implement liveness tracing, remove old liveness system

Author: nikomatsakis

src/librustc/mir/mod.rs

@@ -194,12 +194,12 @@ impl<'tcx> Mir<'tcx> {
     }
 
     #[inline]
-    pub fn predecessors(&self) -> ReadGuard<IndexVec<BasicBlock, Vec<BasicBlock>>> {
+    pub fn predecessors(&self) -> ReadGuard<'_, IndexVec<BasicBlock, Vec<BasicBlock>>> {
         self.cache.predecessors(self)
     }
 
     #[inline]
-    pub fn predecessors_for(&self, bb: BasicBlock) -> ReadGuard<Vec<BasicBlock>> {
+    pub fn predecessors_for(&self, bb: BasicBlock) -> ReadGuard<'_, Vec<BasicBlock>> {
         ReadGuard::map(self.predecessors(), |p| &p[bb])
     }
 
@@ -328,6 +328,14 @@ impl<'tcx> Mir<'tcx> {
     pub fn return_ty(&self) -> Ty<'tcx> {
         self.local_decls[RETURN_PLACE].ty
     }
+
+    /// Get the location of the terminator for the given block
+    pub fn terminator_loc(&self, bb: BasicBlock) -> Location {
+        Location {
+            block: bb,
+            statement_index: self[bb].statements.len(),
+        }
+    }
 }
 
 #[derive(Copy, Clone, Debug, RustcEncodable, RustcDecodable)]

src/librustc_data_structures/lib.rs

@@ -20,6 +20,7 @@
       html_favicon_url = "https://www.rust-lang.org/favicon.ico",
       html_root_url = "https://doc.rust-lang.org/nightly/")]
 
+#![feature(in_band_lifetimes)]
 #![feature(unboxed_closures)]
 #![feature(fn_traits)]
 #![feature(unsize)]
@@ -77,6 +78,7 @@ pub mod tiny_list;
 pub mod transitive_relation;
 pub mod tuple_slice;
 pub use ena::unify;
+pub mod vec_linked_list;
 pub mod work_queue;
 
 pub struct OnDrop<F: Fn()>(pub F);

src/librustc_data_structures/vec_linked_list.rs

@@ -0,0 +1,83 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use indexed_vec::{Idx, IndexVec};
+
+pub fn iter<Ls>(
+    first: Option<Ls::LinkIndex>,
+    links: &'a Ls,
+) -> impl Iterator<Item = Ls::LinkIndex> + 'a
+where
+    Ls: Links,
+{
+    VecLinkedListIterator {
+        links: links,
+        current: first,
+    }
+}
+
+pub struct VecLinkedListIterator<Ls>
+where
+    Ls: Links,
+{
+    links: Ls,
+    current: Option<Ls::LinkIndex>,
+}
+
+impl<Ls> Iterator for VecLinkedListIterator<Ls>
+where
+    Ls: Links,
+{
+    type Item = Ls::LinkIndex;
+
+    fn next(&mut self) -> Option<Ls::LinkIndex> {
+        if let Some(c) = self.current {
+            self.current = <Ls as Links>::next(&self.links, c);
+            Some(c)
+        } else {
+            None
+        }
+    }
+}
+
+pub trait Links {
+    type LinkIndex: Copy;
+
+    fn next(links: &Self, index: Self::LinkIndex) -> Option<Self::LinkIndex>;
+}
+
+impl<Ls> Links for &Ls
+where
+    Ls: Links,
+{
+    type LinkIndex = Ls::LinkIndex;
+
+    fn next(links: &Self, index: Ls::LinkIndex) -> Option<Ls::LinkIndex> {
+        <Ls as Links>::next(links, index)
+    }
+}
+
+pub trait LinkElem {
+    type LinkIndex: Copy;
+
+    fn next(elem: &Self) -> Option<Self::LinkIndex>;
+}
+
+impl<L, E> Links for IndexVec<L, E>
+where
+    E: LinkElem<LinkIndex = L>,
+    L: Idx,
+{
+    type LinkIndex = L;
+
+    fn next(links: &Self, index: L) -> Option<L> {
+        <E as LinkElem>::next(&links[index])
+    }
+}

src/librustc_mir/borrow_check/flows.rs

@@ -89,6 +89,10 @@ impl<'b, 'gcx, 'tcx> FlowsAtLocation for Flows<'b, 'gcx, 'tcx> {
         each_flow!(self, reset_to_entry_of(bb));
     }
 
