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coverage: Dismantle Instrumentor and flatten span refinement #120292

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Jan 25, 2024
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coverage: Dismantle Instrumentor and flatten span refinement #120292

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83ef18c
coverage: Dismantle `Instrumentor` into ordinary functions
Zalathar Jan 24, 2024
572d7e9
coverage: Flatten the functions for extracting/refining coverage spans
Zalathar Jan 24, 2024
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265 changes: 126 additions & 139 deletions compiler/rustc_mir_transform/src/coverage/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -59,167 +59,154 @@ impl<'tcx> MirPass<'tcx> for InstrumentCoverage {
_ => {}
}

trace!("InstrumentCoverage starting for {def_id:?}");
Instrumentor::new(tcx, mir_body).inject_counters();
trace!("InstrumentCoverage done for {def_id:?}");
instrument_function_for_coverage(tcx, mir_body);
}
}

struct Instrumentor<'a, 'tcx> {
tcx: TyCtxt<'tcx>,
mir_body: &'a mut mir::Body<'tcx>,
hir_info: ExtractedHirInfo,
basic_coverage_blocks: CoverageGraph,
}

impl<'a, 'tcx> Instrumentor<'a, 'tcx> {
fn new(tcx: TyCtxt<'tcx>, mir_body: &'a mut mir::Body<'tcx>) -> Self {
let hir_info = extract_hir_info(tcx, mir_body.source.def_id().expect_local());
fn instrument_function_for_coverage<'tcx>(tcx: TyCtxt<'tcx>, mir_body: &mut mir::Body<'tcx>) {
let def_id = mir_body.source.def_id();
let _span = debug_span!("instrument_function_for_coverage", ?def_id).entered();

debug!(?hir_info, "instrumenting {:?}", mir_body.source.def_id());
let hir_info = extract_hir_info(tcx, def_id.expect_local());
let basic_coverage_blocks = CoverageGraph::from_mir(mir_body);

let basic_coverage_blocks = CoverageGraph::from_mir(mir_body);
////////////////////////////////////////////////////
// Compute coverage spans from the `CoverageGraph`.
let Some(coverage_spans) =
spans::generate_coverage_spans(mir_body, &hir_info, &basic_coverage_blocks)
else {
// No relevant spans were found in MIR, so skip instrumenting this function.
return;
};

Self { tcx, mir_body, hir_info, basic_coverage_blocks }
////////////////////////////////////////////////////
// Create an optimized mix of `Counter`s and `Expression`s for the `CoverageGraph`. Ensure
// every coverage span has a `Counter` or `Expression` assigned to its `BasicCoverageBlock`
// and all `Expression` dependencies (operands) are also generated, for any other
// `BasicCoverageBlock`s not already associated with a coverage span.
let bcb_has_coverage_spans = |bcb| coverage_spans.bcb_has_coverage_spans(bcb);
let coverage_counters =
CoverageCounters::make_bcb_counters(&basic_coverage_blocks, bcb_has_coverage_spans);

let mappings = create_mappings(tcx, &hir_info, &coverage_spans, &coverage_counters);
if mappings.is_empty() {
// No spans could be converted into valid mappings, so skip this function.
debug!("no spans could be converted into valid mappings; skipping");
return;
}

fn inject_counters(&'a mut self) {
////////////////////////////////////////////////////
// Compute coverage spans from the `CoverageGraph`.
let Some(coverage_spans) = CoverageSpans::generate_coverage_spans(
self.mir_body,
&self.hir_info,
&self.basic_coverage_blocks,
) else {
// No relevant spans were found in MIR, so skip instrumenting this function.
return;
};

