mikros/rust
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

coverage: Use hole spans to carve up coverage spans into separate buckets

Browse Source 
This performs the same task as the hole-carving code in the main span refiner,
but in a separate earlier pass.
This commit is contained in:
Zalathar 2024-06-03 17:15:50 +10:00
parent 464dee24ff
commit 6d1557f268
4 changed files with 152 additions and 65 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
compiler/rustc_mir_transform/src/coverage/spans.rs
View File

@ -262,7 +262,7 @@ fn next_coverage_span(&mut self) -> bool {
// a region of code, such as skipping past a hole.
debug!(?prev, "prev.span starts after curr.span, so curr will be dropped");
} else {
self.some_curr = Some(CurrCovspan::new(curr.span, curr.bcb, curr.is_hole));
self.some_curr = Some(CurrCovspan::new(curr.span, curr.bcb, false));
return true;
}
}

189
compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs
View File

@ -1,3 +1,6 @@
use std::collections::VecDeque;
use rustc_data_structures::captures::Captures;
use rustc_data_structures::fx::FxHashSet;
use rustc_middle::bug;
use rustc_middle::mir::coverage::CoverageKind;
@ -16,8 +19,11 @@
/// spans, each associated with a node in the coverage graph (BCB) and possibly
/// other metadata.
///
/// The returned spans are sorted in a specific order that is expected by the
/// subsequent span-refinement step.
/// The returned spans are divided into one or more buckets, such that:
/// - The spans in each bucket are strictly after all spans in previous buckets,
/// and strictly before all spans in subsequent buckets.
/// - The contents of each bucket are also sorted, in a specific order that is
/// expected by the subsequent span-refinement step.
pub(super) fn mir_to_initial_sorted_coverage_spans(
mir_body: &mir::Body<'_>,
hir_info: &ExtractedHirInfo,
@ -26,13 +32,21 @@ pub(super) fn mir_to_initial_sorted_coverage_spans(
let &ExtractedHirInfo { body_span, .. } = hir_info;
let mut initial_spans = vec![];
let mut holes = vec![];
for (bcb, bcb_data) in basic_coverage_blocks.iter_enumerated() {
bcb_to_initial_coverage_spans(mir_body, body_span, bcb, bcb_data, &mut initial_spans);
bcb_to_initial_coverage_spans(
mir_body,
body_span,
bcb,
bcb_data,
&mut initial_spans,
&mut holes,
);
}
// Only add the signature span if we found at least one span in the body.
if !initial_spans.is_empty() {
if !initial_spans.is_empty() || !holes.is_empty() {
// If there is no usable signature span, add a fake one (before refinement)
// to avoid an ugly gap between the body start and the first real span.
// FIXME: Find a more principled way to solve this problem.
@ -44,29 +58,82 @@ pub(super) fn mir_to_initial_sorted_coverage_spans(
remove_unwanted_macro_spans(&mut initial_spans);
split_visible_macro_spans(&mut initial_spans);
initial_spans.sort_by(|a, b| {
let compare_covspans = |a: &SpanFromMir, b: &SpanFromMir| {
compare_spans(a.span, b.span)
// After deduplication, we want to keep only the most-dominated BCB.
.then_with(|| basic_coverage_blocks.cmp_in_dominator_order(a.bcb, b.bcb).reverse())
};
initial_spans.sort_by(compare_covspans);
// Among covspans with the same span, keep only one,
// preferring the one with the most-dominated BCB.
// (Ideally we should try to preserve _all_ non-dominating BCBs, but that
// requires a lot more complexity in the span refiner, for little benefit.)
initial_spans.dedup_by(|b, a| a.span.source_equal(b.span));
// Sort the holes, and merge overlapping/adjacent holes.
holes.sort_by(|a, b| compare_spans(a.span, b.span));
holes.dedup_by(|b, a| a.merge_if_overlapping_or_adjacent(b));
// Now we're ready to start carving holes out of the initial coverage spans,
// and grouping them in buckets separated by the holes.
