diff --git a/compiler/rustc_mir_transform/src/coverage/spans.rs b/compiler/rustc_mir_transform/src/coverage/spans.rs index bb6a666ff73b1..84a70d1f02d75 100644 --- a/compiler/rustc_mir_transform/src/coverage/spans.rs +++ b/compiler/rustc_mir_transform/src/coverage/spans.rs @@ -1,9 +1,15 @@ +use std::collections::VecDeque; + +use rustc_data_structures::captures::Captures; +use rustc_data_structures::fx::FxHashSet; use rustc_middle::mir; use rustc_span::Span; use crate::coverage::graph::{BasicCoverageBlock, CoverageGraph}; use crate::coverage::mappings; -use crate::coverage::spans::from_mir::SpanFromMir; +use crate::coverage::spans::from_mir::{ + extract_covspans_and_holes_from_mir, ExtractedCovspans, Hole, SpanFromMir, +}; use crate::coverage::ExtractedHirInfo; mod from_mir; @@ -19,50 +25,181 @@ pub(super) fn extract_refined_covspans( basic_coverage_blocks: &CoverageGraph, code_mappings: &mut impl Extend, ) { - let sorted_span_buckets = - from_mir::mir_to_initial_sorted_coverage_spans(mir_body, hir_info, basic_coverage_blocks); - for bucket in sorted_span_buckets { - let refined_spans = refine_sorted_spans(bucket); - code_mappings.extend(refined_spans.into_iter().map(|RefinedCovspan { span, bcb }| { + let ExtractedCovspans { mut covspans, mut holes } = + extract_covspans_and_holes_from_mir(mir_body, hir_info, basic_coverage_blocks); + + // First, perform the passes that need macro information. + covspans.sort_by(|a, b| basic_coverage_blocks.cmp_in_dominator_order(a.bcb, b.bcb)); + remove_unwanted_macro_spans(&mut covspans); + split_visible_macro_spans(&mut covspans); + + // We no longer need the extra information in `SpanFromMir`, so convert to `Covspan`. + let mut covspans = covspans.into_iter().map(SpanFromMir::into_covspan).collect::>(); + + let compare_covspans = |a: &Covspan, b: &Covspan| { + 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()) + }; + covspans.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.) + covspans.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)); + + // Split the covspans into separate buckets that don't overlap any holes. + let buckets = divide_spans_into_buckets(covspans, &holes); + + for mut covspans in buckets { + // Make sure each individual bucket is internally sorted. + covspans.sort_by(compare_covspans); + let _span = debug_span!("processing bucket", ?covspans).entered(); + + let mut covspans = remove_unwanted_overlapping_spans(covspans); + debug!(?covspans, "after removing overlaps"); + + // Do one last merge pass, to simplify the output. + covspans.dedup_by(|b, a| a.merge_if_eligible(b)); + debug!(?covspans, "after merge"); + + code_mappings.extend(covspans.into_iter().map(|Covspan { span, bcb }| { // Each span produced by the refiner represents an ordinary code region. mappings::CodeMapping { span, bcb } })); } } -#[derive(Debug)] -struct RefinedCovspan { - span: Span, - bcb: BasicCoverageBlock, +/// Macros that expand into branches (e.g. `assert!`, `trace!`) tend to generate +/// multiple condition/consequent blocks that have the span of the whole macro +/// invocation, which is unhelpful. Keeping only the first such span seems to +/// give better mappings, so remove the others. +/// +/// (The input spans should be sorted in BCB dominator order, so that the +/// retained "first" span is likely to dominate the others.) +fn remove_unwanted_macro_spans(covspans: &mut Vec) { + let mut seen_macro_spans = FxHashSet::default(); + covspans.retain(|covspan| { + // Ignore (retain) non-macro-expansion spans. + if covspan.visible_macro.is_none() { + return true; + } + + // Retain only the first macro-expanded covspan with this span. + seen_macro_spans.insert(covspan.span) + }); } -impl RefinedCovspan { - fn is_mergeable(&self, other: &Self) -> bool { - self.bcb == other.bcb - } +/// When a span corresponds to a macro invocation that is visible from the +/// function body, split it into two parts. The first part covers just the +/// macro name plus `!`, and the second part covers the rest of the macro +/// invocation. This seems to give better results for code that uses macros. +fn split_visible_macro_spans(covspans: &mut Vec) { + let mut extra_spans = vec![]; - fn merge_from(&mut self, other: &Self) { - debug_assert!(self.is_mergeable(other)); - self.span = self.span.to(other.span); + covspans.retain(|covspan| { + let Some(visible_macro) = covspan.visible_macro else { return true }; + + let split_len = visible_macro.as_str().len() as u32 + 1; + let (before, after) = covspan.span.split_at(split_len); + if !covspan.span.contains(before) || !covspan.span.contains(after) { + // Something is unexpectedly wrong with the split point. + // The debug assertion in `split_at` will have already caught this, + // but in release builds it's safer to do nothing and maybe get a + // bug report for unexpected coverage, rather than risk an ICE. + return true; + } + + 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. + }); + + // The newly-split spans are added at the end, so any previous sorting + // is not preserved. + covspans.extend(extra_spans); +} + +/// Uses the holes to divide the given covspans into buckets, such that: +/// - No span in any hole overlaps a bucket (truncating the spans if necessary). +/// - The spans in each bucket are strictly after all spans in previous buckets, +/// and strictly before all spans in subsequent buckets. +/// +/// The resulting buckets are sorted relative to each other, but might not be +/// internally sorted. +#[instrument(level = "debug")] +fn divide_spans_into_buckets(input_covspans: Vec, holes: &[Hole]) -> Vec> { + debug_assert!