From f877aa7d14916f71a2f88c6d4c009e7ded7684c4 Mon Sep 17 00:00:00 2001 From: Zalathar Date: Sun, 4 May 2025 14:09:52 +1000 Subject: [PATCH] coverage: Enlarge empty spans during MIR instrumentation, not codegen This allows us to assume that coverage spans will only be discarded during codegen in very unusual situations. --- .../src/coverageinfo/mapgen/spans.rs | 28 ++------------ .../rustc_mir_transform/src/coverage/spans.rs | 38 ++++++++++++++++++- tests/coverage/async_closure.cov-map | 21 +++++----- ...ch_match_arms.main.InstrumentCoverage.diff | 2 +- ...ument_coverage.bar.InstrumentCoverage.diff | 2 +- ...ment_coverage.main.InstrumentCoverage.diff | 4 +- ...rage_cleanup.main.CleanupPostBorrowck.diff | 4 +- ...erage_cleanup.main.InstrumentCoverage.diff | 4 +- 8 files changed, 57 insertions(+), 46 deletions(-) diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/spans.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/spans.rs index 39a59560c9d3e..574463be7ffe0 100644 --- a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/spans.rs +++ b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/spans.rs @@ -39,7 +39,10 @@ impl Coords { /// or other expansions), and if it does happen then skipping a span or function is /// better than an ICE or `llvm-cov` failure that the user might have no way to avoid. pub(crate) fn make_coords(source_map: &SourceMap, file: &SourceFile, span: Span) -> Option { - let span = ensure_non_empty_span(source_map, span)?; + if span.is_empty() { + debug_assert!(false, "can't make coords from empty span: {span:?}"); + return None; + } let lo = span.lo(); let hi = span.hi(); @@ -70,29 +73,6 @@ pub(crate) fn make_coords(source_map: &SourceMap, file: &SourceFile, span: Span) }) } -fn ensure_non_empty_span(source_map: &SourceMap, span: Span) -> Option { - if !span.is_empty() { - return Some(span); - } - - // The span is empty, so try to enlarge it to cover an adjacent '{' or '}'. - source_map - .span_to_source(span, |src, start, end| try { - // Adjusting span endpoints by `BytePos(1)` is normally a bug, - // but in this case we have specifically checked that the character - // we're skipping over is one of two specific ASCII characters, so - // adjusting by exactly 1 byte is correct. - if src.as_bytes().get(end).copied() == Some(b'{') { - Some(span.with_hi(span.hi() + BytePos(1))) - } else if start > 0 && src.as_bytes()[start - 1] == b'}' { - Some(span.with_lo(span.lo() - BytePos(1))) - } else { - None - } - }) - .ok()? -} - /// If `llvm-cov` sees a source region that is improperly ordered (end < start), /// it will immediately exit with a fatal error. To prevent that from happening, /// discard regions that are improperly ordered, or might be interpreted in a diff --git a/compiler/rustc_mir_transform/src/coverage/spans.rs b/compiler/rustc_mir_transform/src/coverage/spans.rs index ec76076020eb7..ddeae093df5b7 100644 --- a/compiler/rustc_mir_transform/src/coverage/spans.rs +++ b/compiler/rustc_mir_transform/src/coverage/spans.rs @@ -1,7 +1,8 @@ use rustc_data_structures::fx::FxHashSet; use rustc_middle::mir; use rustc_middle::ty::TyCtxt; -use rustc_span::{DesugaringKind, ExpnKind, MacroKind, Span}; +use rustc_span::source_map::SourceMap; +use rustc_span::{BytePos, DesugaringKind, ExpnKind, MacroKind, Span}; use tracing::instrument; use crate::coverage::graph::{BasicCoverageBlock, CoverageGraph}; @@ -83,8 +84,18 @@ pub(super) fn extract_refined_covspans<'tcx>( // Discard any span that overlaps with a hole. discard_spans_overlapping_holes(&mut covspans, &holes); - // Perform more refinement steps after holes have been dealt with. + // Discard spans that overlap in unwanted ways. let mut covspans = remove_unwanted_overlapping_spans(covspans); + + // For all empty spans, either enlarge them to be non-empty, or discard them. + let source_map = tcx.sess.source_map(); + covspans.retain_mut(|covspan| { + let