bjoernager/rust
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coverage: Add CoverageKind::SpanMarker for including extra spans in MIR

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There are cases where coverage instrumentation wants to show a span for some
syntax element, but there is no MIR node that naturally carries that span, so
the instrumentor can't see it.

MIR building can now use this new kind of coverage statement to deliberately
include those spans in MIR, attached to a dummy statement that has no other
effect.
This commit is contained in:
Zalathar 2023-11-23 11:50:39 +11:00
parent d2d742c4cc
commit 44b47aa976
4 changed files with 36 additions and 3 deletions
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15
compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs
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@ -92,13 +92,13 @@ fn is_closure(statement: &Statement<'_>) -> bool {
/// If the MIR `Statement` has a span contributive to computing coverage spans,
/// return it; otherwise return `None`.
fn filtered_statement_span(statement: &Statement<'_>) -> Option<Span> {
use mir::coverage::CoverageKind;
match statement.kind {
// These statements have spans that are often outside the scope of the executed source code
// for their parent `BasicBlock`.
StatementKind::StorageLive(_)
| StatementKind::StorageDead(_)
// Coverage should not be encountered, but don't inject coverage coverage
| StatementKind::Coverage(_)
// Ignore `ConstEvalCounter`s
| StatementKind::ConstEvalCounter
// Ignore `Nop`s
@ -122,9 +122,13 @@ fn filtered_statement_span(statement: &Statement<'_>) -> Option<Span> {
// If and when the Issue is resolved, remove this special case match pattern:
StatementKind::FakeRead(box (FakeReadCause::ForGuardBinding, _)) => None,
// Retain spans from all other statements
// Retain spans from most other statements.
StatementKind::FakeRead(box (_, _)) // Not including `ForGuardBinding`
| StatementKind::Intrinsic(..)
| StatementKind::Coverage(box mir::Coverage {
// The purpose of `SpanMarker` is to be matched and accepted here.
kind: CoverageKind::SpanMarker
})
| StatementKind::Assign(_)
| StatementKind::SetDiscriminant { .. }
| StatementKind::Deinit(..)
@ -133,6 +137,11 @@ fn filtered_statement_span(statement: &Statement<'_>) -> Option<Span> {
| StatementKind::AscribeUserType(_, _) => {
Some(statement.source_info.span)
}
StatementKind::Coverage(box mir::Coverage {
// These coverage statements should not exist prior to coverage instrumentation.
kind: CoverageKind::CounterIncrement { .. } | CoverageKind::ExpressionUsed { .. }
}) => bug!("Unexpected coverage statement found during coverage instrumentation: {statement:?}"),
}
}