(input_covspans.is_sorted_by(|a, b| compare_spans(a.span, b.span).is_le())); + debug_assert!(holes.is_sorted_by(|a, b| compare_spans(a.span, b.span).is_le())); + + // 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 input_covspans = VecDeque::from(input_covspans); + let mut fragments = 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::>(); + 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_input_covspans = + drain_front_while(&mut input_covspans, |c| c.span.lo() < hole.span.hi()); + + for covspan in fragments_from_prev.into_iter().chain(relevant_input_covspans) { + 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(input_covspans); + buckets.push(fragments); + + buckets +} + +/// 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, + mut pred_fn: impl FnMut(&T) -> bool, +) -> impl Iterator + Captures<'a> { + std::iter::from_fn(move || if pred_fn(queue.front()?) { queue.pop_front() } else { None }) } /// Takes one of the buckets of (sorted) spans extracted from MIR, and "refines" -/// those spans by removing spans that overlap in unwanted ways, and by merging -/// compatible adjacent spans. +/// those spans by removing spans that overlap in unwanted ways. #[instrument(level = "debug")] -fn refine_sorted_spans(sorted_spans: Vec) -> Vec { +fn remove_unwanted_overlapping_spans(sorted_spans: Vec) -> Vec { + debug_assert!(sorted_spans.is_sorted_by(|a, b| compare_spans(a.span, b.span).is_le())); + // Holds spans that have been read from the input vector, but haven't yet // been committed to the output vector. let mut pending = vec![]; let mut refined = vec![]; for curr in sorted_spans { - pending.retain(|prev: &SpanFromMir| { + pending.retain(|prev: &Covspan| { if prev.span.hi() <= curr.span.lo() { // There's no overlap between the previous/current covspans, // so move the previous one into the refined list. - refined.push(RefinedCovspan { span: prev.span, bcb: prev.bcb }); + refined.push(prev.clone()); false } else { // Otherwise, retain the previous covspan only if it has the @@ -75,22 +212,57 @@ fn refine_sorted_spans(sorted_spans: Vec) -> Vec { } // Drain the rest of the pending list into the refined list. - for prev in pending { - refined.push(RefinedCovspan { span: prev.span, bcb: prev.bcb }); + refined.extend(pending); + refined +} + +#[derive(Clone, Debug)] +struct Covspan { + span: Span, + bcb: BasicCoverageBlock, +} + +impl Covspan { + /// Splits this covspan 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, Option) { + 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) } - // Do one last merge pass, to simplify the output. - debug!(?refined, "before merge"); - refined.dedup_by(|b, a| { - if a.is_mergeable(b) { - debug!(?a, ?b, "merging list-adjacent refined spans"); - a.merge_from(b); - true - } else { - false + /// If `self` and `other` can be merged (i.e. they have the same BCB), + /// mutates `self.span` to also include `other.span` and returns true. + /// + /// Note that compatible covspans can be merged even if their underlying + /// spans are not overlapping/adjacent; any space between them will also be + /// part of the merged covspan. + fn merge_if_eligible(&mut self, other: &Self) -> bool { + if self.bcb != other.bcb { + return false; } - }); - debug!(?refined, "after merge"); - refined + self.span = self.span.to(other.span); + true + } +} + +/// Compares two spans in (lo ascending, hi descending) order. +fn compare_spans(a: Span, b: Span) -> std::cmp::Ordering { + // First sort by span start. + 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.hi(), &b.hi()).reverse()) } diff --git a/compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs b/compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs index b1f71035ddede..09deb7534bfde 100644 --- a/compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs +++ b/compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs @@ -1,7 +1,3 @@ -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; use rustc_middle::mir::{ @@ -13,25 +9,25 @@ use rustc_span::{ExpnKind, MacroKind, Span, Symbol}; use crate::coverage::graph::{ BasicCoverageBlock, BasicCoverageBlockData, CoverageGraph, START_BCB, }; +use crate::coverage::spans::Covspan; use crate::coverage::ExtractedHirInfo; +pub(crate) struct ExtractedCovspans { + pub(crate) covspans: Vec, + pub(crate) holes: Vec, +} + /// Traverses the MIR body to produce an initial collection of coverage-relevant /// spans, each associated with a node in the coverage graph (BCB) and possibly /// other metadata. -/// -/// 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( +pub(crate) fn extract_covspans_and_holes_from_mir( mir_body: &mir::Body<'_>, hir_info: &ExtractedHirInfo, basic_coverage_blocks: &CoverageGraph, -) -> Vec> { +) -> ExtractedCovspans { let &ExtractedHirInfo { body_span, .. } = hir_info; - let mut initial_spans = vec![]; + let mut covspans = vec![]; let mut holes = vec![]; for (bcb, bcb_data) in basic_coverage_blocks.iter_enumerated() { @@ -40,150 +36,21 @@ pub(super) fn mir_to_initial_sorted_coverage_spans( body_span, bcb, bcb_data, - &mut initial_spans, + &mut covspans, &mut holes, ); } // Only add the signature span if we found at least one span in the body. - if !initial_spans.is_empty() || !holes.is_empty() { + if !covspans.