Some(span) = ensure_non_empty_span(source_map, covspan.span) else { return false }; + covspan.span = span; + true + }); + + // Merge covspans that can be merged. covspans.dedup_by(|b, a| a.merge_if_eligible(b)); code_mappings.extend(covspans.into_iter().map(|Covspan { span, bcb }| { @@ -230,3 +241,26 @@ fn compare_spans(a: Span, b: Span) -> std::cmp::Ordering { // - Both have the same start and span A extends further right .then_with(|| Ord::cmp(&a.hi(), &b.hi()).reverse()) } + +fn ensure_non_empty_span(source_map: &SourceMap, span: Span) -> Option { + if !span.is_empty() { + return Some(span); + } + + // The span is empty, so try to enlarge it to cover an adjacent '{' or '}'. + source_map + .span_to_source(span, |src, start, end| try { + // Adjusting span endpoints by `BytePos(1)` is normally a bug, + // but in this case we have specifically checked that the character + // we're skipping over is one of two specific ASCII characters, so + // adjusting by exactly 1 byte is correct. + if src.as_bytes().get(end).copied() == Some(b'{') { + Some(span.with_hi(span.hi() + BytePos(1))) + } else if start > 0 && src.as_bytes()[start - 1] == b'}' { + Some(span.with_lo(span.lo() - BytePos(1))) + } else { + None + } + }) + .ok()? +} diff --git a/tests/coverage/async_closure.cov-map b/tests/coverage/async_closure.cov-map index 9f8dc8d6cbbae..53128dd7a48b0 100644 --- a/tests/coverage/async_closure.cov-map +++ b/tests/coverage/async_closure.cov-map @@ -37,32 +37,29 @@ Number of file 0 mappings: 8 Highest counter ID seen: c0 Function name: async_closure::main::{closure#0} -Raw bytes (14): 0x[01, 01, 00, 02, 01, 0b, 22, 00, 23, 01, 00, 23, 00, 24] +Raw bytes (9): 0x[01, 01, 00, 01, 01, 0b, 22, 00, 24] Number of files: 1 - file 0 => $DIR/async_closure.rs Number of expressions: 0 -Number of file 0 mappings: 2 -- Code(Counter(0)) at (prev + 11, 34) to (start + 0, 35) -- Code(Counter(0)) at (prev + 0, 35) to (start + 0, 36) +Number of file 0 mappings: 1 +- Code(Counter(0)) at (prev + 11, 34) to (start + 0, 36) Highest counter ID seen: c0 Function name: async_closure::main::{closure#0} -Raw bytes (14): 0x[01, 01, 00, 02, 01, 0b, 22, 00, 23, 01, 00, 23, 00, 24] +Raw bytes (9): 0x[01, 01, 00, 01, 01, 0b, 22, 00, 24] Number of files: 1 - file 0 => $DIR/async_closure.rs Number of expressions: 0 -Number of file 0 mappings: 2 -- Code(Counter(0)) at (prev + 11, 34) to (start + 0, 35) -- Code(Counter(0)) at (prev + 0, 35) to (start + 0, 36) +Number of file 0 mappings: 1 +- Code(Counter(0)) at (prev + 11, 34) to (start + 0, 36) Highest counter ID seen: c0 Function name: async_closure::main::{closure#0}::{closure#0}:: -Raw bytes (14): 0x[01, 01, 00, 02, 01, 0b, 22, 00, 23, 01, 00, 23, 00, 24] +Raw bytes (9): 0x[01, 01, 00, 01, 01, 0b, 22, 00, 24] Number of files: 1 - file 0 => $DIR/async_closure.rs Number of expressions: 0 -Number of file 0 mappings: 2 -- Code(Counter(0)) at (prev + 11, 34) to (start + 0, 35) -- Code(Counter(0)) at (prev + 0, 35) to (start + 0, 36) +Number of file 0 mappings: 1 +- Code(Counter(0)) at (prev + 11, 34) to (start + 0, 36) Highest counter ID seen: c0 diff --git a/tests/mir-opt/coverage/branch_match_arms.main.InstrumentCoverage.diff b/tests/mir-opt/coverage/branch_match_arms.main.InstrumentCoverage.diff index d465b8bded22f..fa88211383a04 100644 --- a/tests/mir-opt/coverage/branch_match_arms.main.InstrumentCoverage.diff +++ b/tests/mir-opt/coverage/branch_match_arms.main.InstrumentCoverage.diff @@ -40,7 +40,7 @@ + coverage Code { bcb: bcb5 } => $DIR/branch_match_arms.rs:19:17: 19:18 (#0); + coverage Code { bcb: bcb5 } => $DIR/branch_match_arms.rs:19:23: 19:30 (#0); + coverage Code { bcb: bcb5 } => $DIR/branch_match_arms.rs:19:31: 19:32 (#0); -+ coverage Code { bcb: bcb2 } => $DIR/branch_match_arms.rs:21:2: 21:2 (#0); ++ coverage Code { bcb: bcb2 } => $DIR/branch_match_arms.rs:21:1: 21:2 (#0); + bb0: { + Coverage::VirtualCounter(bcb0); diff --git a/tests/mir-opt/coverage/instrument_coverage.bar.InstrumentCoverage.diff