coverage. Generate Mappings of decisions and conditions for MC/DC
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zhuyunxing
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68f86381ee
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cf6b6cb2b4
10 changed files with 779 additions and 41 deletions
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@ -1,14 +1,20 @@
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use std::assert_matches::assert_matches;
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use std::collections::hash_map::Entry;
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use std::collections::VecDeque;
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use rustc_data_structures::fx::FxHashMap;
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use rustc_middle::mir::coverage::{BlockMarkerId, BranchSpan, CoverageKind};
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use rustc_middle::mir::coverage::{
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BlockMarkerId, BranchSpan, ConditionId, ConditionInfo, CoverageKind, MCDCBranchSpan,
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MCDCDecisionSpan,
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};
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use rustc_middle::mir::{self, BasicBlock, UnOp};
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use rustc_middle::thir::{ExprId, ExprKind, Thir};
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use rustc_middle::thir::{ExprId, ExprKind, LogicalOp, Thir};
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use rustc_middle::ty::TyCtxt;
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use rustc_span::def_id::LocalDefId;
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use rustc_span::Span;
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use crate::build::Builder;
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use crate::errors::MCDCExceedsConditionNumLimit;
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pub(crate) struct BranchInfoBuilder {
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/// Maps condition expressions to their enclosing `!`, for better instrumentation.
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@ -16,6 +22,9 @@ pub(crate) struct BranchInfoBuilder {
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num_block_markers: usize,
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branch_spans: Vec<BranchSpan>,
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mcdc_branch_spans: Vec<MCDCBranchSpan>,
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mcdc_decision_spans: Vec<MCDCDecisionSpan>,
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mcdc_state: Option<MCDCState>,
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}
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#[derive(Clone, Copy)]
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@ -33,7 +42,14 @@ impl BranchInfoBuilder {
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/// is enabled and `def_id` represents a function that is eligible for coverage.
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pub(crate) fn new_if_enabled(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<Self> {
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if tcx.sess.instrument_coverage_branch() && tcx.is_eligible_for_coverage(def_id) {
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Some(Self { nots: FxHashMap::default(), num_block_markers: 0, branch_spans: vec![] })
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Some(Self {
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nots: FxHashMap::default(),
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num_block_markers: 0,
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branch_spans: vec![],
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mcdc_branch_spans: vec![],
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mcdc_decision_spans: vec![],
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mcdc_state: MCDCState::new_if_enabled(tcx),
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})
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} else {
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None
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}
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@ -79,6 +95,55 @@ impl BranchInfoBuilder {
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}
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}
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fn record_conditions_operation(&mut self, logical_op: LogicalOp, span: Span) {
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if let Some(mcdc_state) = self.mcdc_state.as_mut() {
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mcdc_state.record_conditions(logical_op, span);
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}
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}
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fn fetch_condition_info(
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&mut self,
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tcx: TyCtxt<'_>,
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true_marker: BlockMarkerId,
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false_marker: BlockMarkerId,
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) -> Option<ConditionInfo> {
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let mcdc_state = self.mcdc_state.as_mut()?;
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let (mut condition_info, decision_result) =
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mcdc_state.take_condition(true_marker, false_marker);
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if let Some(decision) = decision_result {
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match decision.conditions_num {
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0 => {
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unreachable!("Decision with no condition is not expected");
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}
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1..=MAX_CONDITIONS_NUM_IN_DECISION => {
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self.mcdc_decision_spans.push(decision);
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}
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_ => {
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// Do not generate mcdc mappings and statements for decisions with too many conditions.
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let rebase_idx = self.mcdc_branch_spans.len() - decision.conditions_num + 1;
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let to_normal_branches = self.mcdc_branch_spans.split_off(rebase_idx);
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self.branch_spans.extend(to_normal_branches.into_iter().map(
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|MCDCBranchSpan { span, true_marker, false_marker, .. }| BranchSpan {
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span,
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true_marker,
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false_marker,
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},
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));
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// ConditionInfo of this branch shall also be reset.