let mut initial_spans = VecDeque::from(initial_spans);
let mut fragments: Vec<SpanFromMir> = vec![];
// For each hole:
// - Identify the spans that are entirely or partly before the hole.
// - Put those spans in a corresponding bucket, truncated to the start of the hole.
// - If one of those spans also extends after the hole, put the rest of it
// in a "fragments" vector that is processed by the next hole.
let mut buckets = (0..holes.len()).map(|_| vec![]).collect::<Vec<_>>();
for (hole, bucket) in holes.iter().zip(&mut buckets) {
let fragments_from_prev = std::mem::take(&mut fragments);
// Only inspect spans that precede or overlap this hole,
// leaving the rest to be inspected by later holes.
// (This relies on the spans and holes both being sorted.)
let relevant_initial_spans =
drain_front_while(&mut initial_spans, |c| c.span.lo() < hole.span.hi());
for covspan in fragments_from_prev.into_iter().chain(relevant_initial_spans) {
let (before, after) = covspan.split_around_hole_span(hole.span);
bucket.extend(before);
fragments.extend(after);
}
}
// After finding the spans before each hole, any remaining fragments/spans
// form their own final bucket, after the final hole.
// (If there were no holes, this will just be all of the initial spans.)
fragments.extend(initial_spans);
buckets.push(fragments);
// Make sure each individual bucket is still internally sorted.
for bucket in &mut buckets {
bucket.sort_by(compare_covspans);
}
buckets
}
fn compare_spans(a: Span, b: Span) -> std::cmp::Ordering {
// First sort by span start.
Ord::cmp(&a.span.lo(), &b.span.lo())
Ord::cmp(&a.lo(), &b.lo())
// If span starts are the same, sort by span end in reverse order.
// This ensures that if spans A and B are adjacent in the list,
// and they overlap but are not equal, then either:
// - Span A extends further left, or
// - Both have the same start and span A extends further right
.then_with(|| Ord::cmp(&a.span.hi(), &b.span.hi()).reverse())
// If two spans have the same lo & hi, put hole spans first,
// as they take precedence over non-hole spans.
.then_with(|| Ord::cmp(&a.is_hole, &b.is_hole).reverse())
// After deduplication, we want to keep only the most-dominated BCB.
.then_with(|| basic_coverage_blocks.cmp_in_dominator_order(a.bcb, b.bcb).reverse())
});
.then_with(|| Ord::cmp(&a.hi(), &b.hi()).reverse())
}
// Among covspans with the same span, keep only one. Hole spans take
// precedence, otherwise keep the one with the most-dominated BCB.
// (Ideally we should try to preserve _all_ non-dominating BCBs, but that
// requires a lot more complexity in the span refiner, for little benefit.)
initial_spans.dedup_by(|b, a| a.span.source_equal(b.span));
vec![initial_spans]
/// Similar to `.drain(..)`, but stops just before it would remove an item not
/// satisfying the predicate.
fn drain_front_while<'a, T>(
queue: &'a mut VecDeque<T>,
mut pred_fn: impl FnMut(&T) -> bool,
) -> impl Iterator<Item = T> + Captures<'a> {
std::iter::from_fn(move || if pred_fn(queue.front()?) { queue.pop_front() } else { None })
}
/// Macros that expand into branches (e.g. `assert!`, `trace!`) tend to generate
@ -79,8 +146,8 @@ pub(super) fn mir_to_initial_sorted_coverage_spans(
fn remove_unwanted_macro_spans(initial_spans: &mut Vec<SpanFromMir>) {
let mut seen_macro_spans = FxHashSet::default();
initial_spans.retain(|covspan| {
// Ignore (retain) hole spans and non-macro-expansion spans.
if covspan.is_hole || covspan.visible_macro.is_none() {
// Ignore (retain) non-macro-expansion spans.
if covspan.visible_macro.is_none() {
return true;
}
@ -97,10 +164,6 @@ fn split_visible_macro_spans(initial_spans: &mut Vec<SpanFromMir>) {
let mut extra_spans = vec![];
initial_spans.retain(|covspan| {
if covspan.is_hole {
return true;
}
let Some(visible_macro) = covspan.visible_macro else { return true };
