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;
48 crate mod constraint_set;
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(
117 if let Some(all_facts) = &mut all_facts {
120 .extend(universal_regions.universal_regions());
123 // Create the region inference context, taking ownership of the
124 // region inference data that was contained in `infcx`, and the
125 // base constraints generated by the type-check.
126 let var_origins = infcx.take_region_var_origins();
127 let MirTypeckRegionConstraints {
129 outlives_constraints,
132 let mut regioncx = RegionInferenceContext::new(
136 outlives_constraints,
140 // Generate various additional constraints.
141 constraint_generation::generate_constraints(
150 invalidation::generate_invalidates(
159 // Dump facts if requested.
160 let polonius_output = all_facts.and_then(|all_facts| {
161 if infcx.tcx.sess.opts.debugging_opts.nll_facts {
162 let def_path = infcx.tcx.hir.def_path(def_id);
164 PathBuf::from("nll-facts").join(def_path.to_filename_friendly_no_crate());
165 all_facts.write_to_dir(dir_path, location_table).unwrap();
168 if infcx.tcx.sess.opts.debugging_opts.polonius {
169 let algorithm = env::var("POLONIUS_ALGORITHM")
170 .unwrap_or(String::from("DatafrogOpt"));
171 let algorithm = Algorithm::from_str(&algorithm).unwrap();
172 debug!("compute_regions: using polonius algorithm {:?}", algorithm);
173 Some(Rc::new(Output::compute(
183 // Solve the region constraints.
184 let closure_region_requirements = regioncx.solve(infcx, &mir, def_id);
186 // Dump MIR results into a file, if that is enabled. This let us
187 // write unit-tests, as well as helping with debugging.
191 MirSource::item(def_id),
194 &closure_region_requirements,
197 // We also have a `#[rustc_nll]` annotation that causes us to dump
199 dump_annotation(infcx, &mir, def_id, ®ioncx, &closure_region_requirements);
201 (regioncx, polonius_output, closure_region_requirements)
204 fn dump_mir_results<'a, 'gcx, 'tcx>(
205 infcx: &InferCtxt<'a, 'gcx, 'tcx>,
206 liveness: &LivenessResults,
209 regioncx: &RegionInferenceContext,
210 closure_region_requirements: &Option<ClosureRegionRequirements>,
212 if !mir_util::dump_enabled(infcx.tcx, "nll", source) {
216 let regular_liveness_per_location: FxHashMap<_, _> = mir
220 let mut results = vec![];
223 .simulate_block(&mir, bb, |location, local_set| {
224 results.push((location, local_set.clone()));
230 let drop_liveness_per_location: FxHashMap<_, _> = mir
234 let mut results = vec![];
237 .simulate_block(&mir, bb, |location, local_set| {
238 results.push((location, local_set.clone()));
253 // Before the CFG, dump out the values for each region variable.
254 PassWhere::BeforeCFG => {
255 regioncx.dump_mir(out)?;
257 if let Some(closure_region_requirements) = closure_region_requirements {
259 writeln!(out, "| Free Region Constraints")?;
260 for_each_region_constraint(closure_region_requirements, &mut |msg| {
261 writeln!(out, "| {}", msg)
266 PassWhere::BeforeLocation(location) => {
267 let s = live_variable_set(
268 ®ular_liveness_per_location[&location],
269 &drop_liveness_per_location[&location],
273 "{:ALIGN$} | Live variables on entry to {:?}: {}",
281 // After each basic block, dump out the values
282 // that are live on exit from the basic block.
283 PassWhere::AfterTerminator(bb) => {
284 let s = live_variable_set(&liveness.regular.outs[bb], &liveness.drop.outs[bb]);
285 writeln!(out, " | Live variables on exit from {:?}: {}", bb, s)?;
288 PassWhere::BeforeBlock(_) | PassWhere::AfterLocation(_) | PassWhere::AfterCFG => {}
294 // Also dump the inference graph constraints as a graphviz file.
295 let _: io::Result<()> = do catch {
297 pretty::create_dump_file(infcx.tcx, "regioncx.dot", None, "nll", &0, source)?;
298 regioncx.dump_graphviz(&mut file)?;
302 fn dump_annotation<'a, 'gcx, 'tcx>(
303 infcx: &InferCtxt<'a, 'gcx, 'tcx>,
306 regioncx: &RegionInferenceContext,
307 closure_region_requirements: &Option<ClosureRegionRequirements>,
310 let base_def_id = tcx.closure_base_def_id(mir_def_id);
311 if !tcx.has_attr(base_def_id, "rustc_regions") {
315 // When the enclosing function is tagged with `#[rustc_regions]`,
316 // we dump out various bits of state as warnings. This is useful
317 // for verifying that the compiler is behaving as expected. These
318 // warnings focus on the closure region requirements -- for
319 // viewing the intraprocedural state, the -Zdump-mir output is
322 if let Some(closure_region_requirements) = closure_region_requirements {
326 .span_note_diag(mir.span, "External requirements");
328 regioncx.annotate(&mut err);
331 "number of external vids: {}",
332 closure_region_requirements.num_external_vids
335 // Dump the region constraints we are imposing *between* those
336 // newly created variables.
337 for_each_region_constraint(closure_region_requirements, &mut |msg| {
347 .span_note_diag(mir.span, "No external requirements");
348 regioncx.annotate(&mut err);
353 fn for_each_region_constraint(
354 closure_region_requirements: &ClosureRegionRequirements,
355 with_msg: &mut dyn FnMut(&str) -> io::Result<()>,
356 ) -> io::Result<()> {
357 for req in &closure_region_requirements.outlives_requirements {
358 let subject: &dyn Debug = match &req.subject {
359 ClosureOutlivesSubject::Region(subject) => subject,
360 ClosureOutlivesSubject::Ty(ty) => ty,
364 subject, req.outlived_free_region,
370 /// Right now, we piggy back on the `ReVar` to store our NLL inference
371 /// regions. These are indexed with `RegionVid`. This method will
372 /// assert that the region is a `ReVar` and extract its internal index.
373 /// This is reasonable because in our MIR we replace all universal regions
374 /// with inference variables.
375 pub trait ToRegionVid {
376 fn to_region_vid(self) -> RegionVid;
379 impl<'tcx> ToRegionVid for &'tcx RegionKind {
380 fn to_region_vid(self) -> RegionVid {
381 if let ty::ReVar(vid) = self {
384 bug!("region is not an ReVar: {:?}", self)
389 impl ToRegionVid for RegionVid {
390 fn to_region_vid(self) -> RegionVid {
395 fn live_variable_set(regular: &LocalSet, drops: &LocalSet) -> String {
396 // sort and deduplicate:
397 let all_locals: BTreeSet<_> = regular.iter().chain(drops.iter()).collect();
399 // construct a string with each local, including `(drop)` if it is
400 // only dropped, versus a regular use.
401 let mut string = String::new();
402 for local in all_locals {
403 string.push_str(&format!("{:?}", local));
405 if !regular.contains(&local) {
406 assert!(drops.contains(&local));
407 string.push_str(" (drop)");
410 string.push_str(", ");
413 let len = if string.is_empty() {
419 format!("[{}]", &string[..len])