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condition_info = None;
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tcx.dcx().emit_warn(MCDCExceedsConditionNumLimit {
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span: decision.span,
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conditions_num: decision.conditions_num,
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max_conditions_num: MAX_CONDITIONS_NUM_IN_DECISION,
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});
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}
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}
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}
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condition_info
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}
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fn next_block_marker_id(&mut self) -> BlockMarkerId {
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let id = BlockMarkerId::from_usize(self.num_block_markers);
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self.num_block_markers += 1;
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@ -86,14 +151,167 @@ impl BranchInfoBuilder {
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}
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pub(crate) fn into_done(self) -> Option<Box<mir::coverage::BranchInfo>> {
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let Self { nots: _, num_block_markers, branch_spans } = self;
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let Self {
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nots: _,
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num_block_markers,
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branch_spans,
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mcdc_branch_spans,
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mcdc_decision_spans,
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..
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} = self;
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if num_block_markers == 0 {
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assert!(branch_spans.is_empty());
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return None;
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}
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Some(Box::new(mir::coverage::BranchInfo { num_block_markers, branch_spans }))
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Some(Box::new(mir::coverage::BranchInfo {
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num_block_markers,
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branch_spans,
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mcdc_branch_spans,
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mcdc_decision_spans,
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}))
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}
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}
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/// The MCDC bitmap scales exponentially (2^n) based on the number of conditions seen,
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/// So llvm sets a maximum value prevents the bitmap footprint from growing too large without the user's knowledge.
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/// This limit may be relaxed if the [upstream change](https://github.com/llvm/llvm-project/pull/82448) is merged.
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const MAX_CONDITIONS_NUM_IN_DECISION: usize = 6;
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struct MCDCState {
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/// To construct condition evaluation tree.
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decision_stack: VecDeque<ConditionInfo>,
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processing_decision: Option<MCDCDecisionSpan>,
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}
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impl MCDCState {
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fn new_if_enabled(tcx: TyCtxt<'_>) -> Option<Self> {
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tcx.sess
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.instrument_coverage_mcdc()
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.then(|| Self { decision_stack: VecDeque::new(), processing_decision: None })
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}
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// At first we assign ConditionIds for each sub expression.
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// If the sub expression is composite, re-assign its ConditionId to its LHS and generate a new ConditionId for its RHS.
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//
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// Example: "x = (A && B) || (C && D) || (D && F)"
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//
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// Visit Depth1:
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// (A && B) || (C && D) || (D && F)
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// ^-------LHS--------^ ^-RHS--^
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// ID=1 ID=2
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//
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// Visit LHS-Depth2:
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// (A && B) || (C && D)
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// ^-LHS--^ ^-RHS--^
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// ID=1 ID=3
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//
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// Visit LHS-Depth3:
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// (A && B)
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// LHS RHS
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// ID=1 ID=4
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//
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// Visit RHS-Depth3:
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// (C && D)
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// LHS RHS
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// ID=3 ID=5
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//
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// Visit RHS-Depth2: (D && F)
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// LHS RHS
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// ID=2 ID=6
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//
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// Visit Depth1:
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// (A && B) || (C && D) || (D && F)
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// ID=1 ID=4 ID=3 ID=5 ID=2 ID=6
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//
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// A node ID of '0' always means MC/DC isn't being tracked.
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//
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// If a "next" node ID is '0', it means it's the end of the test vector.
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//
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// As the compiler tracks expression in pre-order, we can ensure that condition info of parents are always properly assigned when their children are visited.
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// - If the op is AND, the "false_next" of LHS and RHS should be the parent's "false_next". While "true_next" of the LHS is the RHS, the "true next" of RHS is the parent's "true_next".
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// - If the op is OR, the "true_next" of LHS and RHS should be the parent's "true_next". While "false_next" of the LHS is the RHS, the "false next" of RHS is the parent's "false_next".
