/
mod.rs
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/
mod.rs
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// Copyright 2017 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 borrow_check::nll::{NllLivenessMap, LocalWithRegion};
use borrow_check::nll::type_check::AtLocation;
use dataflow::move_paths::{HasMoveData, MoveData};
use dataflow::MaybeInitializedPlaces;
use dataflow::{FlowAtLocation, FlowsAtLocation};
use rustc::infer::canonical::QueryRegionConstraint;
use rustc::mir::{BasicBlock, Location, Mir};
use rustc::traits::query::dropck_outlives::DropckOutlivesResult;
use rustc::traits::query::type_op::outlives::DropckOutlives;
use rustc::traits::query::type_op::TypeOp;
use rustc::ty::{Ty, TypeFoldable};
use rustc_data_structures::fx::FxHashMap;
use std::rc::Rc;
use util::liveness::{LivenessResults, LiveVariableMap };
use super::TypeChecker;
crate mod liveness_map;
/// Combines liveness analysis with initialization analysis to
/// determine which variables are live at which points, both due to
/// ordinary uses and drops. Returns a set of (ty, location) pairs
/// that indicate which types must be live at which point in the CFG.
/// This vector is consumed by `constraint_generation`.
///
/// NB. This computation requires normalization; therefore, it must be
/// performed before
pub(super) fn generate<'gcx, 'tcx>(
cx: &mut TypeChecker<'_, 'gcx, 'tcx>,
mir: &Mir<'tcx>,
flow_inits: &mut FlowAtLocation<MaybeInitializedPlaces<'_, 'gcx, 'tcx>>,
move_data: &MoveData<'tcx>,
) -> (LivenessResults<LocalWithRegion>, NllLivenessMap) {
let liveness_map = NllLivenessMap::compute(&mir);
let liveness = LivenessResults::compute(mir, &liveness_map);
{
let mut generator = TypeLivenessGenerator {
cx,
mir,
liveness: &liveness,
flow_inits,
move_data,
drop_data: FxHashMap(),
map: &liveness_map,
};
for bb in mir.basic_blocks().indices() {
generator.add_liveness_constraints(bb);
}
}
(liveness, liveness_map)
}
struct TypeLivenessGenerator<'gen, 'typeck, 'flow, 'gcx, 'tcx>
where
'typeck: 'gen,
'flow: 'gen,
'tcx: 'typeck + 'flow,
'gcx: 'tcx,
{
cx: &'gen mut TypeChecker<'typeck, 'gcx, 'tcx>,
mir: &'gen Mir<'tcx>,
liveness: &'gen LivenessResults<LocalWithRegion>,
flow_inits: &'gen mut FlowAtLocation<MaybeInitializedPlaces<'flow, 'gcx, 'tcx>>,
move_data: &'gen MoveData<'tcx>,
drop_data: FxHashMap<Ty<'tcx>, DropData<'tcx>>,
map: &'gen NllLivenessMap,
}
struct DropData<'tcx> {
dropck_result: DropckOutlivesResult<'tcx>,
region_constraint_data: Option<Rc<Vec<QueryRegionConstraint<'tcx>>>>,
}
impl<'gen, 'typeck, 'flow, 'gcx, 'tcx> TypeLivenessGenerator<'gen, 'typeck, 'flow, 'gcx, 'tcx> {
/// Liveness constraints:
///
/// > If a variable V is live at point P, then all regions R in the type of V
/// > must include the point P.