+    fn reset_to_exit_of(&mut self, bb: BasicBlock) {
+        each_flow!(self, reset_to_exit_of(bb));
+    }
+
     fn reconstruct_statement_effect(&mut self, location: Location) {
         each_flow!(self, reconstruct_statement_effect(location));
     }

src/librustc_mir/borrow_check/nll/mod.rs

@@ -12,7 +12,7 @@ use borrow_check::borrow_set::BorrowSet;
 use borrow_check::location::{LocationIndex, LocationTable};
 use borrow_check::nll::facts::AllFactsExt;
 use borrow_check::nll::type_check::{MirTypeckResults, MirTypeckRegionConstraints};
-use borrow_check::nll::type_check::liveness::liveness_map::{NllLivenessMap, LocalWithRegion};
+use borrow_check::nll::type_check::liveness::liveness_map::NllLivenessMap;
 use borrow_check::nll::region_infer::values::RegionValueElements;
 use dataflow::indexes::BorrowIndex;
 use dataflow::move_paths::MoveData;
@@ -22,22 +22,19 @@ use rustc::hir::def_id::DefId;
 use rustc::infer::InferCtxt;
 use rustc::mir::{ClosureOutlivesSubject, ClosureRegionRequirements, Mir};
 use rustc::ty::{self, RegionKind, RegionVid};
-use rustc::util::nodemap::FxHashMap;
 use rustc_errors::Diagnostic;
-use std::collections::BTreeSet;
 use std::fmt::Debug;
 use std::env;
 use std::io;
 use std::path::PathBuf;
 use std::rc::Rc;
 use std::str::FromStr;
 use transform::MirSource;
-use util::liveness::{LivenessResults, LiveVarSet};
 
 use self::mir_util::PassWhere;
 use polonius_engine::{Algorithm, Output};
 use util as mir_util;
-use util::pretty::{self, ALIGN};
+use util::pretty;
 
 mod constraint_generation;
 pub mod explain_borrow;
@@ -111,8 +108,6 @@ pub(in borrow_check) fn compute_regions<'cx, 'gcx, 'tcx>(
     let MirTypeckResults {
         constraints,
         universal_region_relations,
-        liveness,
-        liveness_map,
     } = type_check::type_check(
         infcx,
         param_env,
@@ -205,8 +200,6 @@ pub(in borrow_check) fn compute_regions<'cx, 'gcx, 'tcx>(
     // write unit-tests, as well as helping with debugging.
     dump_mir_results(
         infcx,
-        &liveness,
-        &liveness_map,
         MirSource::item(def_id),
         &mir,
         &regioncx,
@@ -222,8 +215,6 @@ pub(in borrow_check) fn compute_regions<'cx, 'gcx, 'tcx>(
 
 fn dump_mir_results<'a, 'gcx, 'tcx>(
     infcx: &InferCtxt<'a, 'gcx, 'tcx>,
-    liveness: &LivenessResults<LocalWithRegion>,
-    liveness_map: &NllLivenessMap,
     source: MirSource,
     mir: &Mir<'tcx>,
     regioncx: &RegionInferenceContext,
@@ -233,34 +224,6 @@ fn dump_mir_results<'a, 'gcx, 'tcx>(
         return;
     }
 
-    let regular_liveness_per_location: FxHashMap<_, _> = mir
-        .basic_blocks()
-        .indices()
-        .flat_map(|bb| {
-            let mut results = vec![];
-            liveness
-                .regular
-                .simulate_block(&mir, bb, liveness_map, |location, local_set| {
-                    results.push((location, local_set.clone()));
-                });
-            results
-        })
-        .collect();
-
-    let drop_liveness_per_location: FxHashMap<_, _> = mir
-        .basic_blocks()
-        .indices()
-        .flat_map(|bb| {
-            let mut results = vec![];
-            liveness
-                .drop
-                .simulate_block(&mir, bb, liveness_map, |location, local_set| {
-                    results.push((location, local_set.clone()));
-                });
-            results
-        })
-        .collect();
-
     mir_util::dump_mir(
         infcx.tcx,
         None,
@@ -283,26 +246,10 @@ fn dump_mir_results<'a, 'gcx, 'tcx>(
                     }
                 }
 
-                PassWhere::BeforeLocation(location) => {
-                    let s = live_variable_set(
-                        &regular_liveness_per_location[&location],
-                        &drop_liveness_per_location[&location],
-                    );
-                    writeln!(
-                        out,
-                        "{:ALIGN$} | Live variables on entry to {:?}: {}",
-                        "",
-                        location,
-                        s,
-                        ALIGN = ALIGN
-                    )?;
+                PassWhere::BeforeLocation(_) => {
                 }
 
