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coverage: Avoid a possible query stability hazard in CoverageCounters

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The iteration order of this hashmap can potentially affect the relative
creation order of MIR blocks.
This commit is contained in:
Zalathar 2023-12-29 12:00:48 +11:00
parent fb5ed726f7
commit 8529b63e2b
1 changed files with 6 additions and 3 deletions
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9
compiler/rustc_mir_transform/src/coverage/counters.rs
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@ -1,4 +1,4 @@
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::fx::FxIndexMap;
use rustc_data_structures::graph::WithNumNodes;
use rustc_index::bit_set::BitSet;
use rustc_index::IndexVec;
@ -47,7 +47,10 @@ pub(super) struct CoverageCounters {
bcb_counters: IndexVec<BasicCoverageBlock, Option<BcbCounter>>,
/// Coverage counters/expressions that are associated with the control-flow
/// edge between two BCBs.
bcb_edge_counters: FxHashMap<(BasicCoverageBlock, BasicCoverageBlock), BcbCounter>,
///
/// The iteration order of this map can affect the precise contents of MIR,
/// so we use `FxIndexMap` to avoid query stability hazards.
bcb_edge_counters: FxIndexMap<(BasicCoverageBlock, BasicCoverageBlock), BcbCounter>,
/// Tracks which BCBs have a counter associated with some incoming edge.
/// Only used by assertions, to verify that BCBs with incoming edge
/// counters do not have their own physical counters (expressions are allowed).
@ -64,7 +67,7 @@ impl CoverageCounters {
Self {
next_counter_id: CounterId::START,
bcb_counters: IndexVec::from_elem_n(None, num_bcbs),
bcb_edge_counters: FxHashMap::default(),
bcb_edge_counters: FxIndexMap::default(),
bcb_has_incoming_edge_counters: BitSet::new_empty(num_bcbs),
expressions: IndexVec::new(),
}