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Refactored DFS to be much cleaner. Added continue after noting that b…
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…orrow is out of scope at location.
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@davidtwco
davidtwco committed May 29, 2018
1 parent 24ee506 commit 4500fe0
Showing 1 changed file with 27 additions and 99 deletions.
126 changes: 27 additions & 99 deletions src/librustc_mir/dataflow/impls/borrows.rs
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Expand Up @@ -15,13 +15,13 @@ use rustc;
use rustc::hir;
use rustc::hir::def_id::DefId;
use rustc::middle::region;
use rustc::mir::{self, Location, Place, Mir, TerminatorKind};
use rustc::mir::{self, Location, Place, Mir};
use rustc::ty::TyCtxt;
use rustc::ty::{RegionKind, RegionVid};
use rustc::ty::RegionKind::ReScope;

use rustc_data_structures::bitslice::BitwiseOperator;
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_data_structures::indexed_set::IdxSet;
use rustc_data_structures::indexed_vec::IndexVec;
use rustc_data_structures::sync::Lrc;
Expand Down Expand Up @@ -60,104 +60,33 @@ fn precompute_borrows_out_of_scope<'a, 'tcx>(
borrow_index: BorrowIndex,
borrow_region: RegionVid,
location: Location,
visited_locations: &mut Vec<Location>
) {
// Check if we have already visited this location and skip
// it if we have - avoids infinite loops.
if visited_locations.contains(&location) { return; }
visited_locations.push(location.clone());

// Next, add the borrow index to the current location's vector if the region does
// not contain the point at that location (or create a new vector if required).
if !regioncx.region_contains_point(borrow_region, location) {
borrows_out_of_scope_at_location
.entry(location.clone())
.and_modify(|m| m.push(borrow_index))
.or_insert(vec![ borrow_index ]);
}
// Keep track of places we've locations to check and locations that we have checked.
let mut stack = vec![ location ];
let mut visited = FxHashSet();
visited.insert(location);

while let Some(location) = stack.pop() {
// If region does not contain a point at the location, then add to list and skip
// successor locations.
if !regioncx.region_contains_point(borrow_region, location) {
borrows_out_of_scope_at_location
.entry(location)
.or_insert(vec![])
.push(borrow_index);
continue;
}

let bb_data = &mir[location.block];
// If we are past the last statement, then check the terminator
// to determine which location to proceed to.
if location.statement_index == bb_data.statements.len() {
// Add successors to locations to visit, if not visited before.
let bb_data = &mir[location.block];
if let Some(ref terminator) = bb_data.terminator {
match terminator.kind {
TerminatorKind::Goto { target } |
TerminatorKind::FalseEdges { real_target: target, .. } |
TerminatorKind::FalseUnwind { real_target: target, .. } => {
precompute_borrows_out_of_scope(
mir, regioncx, borrows_out_of_scope_at_location,
borrow_index, borrow_region, target.start_location(),
visited_locations
);
},
TerminatorKind::SwitchInt { ref targets, .. } => {
for block in targets {
precompute_borrows_out_of_scope(
mir, regioncx, borrows_out_of_scope_at_location,
borrow_index, borrow_region, block.start_location(),
visited_locations
);
}
},
TerminatorKind::Drop { target, unwind, .. } |
TerminatorKind::DropAndReplace { target, unwind, .. } => {
precompute_borrows_out_of_scope(
mir, regioncx, borrows_out_of_scope_at_location,
borrow_index, borrow_region, target.start_location(),
visited_locations
);

if let Some(unwind_block) = unwind {
precompute_borrows_out_of_scope(
mir, regioncx, borrows_out_of_scope_at_location,
borrow_index, borrow_region, unwind_block.start_location(),
visited_locations
);
}
},
TerminatorKind::Call { ref destination, cleanup, .. } => {
if let Some((_, block)) = destination {
precompute_borrows_out_of_scope(
mir, regioncx, borrows_out_of_scope_at_location,
borrow_index, borrow_region, block.start_location(),
visited_locations
);
}

if let Some(block) = cleanup {
precompute_borrows_out_of_scope(
mir, regioncx, borrows_out_of_scope_at_location,
borrow_index, borrow_region, block.start_location(),
visited_locations
);
}
},
TerminatorKind::Assert { target, cleanup, .. } |
TerminatorKind::Yield { resume: target, drop: cleanup, .. } => {
precompute_borrows_out_of_scope(
mir, regioncx, borrows_out_of_scope_at_location,
borrow_index, borrow_region, target.start_location(),
visited_locations
);

if let Some(block) = cleanup {
precompute_borrows_out_of_scope(
mir, regioncx, borrows_out_of_scope_at_location,
borrow_index, borrow_region, block.start_location(),
visited_locations
);
}
},
_ => {},
};
};
// If we're not on the last statement, then go to the next
// statement in this block.
} else {
precompute_borrows_out_of_scope(mir, regioncx, borrows_out_of_scope_at_location,
borrow_index, borrow_region,
location.successor_within_block(), visited_locations);
for block in terminator.successors() {
let loc = block.start_location();
if visited.insert(loc) {
stack.push(loc);
}
}
}
}
}

Expand All @@ -182,8 +111,7 @@ impl<'a, 'gcx, 'tcx> Borrows<'a, 'gcx, 'tcx> {

precompute_borrows_out_of_scope(mir, &nonlexical_regioncx,
&mut borrows_out_of_scope_at_location,
borrow_index, borrow_region, location,
&mut Vec::new());
borrow_index, borrow_region, location);
}

Borrows {
Expand Down

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