1a014d42f4
Because the three kinds of operand are now distinguished explicitly, we no longer need fiddly code to disambiguate counter IDs and expression IDs based on the total number of counters/expressions in a function. This does increase the size of operands from 4 bytes to 8 bytes, but that shouldn't be a big deal since they are mostly stored inside boxed structures, and the current coverage code is not particularly size-optimized anyway.
731 lines
29 KiB
Rust
731 lines
29 KiB
Rust
use super::Error;
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use itertools::Itertools;
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use rustc_data_structures::fx::FxHashMap;
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use rustc_data_structures::graph::dominators::{self, Dominators};
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use rustc_data_structures::graph::{self, GraphSuccessors, WithNumNodes, WithStartNode};
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use rustc_index::bit_set::BitSet;
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use rustc_index::{IndexSlice, IndexVec};
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use rustc_middle::mir::coverage::*;
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use rustc_middle::mir::{self, BasicBlock, BasicBlockData, Terminator, TerminatorKind};
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use std::cmp::Ordering;
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use std::ops::{Index, IndexMut};
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const ID_SEPARATOR: &str = ",";
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/// A coverage-specific simplification of the MIR control flow graph (CFG). The `CoverageGraph`s
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/// nodes are `BasicCoverageBlock`s, which encompass one or more MIR `BasicBlock`s, plus a
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/// `CoverageKind` counter (to be added by `CoverageCounters::make_bcb_counters`), and an optional
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/// set of additional counters--if needed--to count incoming edges, if there are more than one.
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/// (These "edge counters" are eventually converted into new MIR `BasicBlock`s.)
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#[derive(Debug)]
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pub(super) struct CoverageGraph {
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bcbs: IndexVec<BasicCoverageBlock, BasicCoverageBlockData>,
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bb_to_bcb: IndexVec<BasicBlock, Option<BasicCoverageBlock>>,
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pub successors: IndexVec<BasicCoverageBlock, Vec<BasicCoverageBlock>>,
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pub predecessors: IndexVec<BasicCoverageBlock, Vec<BasicCoverageBlock>>,
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dominators: Option<Dominators<BasicCoverageBlock>>,
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}
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impl CoverageGraph {
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pub fn from_mir(mir_body: &mir::Body<'_>) -> Self {
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let (bcbs, bb_to_bcb) = Self::compute_basic_coverage_blocks(mir_body);
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// Pre-transform MIR `BasicBlock` successors and predecessors into the BasicCoverageBlock
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// equivalents. Note that since the BasicCoverageBlock graph has been fully simplified, the
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// each predecessor of a BCB leader_bb should be in a unique BCB. It is possible for a
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// `SwitchInt` to have multiple targets to the same destination `BasicBlock`, so
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// de-duplication is required. This is done without reordering the successors.
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let mut seen = IndexVec::from_elem(false, &bcbs);
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let successors = IndexVec::from_fn_n(
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|bcb| {
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for b in seen.iter_mut() {
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*b = false;
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}
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let bcb_data = &bcbs[bcb];
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let mut bcb_successors = Vec::new();
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for successor in
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bcb_filtered_successors(&mir_body, &bcb_data.terminator(mir_body).kind)
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.filter_map(|successor_bb| bb_to_bcb[successor_bb])
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{
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if !seen[successor] {
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seen[successor] = true;
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bcb_successors.push(successor);
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}
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}
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bcb_successors
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},
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bcbs.len(),
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);
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let mut predecessors = IndexVec::from_elem(Vec::new(), &bcbs);
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for (bcb, bcb_successors) in successors.iter_enumerated() {
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for &successor in bcb_successors {
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predecessors[successor].push(bcb);
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}
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}
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let mut basic_coverage_blocks =
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Self { bcbs, bb_to_bcb, successors, predecessors, dominators: None };
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let dominators = dominators::dominators(&basic_coverage_blocks);
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basic_coverage_blocks.dominators = Some(dominators);
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basic_coverage_blocks
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}
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fn compute_basic_coverage_blocks(
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mir_body: &mir::Body<'_>,
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) -> (
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IndexVec<BasicCoverageBlock, BasicCoverageBlockData>,
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IndexVec<BasicBlock, Option<BasicCoverageBlock>>,
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) {
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let num_basic_blocks = mir_body.basic_blocks.len();
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let mut bcbs = IndexVec::with_capacity(num_basic_blocks);
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let mut bb_to_bcb = IndexVec::from_elem_n(None, num_basic_blocks);
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// Walk the MIR CFG using a Preorder traversal, which starts from `START_BLOCK` and follows
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// each block terminator's `successors()`. Coverage spans must map to actual source code,
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// so compiler generated blocks and paths can be ignored. To that end, the CFG traversal
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// intentionally omits unwind paths.
