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coverage: Separate branch pairs from other mapping kinds
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This clears the way for larger changes to how branches are handled by the
coverage instrumentor, in order to support branch coverage for more language
constructs.
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Zalathar committed Apr 21, 2024
1 parent 999e192 commit 3a6c74b
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Showing 3 changed files with 44 additions and 25 deletions.
22 changes: 14 additions & 8 deletions compiler/rustc_mir_transform/src/coverage/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,7 @@ mod tests;

use self::counters::{CounterIncrementSite, CoverageCounters};
use self::graph::{BasicCoverageBlock, CoverageGraph};
use self::spans::{BcbMapping, BcbMappingKind, CoverageSpans};
use self::spans::{BcbBranchPair, BcbMapping, BcbMappingKind, CoverageSpans};

use crate::MirPass;

Expand Down Expand Up @@ -141,14 +141,10 @@ fn create_mappings<'tcx>(

let mut mappings = Vec::new();

mappings.extend(coverage_spans.all_bcb_mappings().filter_map(
mappings.extend(coverage_spans.mappings.iter().filter_map(
|BcbMapping { kind: bcb_mapping_kind, span }| {
let kind = match *bcb_mapping_kind {
BcbMappingKind::Code(bcb) => MappingKind::Code(term_for_bcb(bcb)),
BcbMappingKind::Branch { true_bcb, false_bcb } => MappingKind::Branch {
true_term: term_for_bcb(true_bcb),
false_term: term_for_bcb(false_bcb),
},
BcbMappingKind::MCDCBranch { true_bcb, false_bcb, condition_info: None } => {
MappingKind::Branch {
true_term: term_for_bcb(true_bcb),
Expand All @@ -173,6 +169,16 @@ fn create_mappings<'tcx>(
},
));

mappings.extend(coverage_spans.branch_pairs.iter().filter_map(
|&BcbBranchPair { span, true_bcb, false_bcb }| {
let true_term = term_for_bcb(true_bcb);
let false_term = term_for_bcb(false_bcb);
let kind = MappingKind::Branch { true_term, false_term };
let code_region = make_code_region(source_map, file_name, span, body_span)?;
Some(Mapping { kind, code_region })
},
));

mappings
}

Expand Down Expand Up @@ -241,7 +247,7 @@ fn inject_mcdc_statements<'tcx>(

// Inject test vector update first because `inject_statement` always insert new statement at head.
for (end_bcbs, bitmap_idx) in
coverage_spans.all_bcb_mappings().filter_map(|mapping| match &mapping.kind {
coverage_spans.mappings.iter().filter_map(|mapping| match &mapping.kind {
BcbMappingKind::MCDCDecision { end_bcbs, bitmap_idx, .. } => {
Some((end_bcbs, *bitmap_idx))
}
Expand All @@ -255,7 +261,7 @@ fn inject_mcdc_statements<'tcx>(
}

for (true_bcb, false_bcb, condition_id) in
coverage_spans.all_bcb_mappings().filter_map(|mapping| match mapping.kind {
coverage_spans.mappings.iter().filter_map(|mapping| match mapping.kind {
BcbMappingKind::MCDCBranch { true_bcb, false_bcb, condition_info } => {
Some((true_bcb, false_bcb, condition_info?.condition_id))
}
Expand Down
37 changes: 25 additions & 12 deletions compiler/rustc_mir_transform/src/coverage/spans.rs
Original file line number Diff line number Diff line change
Expand Up @@ -15,8 +15,10 @@ mod from_mir;
pub(super) enum BcbMappingKind {
/// Associates an ordinary executable code span with its corresponding BCB.
Code(BasicCoverageBlock),
/// Associates a branch span with BCBs for its true and false arms.
Branch { true_bcb: BasicCoverageBlock, false_bcb: BasicCoverageBlock },

// Ordinary branch mappings are stored separately, so they don't have a
// variant in this enum.
//
/// Associates a mcdc branch span with condition info besides fields for normal branch.
MCDCBranch {
true_bcb: BasicCoverageBlock,
Expand All @@ -35,9 +37,20 @@ pub(super) struct BcbMapping {
pub(super) span: Span,
}

/// This is separate from [`BcbMappingKind`] to help prepare for larger changes
/// that will be needed for improved branch coverage in the future.
/// (See <https://github.com/rust-lang/rust/pull/124217>.)
#[derive(Debug)]
pub(super) struct BcbBranchPair {
pub(super) span: Span,
pub(super) true_bcb: BasicCoverageBlock,
pub(super) false_bcb: BasicCoverageBlock,
}

pub(super) struct CoverageSpans {
bcb_has_mappings: BitSet<BasicCoverageBlock>,
mappings: Vec<BcbMapping>,
pub(super) mappings: Vec<BcbMapping>,
pub(super) branch_pairs: Vec<BcbBranchPair>,
test_vector_bitmap_bytes: u32,
}

