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coverage: Simplify the coverageinfo query to a single pass

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This commit is contained in:
Zalathar 2023-08-30 23:36:11 +10:00
parent 3f549466a8
commit f191b1c2fc
1 changed files with 13 additions and 30 deletions
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43
compiler/rustc_mir_transform/src/coverage/query.rs
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@ -29,18 +29,12 @@ pub(crate) fn provide(providers: &mut Providers) {
/// calls may not work; but computing the number of counters or expressions by adding `1` to the
/// highest ID (for a given instrumented function) is valid.
///
/// This visitor runs twice, first with `add_missing_operands` set to `false`, to find the maximum
/// counter ID and maximum expression ID based on their enum variant `id` fields; then, as a
/// safeguard, with `add_missing_operands` set to `true`, to find any other counter or expression
/// IDs referenced by expression operands, if not already seen.
///
/// Ideally, each operand ID in a MIR `CoverageKind::Expression` will have a separate MIR `Coverage`
/// statement for the `Counter` or `Expression` with the referenced ID. but since current or future
/// MIR optimizations can theoretically optimize out segments of a MIR, it may not be possible to
/// guarantee this, so the second pass ensures the `CoverageInfo` counts include all referenced IDs.
/// It's possible for a coverage expression to remain in MIR while one or both of its operands
/// have been optimized away. To avoid problems in codegen, we include those operands' IDs when
/// determining the maximum counter/expression ID, even if the underlying counter/expression is
/// no longer present.
struct CoverageVisitor {
info: CoverageInfo,
add_missing_operands: bool,
}
impl CoverageVisitor {
@ -73,20 +67,14 @@ impl CoverageVisitor {
}
fn visit_coverage(&mut self, coverage: &Coverage) {
if self.add_missing_operands {
match coverage.kind {
CoverageKind::Expression { lhs, rhs, .. } => {
self.update_from_expression_operand(lhs);
self.update_from_expression_operand(rhs);
}
_ => {}
}
} else {
match coverage.kind {
CoverageKind::Counter { id, .. } => self.update_num_counters(id),
CoverageKind::Expression { id, .. } => self.update_num_expressions(id),
_ => {}
match coverage.kind {
CoverageKind::Counter { id, .. } => self.update_num_counters(id),
CoverageKind::Expression { id, lhs, rhs, .. } => {
self.update_num_expressions(id);
self.update_from_expression_operand(lhs);
self.update_from_expression_operand(rhs);
}
CoverageKind::Unreachable => {}
}
}
}
@ -94,16 +82,11 @@ impl CoverageVisitor {
fn coverageinfo<'tcx>(tcx: TyCtxt<'tcx>, instance_def: ty::InstanceDef<'tcx>) -> CoverageInfo {
let mir_body = tcx.instance_mir(instance_def);
let mut coverage_visitor = CoverageVisitor {
info: CoverageInfo { num_counters: 0, num_expressions: 0 },
add_missing_operands: false,
};
let mut coverage_visitor =
CoverageVisitor { info: CoverageInfo { num_counters: 0, num_expressions: 0 } };
coverage_visitor.visit_body(mir_body);
coverage_visitor.add_missing_operands = true;
coverage_visitor.visit_body(mir_body);
coverage_visitor.info
}