b/tests/mir-opt/coverage/instrument_coverage.bar.InstrumentCoverage.diff index cf6d85abd80ef..9b6d2b22087b6 100644 --- a/tests/mir-opt/coverage/instrument_coverage.bar.InstrumentCoverage.diff +++ b/tests/mir-opt/coverage/instrument_coverage.bar.InstrumentCoverage.diff @@ -6,7 +6,7 @@ + coverage Code { bcb: bcb0 } => $DIR/instrument_coverage.rs:27:1: 27:17 (#0); + coverage Code { bcb: bcb0 } => $DIR/instrument_coverage.rs:28:5: 28:9 (#0); -+ coverage Code { bcb: bcb0 } => $DIR/instrument_coverage.rs:29:2: 29:2 (#0); ++ coverage Code { bcb: bcb0 } => $DIR/instrument_coverage.rs:29:1: 29:2 (#0); + bb0: { + Coverage::VirtualCounter(bcb0); diff --git a/tests/mir-opt/coverage/instrument_coverage.main.InstrumentCoverage.diff b/tests/mir-opt/coverage/instrument_coverage.main.InstrumentCoverage.diff index 980c5e202ffd8..b2bb2375aee60 100644 --- a/tests/mir-opt/coverage/instrument_coverage.main.InstrumentCoverage.diff +++ b/tests/mir-opt/coverage/instrument_coverage.main.InstrumentCoverage.diff @@ -10,8 +10,8 @@ + coverage Code { bcb: bcb0 } => $DIR/instrument_coverage.rs:13:1: 13:10 (#0); + coverage Code { bcb: bcb1 } => $DIR/instrument_coverage.rs:15:12: 15:15 (#0); + coverage Code { bcb: bcb2 } => $DIR/instrument_coverage.rs:16:13: 16:18 (#0); -+ coverage Code { bcb: bcb3 } => $DIR/instrument_coverage.rs:17:10: 17:10 (#0); -+ coverage Code { bcb: bcb2 } => $DIR/instrument_coverage.rs:19:2: 19:2 (#0); ++ coverage Code { bcb: bcb3 } => $DIR/instrument_coverage.rs:17:9: 17:10 (#0); ++ coverage Code { bcb: bcb2 } => $DIR/instrument_coverage.rs:19:1: 19:2 (#0); + bb0: { + Coverage::VirtualCounter(bcb0); diff --git a/tests/mir-opt/coverage/instrument_coverage_cleanup.main.CleanupPostBorrowck.diff b/tests/mir-opt/coverage/instrument_coverage_cleanup.main.CleanupPostBorrowck.diff index b707cd41788ac..2eb78c08ee800 100644 --- a/tests/mir-opt/coverage/instrument_coverage_cleanup.main.CleanupPostBorrowck.diff +++ b/tests/mir-opt/coverage/instrument_coverage_cleanup.main.CleanupPostBorrowck.diff @@ -10,8 +10,8 @@ coverage Code { bcb: bcb0 } => $DIR/instrument_coverage_cleanup.rs:13:1: 13:10 (#0); coverage Code { bcb: bcb0 } => $DIR/instrument_coverage_cleanup.rs:14:8: 14:36 (#0); coverage Code { bcb: bcb3 } => $DIR/instrument_coverage_cleanup.rs:14:37: 14:39 (#0); - coverage Code { bcb: bcb1 } => $DIR/instrument_coverage_cleanup.rs:14:39: 14:39 (#0); - coverage Code { bcb: bcb2 } => $DIR/instrument_coverage_cleanup.rs:15:2: 15:2 (#0); + coverage Code { bcb: bcb1 } => $DIR/instrument_coverage_cleanup.rs:14:38: 14:39 (#0); + coverage Code { bcb: bcb2 } => $DIR/instrument_coverage_cleanup.rs:15:1: 15:2 (#0); coverage Branch { true_bcb: bcb3, false_bcb: bcb1 } => $DIR/instrument_coverage_cleanup.rs:14:8: 14:36 (#0); bb0: { diff --git a/tests/mir-opt/coverage/instrument_coverage_cleanup.main.InstrumentCoverage.diff b/tests/mir-opt/coverage/instrument_coverage_cleanup.main.InstrumentCoverage.diff index 239b845c2311e..0c1bc24b6dc19 100644 --- a/tests/mir-opt/coverage/instrument_coverage_cleanup.main.InstrumentCoverage.diff +++ b/tests/mir-opt/coverage/instrument_coverage_cleanup.main.InstrumentCoverage.diff @@ -10,8 +10,8 @@ + coverage Code { bcb: bcb0 } => $DIR/instrument_coverage_cleanup.rs:13:1: 13:10 (#0); + coverage Code { bcb: bcb0 } => $DIR/instrument_coverage_cleanup.rs:14:8: 14:36 (#0); + coverage Code { bcb: bcb3 } => $DIR/instrument_coverage_cleanup.rs:14:37: 14:39 (#0); -+ coverage Code { bcb: bcb1 } => $DIR/instrument_coverage_cleanup.rs:14:39: 14:39 (#0); -+ coverage Code { bcb: bcb2 } => $DIR/instrument_coverage_cleanup.rs:15:2: 15:2 (#0); ++ coverage Code { bcb: bcb1 } => $DIR/instrument_coverage_cleanup.rs:14:38: 14:39 (#0); ++ coverage Code { bcb: bcb2 } => $DIR/instrument_coverage_cleanup.rs:15:1: 15:2 (#0); + coverage Branch { true_bcb: bcb3, false_bcb: bcb1 } => $DIR/instrument_coverage_cleanup.rs:14:8: 14:36 (#0); + bb0: {