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// FIXME(#78544): MIR InstrumentCoverage: Improve coverage of `#[should_panic]` tests and
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// `catch_unwind()` handlers.
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let mir_cfg_without_unwind = ShortCircuitPreorder::new(&mir_body, bcb_filtered_successors);
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let mut basic_blocks = Vec::new();
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for (bb, data) in mir_cfg_without_unwind {
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if let Some(last) = basic_blocks.last() {
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let predecessors = &mir_body.basic_blocks.predecessors()[bb];
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if predecessors.len() > 1 || !predecessors.contains(last) {
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// The `bb` has more than one _incoming_ edge, and should start its own
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// `BasicCoverageBlockData`. (Note, the `basic_blocks` vector does not yet
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// include `bb`; it contains a sequence of one or more sequential basic_blocks
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// with no intermediate branches in or out. Save these as a new
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// `BasicCoverageBlockData` before starting the new one.)
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Self::add_basic_coverage_block(
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&mut bcbs,
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&mut bb_to_bcb,
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basic_blocks.split_off(0),
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);
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debug!(
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" because {}",
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if predecessors.len() > 1 {
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"predecessors.len() > 1".to_owned()
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} else {
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format!("bb {} is not in predecessors: {:?}", bb.index(), predecessors)
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}
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);
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}
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}
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basic_blocks.push(bb);
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let term = data.terminator();
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match term.kind {
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TerminatorKind::Return { .. }
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| TerminatorKind::Terminate
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| TerminatorKind::Yield { .. }
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| TerminatorKind::SwitchInt { .. } => {
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// The `bb` has more than one _outgoing_ edge, or exits the function. Save the
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// current sequence of `basic_blocks` gathered to this point, as a new
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// `BasicCoverageBlockData`.
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Self::add_basic_coverage_block(
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&mut bcbs,
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&mut bb_to_bcb,
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basic_blocks.split_off(0),
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);
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debug!(" because term.kind = {:?}", term.kind);
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// Note that this condition is based on `TerminatorKind`, even though it
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// theoretically boils down to `successors().len() != 1`; that is, either zero
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// (e.g., `Return`, `Terminate`) or multiple successors (e.g., `SwitchInt`), but
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// since the BCB CFG ignores things like unwind branches (which exist in the
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// `Terminator`s `successors()` list) checking the number of successors won't
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// work.
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}
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// The following `TerminatorKind`s are either not expected outside an unwind branch,
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// or they should not (under normal circumstances) branch. Coverage graphs are
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// simplified by assuring coverage results are accurate for program executions that
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// don't panic.
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//
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// Programs that panic and unwind may record slightly inaccurate coverage results
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// for a coverage region containing the `Terminator` that began the panic. This
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// is as intended. (See Issue #78544 for a possible future option to support
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// coverage in test programs that panic.)
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TerminatorKind::Goto { .. }
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| TerminatorKind::Resume
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| TerminatorKind::Unreachable
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| TerminatorKind::Drop { .. }
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| TerminatorKind::Call { .. }
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| TerminatorKind::GeneratorDrop
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| TerminatorKind::Assert { .. }
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| TerminatorKind::FalseEdge { .. }
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| TerminatorKind::FalseUnwind { .. }
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| TerminatorKind::InlineAsm { .. } => {}
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}
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}
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if !basic_blocks.is_empty() {
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// process any remaining basic_blocks into a final `BasicCoverageBlockData`
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Self::add_basic_coverage_block(&mut bcbs, &mut bb_to_bcb, basic_blocks.split_off(0));
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debug!(" because the end of the MIR CFG was reached while traversing");
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}
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(bcbs, bb_to_bcb)
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}
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fn add_basic_coverage_block(
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bcbs: &mut IndexVec<BasicCoverageBlock, BasicCoverageBlockData>,
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bb_to_bcb: &mut IndexSlice<BasicBlock, Option<BasicCoverageBlock>>,
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basic_blocks: Vec<BasicBlock>,
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) {
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let bcb = bcbs.next_index();
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for &bb in basic_blocks.iter() {
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bb_to_bcb[bb] = Some(bcb);