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fn record_conditions(&mut self, op: LogicalOp, span: Span) {
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let decision = match self.processing_decision.as_mut() {
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Some(decision) => {
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decision.span = decision.span.to(span);
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decision
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}
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None => self.processing_decision.insert(MCDCDecisionSpan {
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span,
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conditions_num: 0,
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end_markers: vec![],
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}),
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};
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let parent_condition = self.decision_stack.pop_back().unwrap_or_default();
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let lhs_id = if parent_condition.condition_id == ConditionId::NONE {
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decision.conditions_num += 1;
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ConditionId::from(decision.conditions_num)
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} else {
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parent_condition.condition_id
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};
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decision.conditions_num += 1;
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let rhs_condition_id = ConditionId::from(decision.conditions_num);
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let (lhs, rhs) = match op {
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LogicalOp::And => {
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let lhs = ConditionInfo {
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condition_id: lhs_id,
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true_next_id: rhs_condition_id,
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false_next_id: parent_condition.false_next_id,
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};
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let rhs = ConditionInfo {
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condition_id: rhs_condition_id,
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true_next_id: parent_condition.true_next_id,
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false_next_id: parent_condition.false_next_id,
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};
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(lhs, rhs)
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}
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LogicalOp::Or => {
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let lhs = ConditionInfo {
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condition_id: lhs_id,
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true_next_id: parent_condition.true_next_id,
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false_next_id: rhs_condition_id,
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};
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let rhs = ConditionInfo {
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condition_id: rhs_condition_id,
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true_next_id: parent_condition.true_next_id,
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false_next_id: parent_condition.false_next_id,
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};
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(lhs, rhs)
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}
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};
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// We visit expressions tree in pre-order, so place the left-hand side on the top.
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self.decision_stack.push_back(rhs);
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self.decision_stack.push_back(lhs);
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}
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fn take_condition(
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&mut self,
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true_marker: BlockMarkerId,
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false_marker: BlockMarkerId,
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) -> (Option<ConditionInfo>, Option<MCDCDecisionSpan>) {
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let Some(condition_info) = self.decision_stack.pop_back() else {
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return (None, None);
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};
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let Some(decision) = self.processing_decision.as_mut() else {
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bug!("Processing decision should have been created before any conditions are taken");
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};
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if condition_info.true_next_id == ConditionId::NONE {
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decision.end_markers.push(true_marker);
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}
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if condition_info.false_next_id == ConditionId::NONE {
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decision.end_markers.push(false_marker);
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}
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if self.decision_stack.is_empty() {
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(Some(condition_info), self.processing_decision.take())
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} else {
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(Some(condition_info), None)
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}
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}
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}
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@ -137,10 +355,27 @@ impl Builder<'_, '_> {
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let true_marker = inject_branch_marker(then_block);
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let false_marker = inject_branch_marker(else_block);
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branch_info.branch_spans.push(BranchSpan {
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span: source_info.span,
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true_marker,
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false_marker,
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});
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if let Some(condition_info) =
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branch_info.fetch_condition_info(self.tcx, true_marker, false_marker)
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{
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branch_info.mcdc_branch_spans.push(MCDCBranchSpan {
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span: source_info.span,
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condition_info,
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true_marker,
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false_marker,
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});
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} else {
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branch_info.branch_spans.push(BranchSpan {
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span: source_info.span,
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true_marker,
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false_marker,
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});
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}
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}
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pub(crate) fn visit_coverage_branch_operation(&mut self, logical_op: LogicalOp, span: Span) {
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if let Some(branch_info) = self.coverage_branch_info.as_mut() {
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branch_info.record_conditions_operation(logical_op, span);
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}
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}
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}
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@ -77,11 +77,13 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
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match expr.kind {
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ExprKind::LogicalOp { op: LogicalOp::And, lhs, rhs } => {
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this.visit_coverage_branch_operation(LogicalOp::And, expr_span);
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let lhs_then_block = unpack!(this.then_else_break_inner(block, lhs, args));
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let rhs_then_block = unpack!(this.then_else_break_inner(lhs_then_block, rhs, args));
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rhs_then_block.unit()
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}
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ExprKind::LogicalOp { op: LogicalOp::Or, lhs, rhs } => {
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this.visit_coverage_branch_operation(LogicalOp::Or, expr_span);
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let local_scope = this.local_scope();
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let (lhs_success_block, failure_block) =
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this.in_if_then_scope(local_scope, expr_span, |this| {
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