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Ensure that depth first search does not get stuck in cycles.

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This commit is contained in:
David Wood 2018-05-27 22:26:10 +01:00
parent 0eeebe1795
commit 24ee506913
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GPG Key ID: 01760B4F9F53F154
1 changed files with 28 additions and 12 deletions
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40
src/librustc_mir/dataflow/impls/borrows.rs
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@ -59,9 +59,16 @@ fn precompute_borrows_out_of_scope<'a, 'tcx>(
borrows_out_of_scope_at_location: &mut FxHashMap<Location, Vec<BorrowIndex>>,
borrow_index: BorrowIndex,
borrow_region: RegionVid,
location: Location
location: Location,
visited_locations: &mut Vec<Location>
) {
// Start by dealing with the current 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())
@ -80,14 +87,16 @@ fn precompute_borrows_out_of_scope<'a, 'tcx>(
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()
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()
borrow_index, borrow_region, block.start_location(),
visited_locations
);
}
},
@ -95,13 +104,15 @@ fn precompute_borrows_out_of_scope<'a, 'tcx>(
TerminatorKind::DropAndReplace { target, unwind, .. } => {
precompute_borrows_out_of_scope(
mir, regioncx, borrows_out_of_scope_at_location,
borrow_index, borrow_region, target.start_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()
borrow_index, borrow_region, unwind_block.start_location(),
visited_locations
);
}
},
@ -109,14 +120,16 @@ fn precompute_borrows_out_of_scope<'a, 'tcx>(
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()
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()
borrow_index, borrow_region, block.start_location(),
visited_locations
);
}
},
@ -124,13 +137,15 @@ fn precompute_borrows_out_of_scope<'a, 'tcx>(
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()
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()
borrow_index, borrow_region, block.start_location(),
visited_locations
);
}
},
@ -142,7 +157,7 @@ fn precompute_borrows_out_of_scope<'a, 'tcx>(
} else {
precompute_borrows_out_of_scope(mir, regioncx, borrows_out_of_scope_at_location,
borrow_index, borrow_region,
location.successor_within_block());
location.successor_within_block(), visited_locations);
}
}
@ -167,7 +182,8 @@ 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);
borrow_index, borrow_region, location,
&mut Vec::new());
}
Borrows {