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coverage: Hoist the removal of unwanted macro expansion spans

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This commit is contained in:
Zalathar 2023-12-21 23:03:45 +11:00
parent df0df5256b
commit cd3a9760e4
2 changed files with 27 additions and 26 deletions
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24
compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs
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@ -1,4 +1,5 @@
use rustc_data_structures::captures::Captures;
use rustc_data_structures::fx::FxHashSet;
use rustc_middle::mir::{
self, AggregateKind, FakeReadCause, Rvalue, Statement, StatementKind, Terminator,
TerminatorKind,
@ -35,6 +36,9 @@ pub(super) fn mir_to_initial_sorted_coverage_spans(
}
}
initial_spans.sort_by(|a, b| basic_coverage_blocks.cmp_in_dominator_order(a.bcb, b.bcb));
remove_unwanted_macro_spans(&mut initial_spans);
initial_spans.sort_by(|a, b| {
// First sort by span start.
Ord::cmp(&a.span.lo(), &b.span.lo())
@ -55,6 +59,26 @@ pub(super) fn mir_to_initial_sorted_coverage_spans(
initial_spans
}
/// Macros that expand into branches (e.g. `assert!`, `trace!`) tend to generate
/// multiple condition/consequent blocks that have the span of the whole macro
/// invocation, which is unhelpful. Keeping only the first such span seems to
/// give better mappings, so remove the others.
///
/// (The input spans should be sorted in BCB dominator order, so that the
/// retained "first" span is likely to dominate the others.)
fn remove_unwanted_macro_spans(initial_spans: &mut Vec<CoverageSpan>) {
let mut seen_macro_spans = FxHashSet::default();
initial_spans.retain(|covspan| {
// Ignore (retain) closure spans and non-macro-expansion spans.
if covspan.is_closure || covspan.visible_macro.is_none() {
return true;
}
// Retain only the first macro-expanded covspan with this span.
seen_macro_spans.insert(covspan.span)
});
}
// Generate a set of `CoverageSpan`s from the filtered set of `Statement`s and `Terminator`s of
// the `BasicBlock`(s) in the given `BasicCoverageBlockData`. One `CoverageSpan` is generated
// for each `Statement` and `Terminator`. (Note that subsequent stages of coverage analysis will