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}
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let bcb_data = BasicCoverageBlockData::from(basic_blocks);
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debug!("adding bcb{}: {:?}", bcb.index(), bcb_data);
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bcbs.push(bcb_data);
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}
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#[inline(always)]
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pub fn iter_enumerated(
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&self,
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) -> impl Iterator<Item = (BasicCoverageBlock, &BasicCoverageBlockData)> {
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self.bcbs.iter_enumerated()
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}
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#[inline(always)]
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pub fn iter_enumerated_mut(
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&mut self,
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) -> impl Iterator<Item = (BasicCoverageBlock, &mut BasicCoverageBlockData)> {
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self.bcbs.iter_enumerated_mut()
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}
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#[inline(always)]
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pub fn bcb_from_bb(&self, bb: BasicBlock) -> Option<BasicCoverageBlock> {
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if bb.index() < self.bb_to_bcb.len() { self.bb_to_bcb[bb] } else { None }
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}
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#[inline(always)]
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pub fn dominates(&self, dom: BasicCoverageBlock, node: BasicCoverageBlock) -> bool {
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self.dominators.as_ref().unwrap().dominates(dom, node)
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}
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#[inline(always)]
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pub fn rank_partial_cmp(
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&self,
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a: BasicCoverageBlock,
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b: BasicCoverageBlock,
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) -> Option<Ordering> {
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self.dominators.as_ref().unwrap().rank_partial_cmp(a, b)
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}
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}
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impl Index<BasicCoverageBlock> for CoverageGraph {
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type Output = BasicCoverageBlockData;
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#[inline]
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fn index(&self, index: BasicCoverageBlock) -> &BasicCoverageBlockData {
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&self.bcbs[index]
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}
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}
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impl IndexMut<BasicCoverageBlock> for CoverageGraph {
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#[inline]
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fn index_mut(&mut self, index: BasicCoverageBlock) -> &mut BasicCoverageBlockData {
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&mut self.bcbs[index]
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}
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}
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impl graph::DirectedGraph for CoverageGraph {
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type Node = BasicCoverageBlock;
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}
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impl graph::WithNumNodes for CoverageGraph {
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#[inline]
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fn num_nodes(&self) -> usize {
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self.bcbs.len()
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}
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}
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impl graph::WithStartNode for CoverageGraph {
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#[inline]
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fn start_node(&self) -> Self::Node {
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self.bcb_from_bb(mir::START_BLOCK)
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.expect("mir::START_BLOCK should be in a BasicCoverageBlock")
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}
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}
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type BcbSuccessors<'graph> = std::slice::Iter<'graph, BasicCoverageBlock>;
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impl<'graph> graph::GraphSuccessors<'graph> for CoverageGraph {
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type Item = BasicCoverageBlock;
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type Iter = std::iter::Cloned<BcbSuccessors<'graph>>;
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}
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impl graph::WithSuccessors for CoverageGraph {
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#[inline]
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fn successors(&self, node: Self::Node) -> <Self as GraphSuccessors<'_>>::Iter {
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self.successors[node].iter().cloned()
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}
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}
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impl<'graph> graph::GraphPredecessors<'graph> for CoverageGraph {
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type Item = BasicCoverageBlock;
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type Iter = std::iter::Copied<std::slice::Iter<'graph, BasicCoverageBlock>>;
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}
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impl graph::WithPredecessors for CoverageGraph {
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#[inline]
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fn predecessors(&self, node: Self::Node) -> <Self as graph::GraphPredecessors<'_>>::Iter {
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self.predecessors[node].iter().copied()
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}
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}
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rustc_index::newtype_index! {
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/// A node in the control-flow graph of CoverageGraph.
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#[debug_format = "bcb{}"]
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pub(super) struct BasicCoverageBlock {
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const START_BCB = 0;
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}
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}
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/// `BasicCoverageBlockData` holds the data indexed by a `BasicCoverageBlock`.
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///
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/// A `BasicCoverageBlock` (BCB) represents the maximal-length sequence of MIR `BasicBlock`s without
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/// conditional branches, and form a new, simplified, coverage-specific Control Flow Graph, without
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/// altering the original MIR CFG.