////////////////////////////////////////////////////
// Create an optimized mix of `Counter`s and `Expression`s for the `CoverageGraph`. Ensure
// every coverage span has a `Counter` or `Expression` assigned to its `BasicCoverageBlock`
// and all `Expression` dependencies (operands) are also generated, for any other
// `BasicCoverageBlock`s not already associated with a coverage span.
let bcb_has_coverage_spans = |bcb| coverage_spans.bcb_has_coverage_spans(bcb);
let coverage_counters = CoverageCounters::make_bcb_counters(
&self.basic_coverage_blocks,
bcb_has_coverage_spans,
);
inject_coverage_statements(
mir_body,
&basic_coverage_blocks,
bcb_has_coverage_spans,
&coverage_counters,
);

let mappings = self.create_mappings(&coverage_spans, &coverage_counters);
if mappings.is_empty() {
// No spans could be converted into valid mappings, so skip this function.
debug!("no spans could be converted into valid mappings; skipping");
return;
}
mir_body.function_coverage_info = Some(Box::new(FunctionCoverageInfo {
function_source_hash: hir_info.function_source_hash,
num_counters: coverage_counters.num_counters(),
expressions: coverage_counters.into_expressions(),
mappings,
}));
}

self.inject_coverage_statements(bcb_has_coverage_spans, &coverage_counters);
/// For each coverage span extracted from MIR, create a corresponding
/// mapping.
///
/// Precondition: All BCBs corresponding to those spans have been given
/// coverage counters.
fn create_mappings<'tcx>(
tcx: TyCtxt<'tcx>,
hir_info: &ExtractedHirInfo,
coverage_spans: &CoverageSpans,
coverage_counters: &CoverageCounters,
) -> Vec<Mapping> {
let source_map = tcx.sess.source_map();
let body_span = hir_info.body_span;

let source_file = source_map.lookup_source_file(body_span.lo());
use rustc_session::RemapFileNameExt;
let file_name = Symbol::intern(&source_file.name.for_codegen(tcx.sess).to_string_lossy());

let term_for_bcb = |bcb| {
coverage_counters
.bcb_counter(bcb)
.expect("all BCBs with spans were given counters")
.as_term()
};

self.mir_body.function_coverage_info = Some(Box::new(FunctionCoverageInfo {
function_source_hash: self.hir_info.function_source_hash,
num_counters: coverage_counters.num_counters(),
expressions: coverage_counters.into_expressions(),
mappings,
}));
}
coverage_spans
.all_bcb_mappings()
.filter_map(|&BcbMapping { kind: bcb_mapping_kind, span }| {
let kind = match bcb_mapping_kind {
BcbMappingKind::Code(bcb) => MappingKind::Code(term_for_bcb(bcb)),
};
let code_region = make_code_region(source_map, file_name, span, body_span)?;
Some(Mapping { kind, code_region })
})
.collect::<Vec<_>>()
}

/// For each coverage span extracted from MIR, create a corresponding
/// mapping.
///
/// Precondition: All BCBs corresponding to those spans have been given
/// coverage counters.
fn create_mappings(
&self,
coverage_spans: &CoverageSpans,
coverage_counters: &CoverageCounters,
) -> Vec<Mapping> {
let source_map = self.tcx.sess.source_map();
let body_span = self.hir_info.body_span;

let source_file = source_map.lookup_source_file(body_span.lo());
use rustc_session::RemapFileNameExt;
let file_name =
Symbol::intern(&source_file.name.for_codegen(self.tcx.sess).to_string_lossy());

let term_for_bcb = |bcb| {
coverage_counters
.bcb_counter(bcb)
.expect("all BCBs with spans were given counters")
.as_term()
/// For each BCB node or BCB edge that has an associated coverage counter,
/// inject any necessary coverage statements into MIR.
fn inject_coverage_statements<'tcx>(
mir_body: &mut mir::Body<'tcx>,
basic_coverage_blocks: &CoverageGraph,
bcb_has_coverage_spans: impl Fn(BasicCoverageBlock) -> bool,
coverage_counters: &CoverageCounters,
) {
// Process the counters associated with BCB nodes.
for (bcb, counter_kind) in coverage_counters.bcb_node_counters() {
let do_inject = match counter_kind {
// Counter-increment statements always need to be injected.
BcbCounter::Counter { .. } => true,
// The only purpose of expression-used statements is to detect
// when a mapping is unreachable, so we only inject them for
// expressions with one or more mappings.
BcbCounter::Expression { .. } => bcb_has_coverage_spans(bcb),
};

coverage_spans
.all_bcb_mappings()
.filter_map(|&BcbMapping { kind: bcb_mapping_kind, span }| {
let kind = match bcb_mapping_kind {
BcbMappingKind::Code(bcb) => MappingKind::Code(term_for_bcb(bcb)),
};
let code_region = make_code_region(source_map, file_name, span, body_span)?;
Some(Mapping { kind, code_region })
})
.collect::<Vec<_>>()
if do_inject {
inject_statement(
mir_body,
make_mir_coverage_kind(counter_kind),
basic_coverage_blocks[bcb].leader_bb(),
);
}
}