fn add_liveness_constraints(&mut self, bb: BasicBlock) {
debug!("add_liveness_constraints(bb={:?})", bb);
self.liveness
.regular
.simulate_block(self.mir, bb, self.map, |location, live_locals| {
for live_local in live_locals.iter() {
let local = self.map.from_live_var(live_local);
let live_local_ty = self.mir.local_decls[local].ty;
Self::push_type_live_constraint(&mut self.cx, live_local_ty, location);
}
});
let mut all_live_locals: Vec<(Location, Vec<LocalWithRegion>)> = vec![];
self.liveness
.drop
.simulate_block(self.mir, bb, self.map, |location, live_locals| {
all_live_locals.push((location, live_locals.iter().collect()));
});
debug!(
"add_liveness_constraints: all_live_locals={:#?}",
all_live_locals
);
let terminator_index = self.mir.basic_blocks()[bb].statements.len();
self.flow_inits.reset_to_entry_of(bb);
while let Some((location, live_locals)) = all_live_locals.pop() {
for live_local in live_locals {
debug!(
"add_liveness_constraints: location={:?} live_local={:?}",
location, live_local
);
if log_enabled!(::log::Level::Debug) {
self.flow_inits.each_state_bit(|mpi_init| {
debug!(
"add_liveness_constraints: location={:?} initialized={:?}",
location,
&self.flow_inits.operator().move_data().move_paths[mpi_init]
);
});
}
let local = self.map.from_live_var(live_local);
let mpi = self.move_data.rev_lookup.find_local(local);
if let Some(initialized_child) = self.flow_inits.has_any_child_of(mpi) {
debug!(
"add_liveness_constraints: mpi={:?} has initialized child {:?}",
self.move_data.move_paths[mpi],
self.move_data.move_paths[initialized_child]
);
let local = self.map.from_live_var(live_local);
let live_local_ty = self.mir.local_decls[local].ty;
self.add_drop_live_constraint(live_local, live_local_ty, location);
}
}
if location.statement_index == terminator_index {
debug!(
"add_liveness_constraints: reconstruct_terminator_effect from {:#?}",
location
);
self.flow_inits.reconstruct_terminator_effect(location);
} else {
debug!(
"add_liveness_constraints: reconstruct_statement_effect from {:#?}",
location
);
self.flow_inits.reconstruct_statement_effect(location);
}
self.flow_inits.apply_local_effect(location);
}
}
/// Some variable with type `live_ty` is "regular live" at
/// `location` -- i.e., it may be used later. This means that all
/// regions appearing in the type `live_ty` must be live at
/// `location`.
fn push_type_live_constraint<T>(
cx: &mut TypeChecker<'_, 'gcx, 'tcx>,
value: T,
location: Location,
) where
T: TypeFoldable<'tcx>,
{
debug!(
"push_type_live_constraint(live_ty={:?}, location={:?})",
value, location
);
cx.tcx().for_each_free_region(&value, |live_region| {
if let Some(ref mut borrowck_context) = cx.borrowck_context {
let region_vid = borrowck_context.universal_regions.to_region_vid(live_region);
borrowck_context.constraints.liveness_constraints.add_element(region_vid, location);
if let Some(all_facts) = borrowck_context.all_facts {
let start_index = borrowck_context.location_table.start_index(location);
all_facts.region_live_at.push((region_vid, start_index));
let mid_index = borrowck_context.location_table.mid_index(location);
all_facts.region_live_at.push((region_vid, mid_index));
}
}
});
}
/// Some variable with type `live_ty` is "drop live" at `location`
/// -- i.e., it may be dropped later. This means that *some* of
/// the regions in its type must be live at `location`. The
/// precise set will depend on the dropck constraints, and in
/// particular this takes `#[may_dangle]` into account.
fn add_drop_live_constraint(
&mut self,
dropped_local: LocalWithRegion,
dropped_ty: Ty<'tcx>,
location: Location,
) {
debug!(
"add_drop_live_constraint(dropped_local={:?}, dropped_ty={:?}, location={:?})",
dropped_local, dropped_ty, location
);
let drop_data = self.drop_data.entry(dropped_ty).or_insert_with({
let cx = &mut self.cx;
move || Self::compute_drop_data(cx, dropped_ty)
});
if let Some(data) = &drop_data.region_constraint_data {
self.cx.push_region_constraints(location.boring(), data);
}
drop_data.dropck_result.report_overflows(
self.cx.infcx.tcx,
self.mir.source_info(location).span,
dropped_ty,
);
// All things in the `outlives` array may be touched by
// the destructor and must be live at this point.
for &kind in &drop_data.dropck_result.kinds {
Self::push_type_live_constraint(&mut self.cx, kind, location);
}
}
fn compute_drop_data(
cx: &mut TypeChecker<'_, 'gcx, 'tcx>,
dropped_ty: Ty<'tcx>,
) -> DropData<'tcx> {
debug!("compute_drop_data(dropped_ty={:?})", dropped_ty,);
let param_env = cx.param_env;
let (dropck_result, region_constraint_data) = param_env
.and(DropckOutlives::new(dropped_ty))
.fully_perform(cx.infcx)
.unwrap();
DropData {
dropck_result,
region_constraint_data,
}
}
}