let split_len = visible_macro.as_str().len() as u32 + 1;
@ -113,9 +176,8 @@ fn split_visible_macro_spans(initial_spans: &mut Vec<SpanFromMir>) {
return true;
}
assert!(!covspan.is_hole);
extra_spans.push(SpanFromMir::new(before, covspan.visible_macro, covspan.bcb, false));
extra_spans.push(SpanFromMir::new(after, covspan.visible_macro, covspan.bcb, false));
extra_spans.push(SpanFromMir::new(before, covspan.visible_macro, covspan.bcb));
extra_spans.push(SpanFromMir::new(after, covspan.visible_macro, covspan.bcb));
false // Discard the original covspan that we just split.
});
@ -135,6 +197,7 @@ fn bcb_to_initial_coverage_spans<'a, 'tcx>(
bcb: BasicCoverageBlock,
bcb_data: &'a BasicCoverageBlockData,
initial_covspans: &mut Vec<SpanFromMir>,
holes: &mut Vec<Hole>,
) {
for &bb in &bcb_data.basic_blocks {
let data = &mir_body[bb];
@ -146,26 +209,31 @@ fn bcb_to_initial_coverage_spans<'a, 'tcx>(
.filter(|(span, _)| !span.source_equal(body_span))
};
for statement in data.statements.iter() {
let _: Option<()> = try {
let mut extract_statement_span = |statement| {
let expn_span = filtered_statement_span(statement)?;
let (span, visible_macro) = unexpand(expn_span)?;
// A statement that looks like the assignment of a closure expression
// is treated as a "hole" span, to be carved out of other spans.
let covspan =
SpanFromMir::new(span, visible_macro, bcb, is_closure_like(statement));
initial_covspans.push(covspan);
if is_closure_like(statement) {
holes.push(Hole { span });
} else {
initial_covspans.push(SpanFromMir::new(span, visible_macro, bcb));
}
Some(())
};
for statement in data.statements.iter() {
extract_statement_span(statement);
}
let _: Option<()> = try {
let terminator = data.terminator();
let mut extract_terminator_span = |terminator| {
let expn_span = filtered_terminator_span(terminator)?;
let (span, visible_macro) = unexpand(expn_span)?;
initial_covspans.push(SpanFromMir::new(span, visible_macro, bcb, false));
initial_covspans.push(SpanFromMir::new(span, visible_macro, bcb));
Some(())
};
extract_terminator_span(data.terminator());
}
}
@ -333,6 +401,22 @@ fn unexpand_into_body_span_with_prev(
Some((curr, prev))
}
#[derive(Debug)]
struct Hole {
span: Span,
}
impl Hole {
fn merge_if_overlapping_or_adjacent(&mut self, other: &mut Self) -> bool {
if !self.span.overlaps_or_adjacent(other.span) {
return false;
}
self.span = self.span.to(other.span);
true
}
}
#[derive(Debug)]
pub(super) struct SpanFromMir {
/// A span that has been extracted from MIR and then "un-expanded" back to
@ -345,23 +429,30 @@ pub(super) struct SpanFromMir {
pub(super) span: Span,
visible_macro: Option<Symbol>,
pub(super) bcb: BasicCoverageBlock,
/// If true, this covspan represents a "hole" that should be carved out
/// from other spans, e.g. because it represents a closure expression that
/// will be instrumented separately as its own function.
pub(super) is_hole: bool,
}
impl SpanFromMir {
fn for_fn_sig(fn_sig_span: Span) -> Self {
Self::new(fn_sig_span, None, START_BCB, false)
Self::new(fn_sig_span, None, START_BCB)
}
fn new(
span: Span,
visible_macro: Option<Symbol>,
bcb: BasicCoverageBlock,
is_hole: bool,
) -> Self {
Self { span, visible_macro, bcb, is_hole }
fn new(span: Span, visible_macro: Option<Symbol>, bcb: BasicCoverageBlock) -> Self {
Self { span, visible_macro, bcb }
}
/// Splits this span into 0-2 parts:
/// - The part that is strictly before the hole span, if any.
/// - The part that is strictly after the hole span, if any.
fn split_around_hole_span(&self, hole_span: Span) -> (Option<Self>, Option<Self>) {
let before = try {
let span = self.span.trim_end(hole_span)?;
Self { span, ..*self }
};
let after = try {
let span = self.span.trim_start(hole_span)?;
Self { span, ..*self }
};
(before, after)
}
}