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///
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/// Note that running the MIR `SimplifyCfg` transform is not sufficient (and therefore not
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/// necessary). The BCB-based CFG is a more aggressive simplification. For example:
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///
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/// * The BCB CFG ignores (trims) branches not relevant to coverage, such as unwind-related code,
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/// that is injected by the Rust compiler but has no physical source code to count. This also
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/// means a BasicBlock with a `Call` terminator can be merged into its primary successor target
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/// block, in the same BCB. (But, note: Issue #78544: "MIR InstrumentCoverage: Improve coverage
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/// of `#[should_panic]` tests and `catch_unwind()` handlers")
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/// * Some BasicBlock terminators support Rust-specific concerns--like borrow-checking--that are
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/// not relevant to coverage analysis. `FalseUnwind`, for example, can be treated the same as
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/// a `Goto`, and merged with its successor into the same BCB.
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///
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/// Each BCB with at least one computed `CoverageSpan` will have no more than one `Counter`.
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/// In some cases, a BCB's execution count can be computed by `Expression`. Additional
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/// disjoint `CoverageSpan`s in a BCB can also be counted by `Expression` (by adding `ZERO`
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/// to the BCB's primary counter or expression).
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///
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/// The BCB CFG is critical to simplifying the coverage analysis by ensuring graph path-based
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/// queries (`dominates()`, `predecessors`, `successors`, etc.) have branch (control flow)
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/// significance.
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#[derive(Debug, Clone)]
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pub(super) struct BasicCoverageBlockData {
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pub basic_blocks: Vec<BasicBlock>,
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pub counter_kind: Option<CoverageKind>,
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edge_from_bcbs: Option<FxHashMap<BasicCoverageBlock, CoverageKind>>,
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}
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impl BasicCoverageBlockData {
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pub fn from(basic_blocks: Vec<BasicBlock>) -> Self {
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assert!(basic_blocks.len() > 0);
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Self { basic_blocks, counter_kind: None, edge_from_bcbs: None }
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}
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#[inline(always)]
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pub fn leader_bb(&self) -> BasicBlock {
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self.basic_blocks[0]
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}
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#[inline(always)]
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pub fn last_bb(&self) -> BasicBlock {
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*self.basic_blocks.last().unwrap()
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}
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#[inline(always)]
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pub fn terminator<'a, 'tcx>(&self, mir_body: &'a mir::Body<'tcx>) -> &'a Terminator<'tcx> {
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&mir_body[self.last_bb()].terminator()
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}
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pub fn set_counter(&mut self, counter_kind: CoverageKind) -> Result<Operand, Error> {
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debug_assert!(
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// If the BCB has an edge counter (to be injected into a new `BasicBlock`), it can also
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// have an expression (to be injected into an existing `BasicBlock` represented by this
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// `BasicCoverageBlock`).
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self.edge_from_bcbs.is_none() || counter_kind.is_expression(),
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"attempt to add a `Counter` to a BCB target with existing incoming edge counters"
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);
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let operand = counter_kind.as_operand();
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if let Some(replaced) = self.counter_kind.replace(counter_kind) {
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Error::from_string(format!(
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"attempt to set a BasicCoverageBlock coverage counter more than once; \
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{self:?} already had counter {replaced:?}",
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))
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} else {
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Ok(operand)
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}
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}
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|
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#[inline(always)]
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pub fn counter(&self) -> Option<&CoverageKind> {
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self.counter_kind.as_ref()
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}
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#[inline(always)]
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pub fn take_counter(&mut self) -> Option<CoverageKind> {
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self.counter_kind.take()
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}
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|
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pub fn set_edge_counter_from(
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&mut self,
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from_bcb: BasicCoverageBlock,
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counter_kind: CoverageKind,
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) -> Result<Operand, Error> {
|
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if level_enabled!(tracing::Level::DEBUG) {
|
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// If the BCB has an edge counter (to be injected into a new `BasicBlock`), it can also
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// have an expression (to be injected into an existing `BasicBlock` represented by this
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// `BasicCoverageBlock`).
