coverage: Split off mappings.rs from spans.rs and from_mir.rs

Author: Zalathar

compiler/rustc_mir_transform/src/coverage/mappings.rs

@@ -0,0 +1,275 @@
+use std::collections::BTreeSet;
+
+use rustc_data_structures::graph::DirectedGraph;
+use rustc_index::bit_set::BitSet;
+use rustc_middle::mir::coverage::{
+    BlockMarkerId, BranchSpan, ConditionInfo, CoverageKind, MCDCBranchSpan, MCDCDecisionSpan,
+};
+use rustc_middle::mir::{self, BasicBlock, StatementKind};
+use rustc_span::Span;
+
+use crate::coverage::graph::{BasicCoverageBlock, CoverageGraph, START_BCB};
+use crate::coverage::spans::{
+    extract_refined_covspans, unexpand_into_body_span_with_visible_macro,
+};
+use crate::coverage::ExtractedHirInfo;
+use rustc_index::IndexVec;
+
+#[derive(Clone, Debug)]
+pub(super) enum BcbMappingKind {
+    /// Associates an ordinary executable code span with its corresponding BCB.
+    Code(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,
+        false_bcb: BasicCoverageBlock,
+        /// If `None`, this actually represents a normal branch mapping inserted
+        /// for code that was too complex for MC/DC.
+        condition_info: Option<ConditionInfo>,
+        decision_depth: u16,
+    },
+    /// Associates a mcdc decision with its join BCB.
+    MCDCDecision {
+        end_bcbs: BTreeSet<BasicCoverageBlock>,
+        bitmap_idx: u32,
+        conditions_num: u16,
+        decision_depth: u16,
+    },
+}
+
+#[derive(Debug)]
+pub(super) struct BcbMapping {
+    pub(super) kind: BcbMappingKind,
+    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>,
+    pub(super) mappings: Vec<BcbMapping>,
+    pub(super) branch_pairs: Vec<BcbBranchPair>,
+    test_vector_bitmap_bytes: u32,
+}
+
+impl CoverageSpans {
+    pub(super) fn bcb_has_coverage_spans(&self, bcb: BasicCoverageBlock) -> bool {
+        self.bcb_has_mappings.contains(bcb)
+    }
+
+    pub(super) fn test_vector_bitmap_bytes(&self) -> u32 {
+        self.test_vector_bitmap_bytes
+    }
+}
+
+/// Extracts coverage-relevant spans from MIR, and associates them with
+/// their corresponding BCBs.
+///
+/// Returns `None` if no coverage-relevant spans could be extracted.
+pub(super) fn generate_coverage_spans(
+    mir_body: &mir::Body<'_>,
+    hir_info: &ExtractedHirInfo,
+    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,
+        // with the user code wrapped in a closure. Any spans in the desugared
+        // outer function will be unhelpful, so just keep the signature span
+        // and ignore all of the spans in the MIR body.
+        if let Some(span) = hir_info.fn_sig_span_extended {
+            mappings.push(BcbMapping { kind: BcbMappingKind::Code(START_BCB), span });
+        }
+    } else {
+        extract_refined_covspans(mir_body, hir_info, basic_coverage_blocks, &mut mappings);
+
+        branch_pairs.extend(extract_branch_pairs(mir_body, hir_info, basic_coverage_blocks));
+
+        mappings.extend(extract_mcdc_mappings(mir_body, hir_info.body_span, basic_coverage_blocks));
+    }
+
+    if mappings.is_empty() && branch_pairs.is_empty() {
+        return None;
+    }
+
+    // Identify which BCBs have one or more mappings.
+    let mut bcb_has_mappings = BitSet::new_empty(basic_coverage_blocks.num_nodes());
+    let mut insert = |bcb| {
+        bcb_has_mappings.insert(bcb);
+    };
+    let mut test_vector_bitmap_bytes = 0;
+    for BcbMapping { kind, span: _ } in &mappings {
+        match *kind {
+            BcbMappingKind::Code(bcb) => insert(bcb),
+            BcbMappingKind::MCDCBranch { true_bcb, false_bcb, .. } => {
+                insert(true_bcb);
+                insert(false_bcb);
+            }
+            BcbMappingKind::MCDCDecision { bitmap_idx, conditions_num, .. } => {
+                // `bcb_has_mappings` is used for inject coverage counters
+                // but they are not needed for decision BCBs.
+                // While the length of test vector bitmap should be calculated here.
+                test_vector_bitmap_bytes = test_vector_bitmap_bytes
+                    .max(bitmap_idx + (1_u32 << conditions_num as u32).div_ceil(8));
+            }
+        }
+    }
+    for &BcbBranchPair { true_bcb, false_bcb, .. } in &branch_pairs {
+        insert(true_bcb);
+        insert(false_bcb);
+    }
+
+    Some(CoverageSpans { bcb_has_mappings, mappings, branch_pairs, test_vector_bitmap_bytes })
+}
+
+fn resolve_block_markers(
+    branch_info: &mir::coverage::BranchInfo,
+    mir_body: &mir::Body<'_>,
+) -> IndexVec<BlockMarkerId, Option<BasicBlock>> {
+    let mut block_markers = IndexVec::<BlockMarkerId, Option<BasicBlock>>::from_elem_n(
+        None,
+        branch_info.num_block_markers,
+    );
+
+    // Fill out the mapping from block marker IDs to their enclosing blocks.
+    for (bb, data) in mir_body.basic_blocks.iter_enumerated() {
+        for statement in &data.statements {
+            if let StatementKind::Coverage(CoverageKind::BlockMarker { id }) = statement.kind {
+                block_markers[id] = Some(bb);
+            }
+        }
+    }
+
+    block_markers
