rustc_mir_transform/coverage/
mappings.rs

1use rustc_index::IndexVec;
2use rustc_middle::mir::coverage::{
3    BlockMarkerId, BranchSpan, CoverageInfoHi, CoverageKind, Mapping, MappingKind,
4};
5use rustc_middle::mir::{self, BasicBlock, StatementKind};
6use rustc_middle::ty::TyCtxt;
7use rustc_span::ExpnKind;
8
9use crate::coverage::expansion::{self, ExpnTree};
10use crate::coverage::graph::CoverageGraph;
11use crate::coverage::hir_info::ExtractedHirInfo;
12use crate::coverage::spans::extract_refined_covspans;
13
14#[derive(Default)]
15pub(crate) struct ExtractedMappings {
16    pub(crate) mappings: Vec<Mapping>,
17}
18
19/// Extracts coverage-relevant spans from MIR, and uses them to create
20/// coverage mapping data for inclusion in MIR.
21pub(crate) fn extract_mappings_from_mir<'tcx>(
22    tcx: TyCtxt<'tcx>,
23    mir_body: &mir::Body<'tcx>,
24    hir_info: &ExtractedHirInfo,
25    graph: &CoverageGraph,
26) -> ExtractedMappings {
27    let expn_tree = expansion::build_expn_tree(mir_body, hir_info, graph);
28
29    let mut mappings = vec![];
30
31    // Extract ordinary code mappings from MIR statement/terminator spans.
32    extract_refined_covspans(tcx, hir_info, graph, &expn_tree, &mut mappings);
33
34    extract_branch_mappings(mir_body, hir_info, graph, &expn_tree, &mut mappings);
35
36    ExtractedMappings { mappings }
37}
38
39fn resolve_block_markers(
40    coverage_info_hi: &CoverageInfoHi,
41    mir_body: &mir::Body<'_>,
42) -> IndexVec<BlockMarkerId, Option<BasicBlock>> {
43    let mut block_markers = IndexVec::<BlockMarkerId, Option<BasicBlock>>::from_elem_n(
44        None,
45        coverage_info_hi.num_block_markers,
46    );
47
48    // Fill out the mapping from block marker IDs to their enclosing blocks.
49    for (bb, data) in mir_body.basic_blocks.iter_enumerated() {
50        for statement in &data.statements {
51            if let StatementKind::Coverage(CoverageKind::BlockMarker { id }) = statement.kind {
52                block_markers[id] = Some(bb);
53            }
54        }
55    }
56
57    block_markers
58}
59
60fn extract_branch_mappings(
61    mir_body: &mir::Body<'_>,
62    hir_info: &ExtractedHirInfo,
63    graph: &CoverageGraph,
64    expn_tree: &ExpnTree,
65    mappings: &mut Vec<Mapping>,
66) {
67    let Some(coverage_info_hi) = mir_body.coverage_info_hi.as_deref() else { return };
68    let block_markers = resolve_block_markers(coverage_info_hi, mir_body);
69
70    // For now, ignore any branch span that was introduced by
71    // expansion. This makes things like assert macros less noisy.
72    let Some(node) = expn_tree.get(hir_info.body_span.ctxt().outer_expn()) else { return };
73    if node.expn_kind != ExpnKind::Root {
74        return;
75    }
76
77    mappings.extend(node.branch_spans.iter().filter_map(
78        |&BranchSpan { span, true_marker, false_marker }| try {
79            let bcb_from_marker = |marker: BlockMarkerId| graph.bcb_from_bb(block_markers[marker]?);
80
81            let true_bcb = bcb_from_marker(true_marker)?;
82            let false_bcb = bcb_from_marker(false_marker)?;
83
84            Mapping { span, kind: MappingKind::Branch { true_bcb, false_bcb } }
85        },
86    ));
87}
rustc_mir_transform/coverage/mappings.rs

rustc_mir_transform/coverage/
mappings.rs