/// For each BCB node or BCB edge that has an associated coverage counter,
/// inject any necessary coverage statements into MIR.
fn inject_coverage_statements(
&mut self,
bcb_has_coverage_spans: impl Fn(BasicCoverageBlock) -> bool,
coverage_counters: &CoverageCounters,
) {
// Process the counters associated with BCB nodes.
for (bcb, counter_kind) in coverage_counters.bcb_node_counters() {
let do_inject = match counter_kind {
// Counter-increment statements always need to be injected.
BcbCounter::Counter { .. } => true,
// The only purpose of expression-used statements is to detect
// when a mapping is unreachable, so we only inject them for
// expressions with one or more mappings.
BcbCounter::Expression { .. } => bcb_has_coverage_spans(bcb),
};
if do_inject {
inject_statement(
self.mir_body,
self.make_mir_coverage_kind(counter_kind),
self.basic_coverage_blocks[bcb].leader_bb(),
);
}
// Process the counters associated with BCB edges.
for (from_bcb, to_bcb, counter_kind) in coverage_counters.bcb_edge_counters() {
let do_inject = match counter_kind {
// Counter-increment statements always need to be injected.
BcbCounter::Counter { .. } => true,
// BCB-edge expressions never have mappings, so they never need
// a corresponding statement.
BcbCounter::Expression { .. } => false,
};
if !do_inject {
continue;
}

// Process the counters associated with BCB edges.
for (from_bcb, to_bcb, counter_kind) in coverage_counters.bcb_edge_counters() {
let do_inject = match counter_kind {
// Counter-increment statements always need to be injected.
BcbCounter::Counter { .. } => true,
// BCB-edge expressions never have mappings, so they never need
// a corresponding statement.
BcbCounter::Expression { .. } => false,
};
if !do_inject {
continue;
}
// We need to inject a coverage statement into a new BB between the
// last BB of `from_bcb` and the first BB of `to_bcb`.
let from_bb = basic_coverage_blocks[from_bcb].last_bb();
let to_bb = basic_coverage_blocks[to_bcb].leader_bb();

// We need to inject a coverage statement into a new BB between the
// last BB of `from_bcb` and the first BB of `to_bcb`.
let from_bb = self.basic_coverage_blocks[from_bcb].last_bb();
let to_bb = self.basic_coverage_blocks[to_bcb].leader_bb();

let new_bb = inject_edge_counter_basic_block(self.mir_body, from_bb, to_bb);
debug!(
"Edge {from_bcb:?} (last {from_bb:?}) -> {to_bcb:?} (leader {to_bb:?}) \
let new_bb = inject_edge_counter_basic_block(mir_body, from_bb, to_bb);
debug!(
"Edge {from_bcb:?} (last {from_bb:?}) -> {to_bcb:?} (leader {to_bb:?}) \
requires a new MIR BasicBlock {new_bb:?} for edge counter {counter_kind:?}",
);
);

// Inject a counter into the newly-created BB.
inject_statement(self.mir_body, self.make_mir_coverage_kind(counter_kind), new_bb);
}
// Inject a counter into the newly-created BB.
inject_statement(mir_body, make_mir_coverage_kind(counter_kind), new_bb);
}
}

fn make_mir_coverage_kind(&self, counter_kind: &BcbCounter) -> CoverageKind {
match *counter_kind {
BcbCounter::Counter { id } => CoverageKind::CounterIncrement { id },
BcbCounter::Expression { id } => CoverageKind::ExpressionUsed { id },
}
fn make_mir_coverage_kind(counter_kind: &BcbCounter) -> CoverageKind {
match *counter_kind {
BcbCounter::Counter { id } => CoverageKind::CounterIncrement { id },
BcbCounter::Expression { id } => CoverageKind::ExpressionUsed { id },
}
}

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