8
tests/coverage/closure_macro.cov-map
View File

@ -7,16 +7,14 @@ Number of file 0 mappings: 1
- Code(Counter(0)) at (prev + 29, 1) to (start + 2, 2)
Function name: closure_macro::main
Raw bytes (36): 0x[01, 01, 01, 01, 05, 06, 01, 21, 01, 01, 21, 02, 02, 09, 00, 12, 02, 00, 0f, 00, 54, 05, 00, 54, 00, 55, 02, 02, 09, 02, 0b, 01, 03, 01, 00, 02]
Raw bytes (31): 0x[01, 01, 01, 01, 05, 05, 01, 21, 01, 01, 21, 02, 02, 09, 00, 0f, 05, 00, 54, 00, 55, 02, 02, 09, 02, 0b, 01, 03, 01, 00, 02]
Number of files: 1
- file 0 => global file 1
Number of expressions: 1
- expression 0 operands: lhs = Counter(0), rhs = Counter(1)
Number of file 0 mappings: 6
Number of file 0 mappings: 5
- Code(Counter(0)) at (prev + 33, 1) to (start + 1, 33)
- Code(Expression(0, Sub)) at (prev + 2, 9) to (start + 0, 18)
= (c0 - c1)
- Code(Expression(0, Sub)) at (prev + 0, 15) to (start + 0, 84)
- Code(Expression(0, Sub)) at (prev + 2, 9) to (start + 0, 15)
= (c0 - c1)
- Code(Counter(1)) at (prev + 0, 84) to (start + 0, 85)
- Code(Expression(0, Sub)) at (prev + 2, 9) to (start + 2, 11)

8
tests/coverage/closure_macro_async.cov-map
View File

@ -15,16 +15,14 @@ Number of file 0 mappings: 1
- Code(Counter(0)) at (prev + 35, 1) to (start + 0, 43)
Function name: closure_macro_async::test::{closure#0}
Raw bytes (36): 0x[01, 01, 01, 01, 05, 06, 01, 23, 2b, 01, 21, 02, 02, 09, 00, 12, 02, 00, 0f, 00, 54, 05, 00, 54, 00, 55, 02, 02, 09, 02, 0b, 01, 03, 01, 00, 02]
Raw bytes (31): 0x[01, 01, 01, 01, 05, 05, 01, 23, 2b, 01, 21, 02, 02, 09, 00, 0f, 05, 00, 54, 00, 55, 02, 02, 09, 02, 0b, 01, 03, 01, 00, 02]
Number of files: 1
- file 0 => global file 1
Number of expressions: 1
- expression 0 operands: lhs = Counter(0), rhs = Counter(1)
Number of file 0 mappings: 6
Number of file 0 mappings: 5
- Code(Counter(0)) at (prev + 35, 43) to (start + 1, 33)
- Code(Expression(0, Sub)) at (prev + 2, 9) to (start + 0, 18)
= (c0 - c1)
- Code(Expression(0, Sub)) at (prev + 0, 15) to (start + 0, 84)
- Code(Expression(0, Sub)) at (prev + 2, 9) to (start + 0, 15)
= (c0 - c1)
- Code(Counter(1)) at (prev + 0, 84) to (start + 0, 85)
- Code(Expression(0, Sub)) at (prev + 2, 9) to (start + 2, 11)