+}
+
+// FIXME: There is currently a lot of redundancy between
+// `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_pairs(
+    mir_body: &mir::Body<'_>,
+    hir_info: &ExtractedHirInfo,
+    basic_coverage_blocks: &CoverageGraph,
+) -> 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);
+
+    branch_info
+        .branch_spans
+        .iter()
+        .filter_map(|&BranchSpan { span: raw_span, true_marker, false_marker }| {
+            // For now, ignore any branch span that was introduced by
+            // expansion. This makes things like assert macros less noisy.
+            if !raw_span.ctxt().outer_expn_data().is_root() {
+                return None;
+            }
+            let (span, _) =
+                unexpand_into_body_span_with_visible_macro(raw_span, hir_info.body_span)?;
+
+            let bcb_from_marker =
+                |marker: BlockMarkerId| basic_coverage_blocks.bcb_from_bb(block_markers[marker]?);
+
+            let true_bcb = bcb_from_marker(true_marker)?;
+            let false_bcb = bcb_from_marker(false_marker)?;
+
+            Some(BcbBranchPair { span, true_bcb, false_bcb })
+        })
+        .collect::<Vec<_>>()
+}
+
+pub(super) fn extract_mcdc_mappings(
+    mir_body: &mir::Body<'_>,
+    body_span: Span,
+    basic_coverage_blocks: &CoverageGraph,
+) -> Vec<BcbMapping> {
+    let Some(branch_info) = mir_body.coverage_branch_info.as_deref() else {
+        return vec![];
+    };
+
+    let block_markers = resolve_block_markers(branch_info, mir_body);
+
+    let bcb_from_marker =
+        |marker: BlockMarkerId| basic_coverage_blocks.bcb_from_bb(block_markers[marker]?);
+
+    let check_branch_bcb =
+        |raw_span: Span, true_marker: BlockMarkerId, false_marker: BlockMarkerId| {
+            // For now, ignore any branch span that was introduced by
+            // expansion. This makes things like assert macros less noisy.
+            if !raw_span.ctxt().outer_expn_data().is_root() {
+                return None;
+            }
+            let (span, _) = unexpand_into_body_span_with_visible_macro(raw_span, body_span)?;
+
+            let true_bcb = bcb_from_marker(true_marker)?;
+            let false_bcb = bcb_from_marker(false_marker)?;
+            Some((span, true_bcb, false_bcb))
+        };
+
+    let mcdc_branch_filter_map = |&MCDCBranchSpan {
+                                      span: raw_span,
+                                      true_marker,
+                                      false_marker,
+                                      condition_info,
+                                      decision_depth,
+                                  }| {
+        check_branch_bcb(raw_span, true_marker, false_marker).map(|(span, true_bcb, false_bcb)| {
+            BcbMapping {
+                kind: BcbMappingKind::MCDCBranch {
+                    true_bcb,
+                    false_bcb,
+                    condition_info,
+                    decision_depth,
+                },
+                span,
+            }
+        })
+    };
+
+    let mut next_bitmap_idx = 0;
+
+    let decision_filter_map = |decision: &MCDCDecisionSpan| {
+        let (span, _) = unexpand_into_body_span_with_visible_macro(decision.span, body_span)?;
+
+        let end_bcbs = decision
+            .end_markers
+            .iter()
+            .map(|&marker| bcb_from_marker(marker))
+            .collect::<Option<_>>()?;
+
+        let bitmap_idx = next_bitmap_idx;
+        next_bitmap_idx += (1_u32 << decision.conditions_num).div_ceil(8);
+
+        Some(BcbMapping {
+            kind: BcbMappingKind::MCDCDecision {
+                end_bcbs,
+                bitmap_idx,
+                conditions_num: decision.conditions_num as u16,
+                decision_depth: decision.decision_depth,
+            },
+            span,
+        })
+    };
+
+    std::iter::empty()
+        .chain(branch_info.mcdc_branch_spans.iter().filter_map(mcdc_branch_filter_map))
+        .chain(branch_info.mcdc_decision_spans.iter().filter_map(decision_filter_map))
+        .collect::<Vec<_>>()
+}

compiler/rustc_mir_transform/src/coverage/mod.rs

@@ -2,13 +2,14 @@ pub mod query;
 
 mod counters;
 mod graph;
+mod mappings;
 mod spans;
 #[cfg(test)]
 mod tests;
 
 use self::counters::{CounterIncrementSite, CoverageCounters};
 use self::graph::{BasicCoverageBlock, CoverageGraph};
-use self::spans::{BcbBranchPair, BcbMapping, BcbMappingKind, CoverageSpans};
+use self::mappings::{BcbBranchPair, BcbMapping, BcbMappingKind, CoverageSpans};
 
 use crate::MirPass;
 
@@ -70,7 +71,7 @@ fn instrument_function_for_coverage<'tcx>(tcx: TyCtxt<'tcx>, mir_body: &mut mir:
     ////////////////////////////////////////////////////
     // Compute coverage spans from the `CoverageGraph`.
     let Some(coverage_spans) =
-        spans::generate_coverage_spans(mir_body, &hir_info, &basic_coverage_blocks)
+        mappings::generate_coverage_spans(mir_body, &hir_info, &basic_coverage_blocks)
     else {
         // No relevant spans were found in MIR, so skip instrumenting this function.
         return;