-                // After each basic block, dump out the values
-                // that are live on exit from the basic block.
-                PassWhere::AfterTerminator(bb) => {
-                    let s = live_variable_set(&liveness.regular.outs[bb], &liveness.drop.outs[bb]);
-                    writeln!(out, "    | Live variables on exit from {:?}: {}", bb, s)?;
+                PassWhere::AfterTerminator(_) => {
                 }
 
                 PassWhere::BeforeBlock(_) | PassWhere::AfterLocation(_) | PassWhere::AfterCFG => {}
@@ -420,33 +367,3 @@ impl ToRegionVid for RegionVid {
         self
     }
 }
-
-fn live_variable_set(
-    regular: &LiveVarSet<LocalWithRegion>,
-    drops: &LiveVarSet<LocalWithRegion>
-) -> String {
-    // sort and deduplicate:
-    let all_locals: BTreeSet<_> = regular.iter().chain(drops.iter()).collect();
-
-    // construct a string with each local, including `(drop)` if it is
-    // only dropped, versus a regular use.
-    let mut string = String::new();
-    for local in all_locals {
-        string.push_str(&format!("{:?}", local));
-
-        if !regular.contains(&local) {
-            assert!(drops.contains(&local));
-            string.push_str(" (drop)");
-        }
-
-        string.push_str(", ");
-    }
-
-    let len = if string.is_empty() {
-        0
-    } else {
-        string.len() - 2
-    };
-
-    format!("[{}]", &string[..len])
-}

src/librustc_mir/borrow_check/nll/region_infer/values.rs

@@ -10,7 +10,7 @@
 
 use rustc::mir::{BasicBlock, Location, Mir};
 use rustc::ty::{self, RegionVid};
-use rustc_data_structures::bitvec::SparseBitMatrix;
+use rustc_data_structures::bitvec::{BitArray, SparseBitMatrix};
 use rustc_data_structures::indexed_vec::Idx;
 use rustc_data_structures::indexed_vec::IndexVec;
 use std::fmt::Debug;
@@ -47,8 +47,13 @@ impl RegionValueElements {
         }
     }
 
+    /// Total number of point indices
+    crate fn num_points(&self) -> usize {
+        self.num_points
+    }
+
     /// Converts a `Location` into a `PointIndex`. O(1).
-    fn point_from_location(&self, location: Location) -> PointIndex {
+    crate fn point_from_location(&self, location: Location) -> PointIndex {
         let Location {
             block,
             statement_index,
@@ -57,6 +62,12 @@ impl RegionValueElements {
         PointIndex::new(start_index + statement_index)
     }
 
+    /// Converts a `Location` into a `PointIndex`. O(1).
+    crate fn entry_point(&self, block: BasicBlock) -> PointIndex {
+        let start_index = self.statements_before_block[block];
+        PointIndex::new(start_index)
+    }
+
     /// Converts a `PointIndex` back to a location. O(N) where N is
     /// the number of blocks; could be faster if we ever cared.
     crate fn to_location(&self, i: PointIndex) -> Location {
@@ -92,6 +103,15 @@ impl RegionValueElements {
             statement_index: point_index - first_index,
         }
     }
+
+    /// Returns an iterator of each basic block and the first point
+    /// index within the block; the point indices for all statements
+    /// within the block follow afterwards.
+    crate fn head_indices(&self) -> impl Iterator<Item = (BasicBlock, PointIndex)> + '_ {
+        self.statements_before_block
+            .iter_enumerated()
+            .map(move |(bb, &first_index)| (bb, PointIndex::new(first_index)))
+    }
 }
 
 /// A single integer representing a `Location` in the MIR control-flow
@@ -151,6 +171,13 @@ impl<N: Idx> LivenessValues<N> {
         self.points.add(row, index)
     }
 
+    /// Adds all the elements in the given bit array into the given
+    /// region. Returns true if any of them are newly added.
+    crate fn add_elements(&mut self, row: N, locations: &BitArray<PointIndex>) -> bool {
+        debug!("LivenessValues::add_elements(row={:?}, locations={:?})", row, locations);
+        self.points.merge_into(row, locations)
+    }
+
     /// Adds all the control-flow points to the values for `r`.
     crate fn add_all_points(&mut self, row: N) {
         self.points.add_all(row);
@@ -366,6 +393,18 @@ impl ToElementIndex for ty::UniverseIndex {
     }
 }
 
+crate fn location_set_str(
+    elements: &RegionValueElements,
+    points: impl IntoIterator<Item = PointIndex>,
+) -> String {
+    region_value_str(
+        points
+            .into_iter()
+            .map(|p| elements.to_location(p))
+            .map(RegionElement::Location),
+    )
+}
+
 fn region_value_str(elements: impl IntoIterator<Item = RegionElement>) -> String {
     let mut result = String::new();
     result.push_str("{");