG, dump out the values for each region variable.
255 PassWhere::BeforeCFG => {
256 regioncx.dump_mir(out)?;
258 if let Some(closure_region_requirements) = closure_region_requirements {
260 writeln!(out, "| Free Region Constraints")?;
261 for_each_region_constraint(closure_region_requirements, &mut |msg| {
262 writeln!(out, "| {}", msg)
267 PassWhere::BeforeLocation(location) => {
268 let s = live_variable_set(
269 ®ular_liveness_per_location[&location],
270 &drop_liveness_per_location[&location],
274 "{:ALIGN$} | Live variables on entry to {:?}: {}",
282 // After each basic block, dump out the values
283 // that are live on exit from the basic block.
284 PassWhere::AfterTerminator(bb) => {
285 let s = live_variable_set(&liveness.regular.outs[bb], &liveness.drop.outs[bb]);
286 writeln!(out, " | Live variables on exit from {:?}: {}", bb, s)?;
289 PassWhere::BeforeBlock(_) | PassWhere::AfterLocation(_) | PassWhere::AfterCFG => {}
295 // Also dump the inference graph constraints as a graphviz file.
296 let _: io::Result<()> = do catch {
298 pretty::create_dump_file(infcx.tcx, "regioncx.dot", None, "nll", &0, source)?;
299 regioncx.dump_graphviz_raw_constraints(&mut file)?;
303 fn dump_annotation<'a, 'gcx, 'tcx>(
304 infcx: &InferCtxt<'a, 'gcx, 'tcx>,
307 regioncx: &RegionInferenceContext,
308 closure_region_requirements: &Option<ClosureRegionRequirements>,
311 let base_def_id = tcx.closure_base_def_id(mir_def_id);
312 if !tcx.has_attr(base_def_id, "rustc_regions") {
316 // When the enclosing function is tagged with `#[rustc_regions]`,
317 // we dump out various bits of state as warnings. This is useful
318 // for verifying that the compiler is behaving as expected. These
319 // warnings focus on the closure region requirements -- for
320 // viewing the intraprocedural state, the -Zdump-mir output is
323 if let Some(closure_region_requirements) = closure_region_requirements {
327 .span_note_diag(mir.span, "External requirements");
329 regioncx.annotate(&mut err);
332 "number of external vids: {}",
333 closure_region_requirements.num_external_vids
336 // Dump the region constraints we are imposing *between* those
337 // newly created variables.
338 for_each_region_constraint(closure_region_requirements, &mut |msg| {
348 .span_note_diag(mir.span, "No external requirements");
349 regioncx.annotate(&mut err);
354 fn for_each_region_constraint(
355 closure_region_requirements: &ClosureRegionRequirements,
356 with_msg: &mut dyn FnMut(&str) -> io::Result<()>,
357 ) -> io::Result<()> {
358 for req in &closure_region_requirements.outlives_requirements {
359 let subject: &dyn Debug = match &req.subject {
360 ClosureOutlivesSubject::Region(subject) => subject,
361 ClosureOutlivesSubject::Ty(ty) => ty,
365 subject, req.outlived_free_region,
371 /// Right now, we piggy back on the `ReVar` to store our NLL inference
372 /// regions. These are indexed with `RegionVid`. This method will
373 /// assert that the region is a `ReVar` and extract its internal index.
374 /// This is reasonable because in our MIR we replace all universal regions
375 /// with inference variables.
376 pub trait ToRegionVid {
377 fn to_region_vid(self) -> RegionVid;
380 impl<'tcx> ToRegionVid for &'tcx RegionKind {
381 fn to_region_vid(self) -> RegionVid {
382 if let ty::ReVar(vid) = self {
385 bug!("region is not an ReVar: {:?}", self)
390 impl ToRegionVid for RegionVid {
391 fn to_region_vid(self) -> RegionVid {
396 fn live_variable_set(regular: &LocalSet, drops: &LocalSet) -> String {
397 // sort and deduplicate:
398 let all_locals: BTreeSet<_> = regular.iter().chain(drops.iter()).collect();
400 // construct a string with each local, including `(drop)` if it is
401 // only dropped, versus a regular use.
402 let mut string = String::new();
403 for local in all_locals {
404 string.push_str(&format!("{:?}", local));
406 if !regular.contains(&local) {
407 assert!(drops.contains(&local));
408 string.push_str(" (drop)");
411 string.push_str(", ");
414 let len = if string.is_empty() {
420 format!("[{}]", &string[..len])