Expand All @@ -46,10 +59,6 @@ impl CoverageSpans {
self.bcb_has_mappings.contains(bcb)
}

pub(super) fn all_bcb_mappings(&self) -> impl Iterator<Item = &BcbMapping> {
self.mappings.iter()
}

pub(super) fn test_vector_bitmap_bytes(&self) -> u32 {
self.test_vector_bitmap_bytes
}
Expand All @@ -65,6 +74,7 @@ pub(super) fn generate_coverage_spans(
basic_coverage_blocks: &CoverageGraph,
) -> Option<CoverageSpans> {
let mut mappings = vec![];
let mut branch_pairs = vec![];

if hir_info.is_async_fn {
// An async function desugars into a function that returns a future,
Expand All @@ -86,7 +96,7 @@ pub(super) fn generate_coverage_spans(
BcbMapping { kind: BcbMappingKind::Code(bcb), span }
}));

mappings.extend(from_mir::extract_branch_mappings(
branch_pairs.extend(from_mir::extract_branch_pairs(
mir_body,
hir_info.body_span,
basic_coverage_blocks,
Expand All @@ -99,7 +109,7 @@ pub(super) fn generate_coverage_spans(
));
}

if mappings.is_empty() {
if mappings.is_empty() && branch_pairs.is_empty() {
return None;
}

Expand All @@ -112,8 +122,7 @@ pub(super) fn generate_coverage_spans(
for BcbMapping { kind, span: _ } in &mappings {
match *kind {
BcbMappingKind::Code(bcb) => insert(bcb),
BcbMappingKind::Branch { true_bcb, false_bcb }
| BcbMappingKind::MCDCBranch { true_bcb, false_bcb, .. } => {
BcbMappingKind::MCDCBranch { true_bcb, false_bcb, .. } => {
insert(true_bcb);
insert(false_bcb);
}
Expand All @@ -126,8 +135,12 @@ pub(super) fn generate_coverage_spans(
}
}
}
for &BcbBranchPair { true_bcb, false_bcb, .. } in &branch_pairs {
insert(true_bcb);
insert(false_bcb);
}

Some(CoverageSpans { bcb_has_mappings, mappings, test_vector_bitmap_bytes })
Some(CoverageSpans { bcb_has_mappings, mappings, branch_pairs, test_vector_bitmap_bytes })
}

#[derive(Debug)]
Expand Down
10 changes: 5 additions & 5 deletions compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs
Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,7 @@ use rustc_span::{ExpnKind, MacroKind, Span, Symbol};
use crate::coverage::graph::{
BasicCoverageBlock, BasicCoverageBlockData, CoverageGraph, START_BCB,
};
use crate::coverage::spans::{BcbMapping, BcbMappingKind};
use crate::coverage::spans::{BcbBranchPair, BcbMapping, BcbMappingKind};
use crate::coverage::ExtractedHirInfo;

/// Traverses the MIR body to produce an initial collection of coverage-relevant
Expand Down Expand Up @@ -388,16 +388,16 @@ fn resolve_block_markers(
}

// FIXME: There is currently a lot of redundancy between
// `extract_branch_mappings` and `extract_mcdc_mappings`. This is needed so
// `extract_branch_pairs` and `extract_mcdc_mappings`. This is needed so
// that they can each be modified without interfering with the other, but in
// the long term we should try to bring them together again when branch coverage
// and MC/DC coverage support are more mature.

pub(super) fn extract_branch_mappings(
pub(super) fn extract_branch_pairs(
mir_body: &mir::Body<'_>,
body_span: Span,
basic_coverage_blocks: &CoverageGraph,
) -> Vec<BcbMapping> {
) -> Vec<BcbBranchPair> {
let Some(branch_info) = mir_body.coverage_branch_info.as_deref() else { return vec![] };

let block_markers = resolve_block_markers(branch_info, mir_body);
Expand All @@ -419,7 +419,7 @@ pub(super) fn extract_branch_mappings(
let true_bcb = bcb_from_marker(true_marker)?;
let false_bcb = bcb_from_marker(false_marker)?;

Some(BcbMapping { kind: BcbMappingKind::Branch { true_bcb, false_bcb }, span })
Some(BcbBranchPair { span, true_bcb, false_bcb })
})
.collect::<Vec<_>>()
}
Expand Down

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