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. let fn_sig_span = hir_info.fn_sig_span_extended.unwrap_or_else(|| body_span.shrink_to_lo()); - initial_spans.push(SpanFromMir::for_fn_sig(fn_sig_span)); - } - - initial_spans.sort_by(|a, b| basic_coverage_blocks.cmp_in_dominator_order(a.bcb, b.bcb)); - remove_unwanted_macro_spans(&mut initial_spans); - split_visible_macro_spans(&mut initial_spans); - - 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 = 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::>(); - 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); - } + covspans.push(SpanFromMir::for_fn_sig(fn_sig_span)); } - // 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.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.hi(), &b.hi()).reverse()) -} - -/// 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, - mut pred_fn: impl FnMut(&T) -> bool, -) -> impl Iterator + 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 -/// multiple condition/consequent blocks that have the span of the whole macro -/// invocation, which is unhelpful. Keeping only the first such span seems to -/// give better mappings, so remove the others. -/// -/// (The input spans should be sorted in BCB dominator order, so that the -/// retained "first" span is likely to dominate the others.) -fn remove_unwanted_macro_spans(initial_spans: &mut Vec) { - let mut seen_macro_spans = FxHashSet::default(); - initial_spans.retain(|covspan| { - // Ignore (retain) non-macro-expansion spans. - if covspan.visible_macro.is_none() { - return true; - } - - // Retain only the first macro-expanded covspan with this span. - seen_macro_spans.insert(covspan.span) - }); -} - -/// When a span corresponds to a macro invocation that is visible from the -/// function body, split it into two parts. The first part covers just the -/// macro name plus `!`, and the second part covers the rest of the macro -/// invocation. This seems to give better results for code that uses macros. -fn split_visible_macro_spans(initial_spans: &mut Vec) { - let mut extra_spans = vec![]; - - initial_spans.retain(|covspan| { - let Some(visible_macro) = covspan.visible_macro else { return true }; - - let split_len = visible_macro.as_str().len() as u32 + 1; - let (before, after) = covspan.span.split_at(split_len); - if !covspan.span.contains(before) || !covspan.span.contains(after) { - // Something is unexpectedly wrong with the split point. - // The debug assertion in `split_at` will have already caught this, - // but in release builds it's safer to do nothing and maybe get a - // bug report for unexpected coverage, rather than risk an ICE. - return true; - } - - 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. - }); - - // The newly-split spans are added at the end, so any previous sorting - // is not preserved. - initial_spans.extend(extra_spans); + ExtractedCovspans { covspans, holes } } // Generate a set of coverage spans from the filtered set of `Statement`s and `Terminator`s of @@ -402,12 +269,12 @@ fn unexpand_into_body_span_with_prev( } #[derive(Debug)] -struct Hole { - span: Span, +pub(crate) struct Hole { + pub(crate) span: Span, } impl Hole { - fn merge_if_overlapping_or_adjacent(&mut self, other: &mut Self) -> bool { + pub(crate) fn merge_if_overlapping_or_adjacent(&mut self, other: &mut Self) -> bool { if !self.span.overlaps_or_adjacent(other.span) { return false; } @@ -418,7 +285,7 @@ impl Hole { } #[derive(Debug)] -pub(super) struct SpanFromMir { +pub(crate) struct SpanFromMir { /// A span that has been extracted from MIR and then "un-expanded" back to /// within the current function's `body_span`. After various intermediate /// processing steps, this span is emitted as part of the final coverage @@ -426,9 +293,9 @@ pub(super) struct SpanFromMir { /// /// With the exception of `fn_sig_span`, this should always be contained /// within `body_span`. - pub(super) span: Span, - visible_macro: Option, - pub(super) bcb: BasicCoverageBlock, + pub(crate) span: Span, + pub(crate) visible_macro: Option, + pub(crate) bcb: BasicCoverageBlock, } impl SpanFromMir { @@ -436,23 +303,12 @@ impl SpanFromMir { Self::new(fn_sig_span, None, START_BCB) } - fn new(span: Span, visible_macro: Option, bcb: BasicCoverageBlock) -> Self { + pub(crate) fn new(span: Span, visible_macro: Option, 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, Option) { - 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) + pub(crate) fn into_covspan(self) -> Covspan { + let Self { span, visible_macro: _, bcb } = self; + Covspan { span, bcb } } }