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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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8
compiler/rustc_middle/src/mir/coverage.rs
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@ -76,6 +76,13 @@ impl Debug for CovTerm {
#[derive(Clone, PartialEq, TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable, TypeVisitable)]
pub enum CoverageKind {
/// Marks a span that might otherwise not be represented in MIR, so that
/// coverage instrumentation can associate it with its enclosing block/BCB.
///
/// Only used by the `InstrumentCoverage` pass, and has no effect during
/// codegen.
SpanMarker,
/// Marks the point in MIR control flow represented by a coverage counter.
///
/// This is eventually lowered to `llvm.instrprof.increment` in LLVM IR.
@ -99,6 +106,7 @@ impl Debug for CoverageKind {
fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
use CoverageKind::*;
match self {
SpanMarker => write!(fmt, "SpanMarker"),
CounterIncrement { id } => write!(fmt, "CounterIncrement({:?})", id.index()),
ExpressionUsed { id } => write!(fmt, "ExpressionUsed({:?})", id.index()),
}