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if self.counter_kind.as_ref().is_some_and(|c| !c.is_expression()) {
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return Error::from_string(format!(
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"attempt to add an incoming edge counter from {from_bcb:?} when the target BCB already \
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has a `Counter`"
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));
|
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}
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}
|
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let operand = counter_kind.as_operand();
|
|
if let Some(replaced) =
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self.edge_from_bcbs.get_or_insert_default().insert(from_bcb, counter_kind)
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{
|
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Error::from_string(format!(
|
|
"attempt to set an edge counter more than once; from_bcb: \
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{from_bcb:?} already had counter {replaced:?}",
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))
|
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} else {
|
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Ok(operand)
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}
|
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}
|
|
|
|
#[inline]
|
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pub fn edge_counter_from(&self, from_bcb: BasicCoverageBlock) -> Option<&CoverageKind> {
|
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if let Some(edge_from_bcbs) = &self.edge_from_bcbs {
|
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edge_from_bcbs.get(&from_bcb)
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} else {
|
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None
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|
}
|
|
}
|
|
|
|
#[inline]
|
|
pub fn take_edge_counters(
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&mut self,
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|
) -> Option<impl Iterator<Item = (BasicCoverageBlock, CoverageKind)>> {
|
|
self.edge_from_bcbs.take().map(|m| m.into_iter())
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|
}
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|
|
|
pub fn id(&self) -> String {
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|
format!("@{}", self.basic_blocks.iter().map(|bb| bb.index().to_string()).join(ID_SEPARATOR))
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|
}
|
|
}
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|
|
/// Represents a successor from a branching BasicCoverageBlock (such as the arms of a `SwitchInt`)
|
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/// as either the successor BCB itself, if it has only one incoming edge, or the successor _plus_
|
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/// the specific branching BCB, representing the edge between the two. The latter case
|
|
/// distinguishes this incoming edge from other incoming edges to the same `target_bcb`.
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|
#[derive(Clone, Copy, PartialEq, Eq)]
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|
pub(super) struct BcbBranch {
|
|
pub edge_from_bcb: Option<BasicCoverageBlock>,
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|
pub target_bcb: BasicCoverageBlock,
|
|
}
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|
|
|
impl BcbBranch {
|
|
pub fn from_to(
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|
from_bcb: BasicCoverageBlock,
|
|
to_bcb: BasicCoverageBlock,
|
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basic_coverage_blocks: &CoverageGraph,
|
|
) -> Self {
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|
let edge_from_bcb = if basic_coverage_blocks.predecessors[to_bcb].len() > 1 {
|
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Some(from_bcb)
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} else {
|
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None
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};
|
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Self { edge_from_bcb, target_bcb: to_bcb }
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}
|
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|
|
pub fn counter<'a>(
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&self,
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basic_coverage_blocks: &'a CoverageGraph,
|
|
) -> Option<&'a CoverageKind> {
|
|
if let Some(from_bcb) = self.edge_from_bcb {
|
|
basic_coverage_blocks[self.target_bcb].edge_counter_from(from_bcb)
|
|
} else {
|
|
basic_coverage_blocks[self.target_bcb].counter()
|
|
}
|
|
}
|
|
|
|
pub fn is_only_path_to_target(&self) -> bool {
|
|
self.edge_from_bcb.is_none()
|
|
}
|
|
}
|
|
|
|
impl std::fmt::Debug for BcbBranch {
|
|
fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
|
|
if let Some(from_bcb) = self.edge_from_bcb {
|
|
write!(fmt, "{:?}->{:?}", from_bcb, self.target_bcb)
|
|
} else {
|
|
write!(fmt, "{:?}", self.target_bcb)
|
|
}
|
|
}
|
|
}
|
|
|
|
// Returns the `Terminator`s non-unwind successors.
|
|
// FIXME(#78544): MIR InstrumentCoverage: Improve coverage of `#[should_panic]` tests and
|
|
// `catch_unwind()` handlers.
|
|
fn bcb_filtered_successors<'a, 'tcx>(
|
|
body: &'a mir::Body<'tcx>,
|
|
term_kind: &'a TerminatorKind<'tcx>,
|
|
) -> Box<dyn Iterator<Item = BasicBlock> + 'a> {
|
|
Box::new(
|
|
match &term_kind {
|
|
// SwitchInt successors are never unwind, and all of them should be traversed.
|
|
TerminatorKind::SwitchInt { ref targets, .. } => {
|
|
None.into_iter().chain(targets.all_targets().into_iter().copied())
|
|
}
|
|
// For all other kinds, return only the first successor, if any, and ignore unwinds.
|
|
// NOTE: `chain(&[])` is required to coerce the `option::iter` (from
|
|
// `next().into_iter()`) into the `mir::Successors` aliased type.
|
|
_ => term_kind.successors().next().into_iter().chain((&[]).into_iter().copied()),
|
|
}
|
|
.filter(move |&successor| body[successor].terminator().kind != TerminatorKind::Unreachable),
|
|
)
|
|
}
|
|
|
|
/// Maintains separate worklists for each loop in the BasicCoverageBlock CFG, plus one for the
|
|
/// CoverageGraph outside all loops. This supports traversing the BCB CFG in a way that
|
|
/// ensures a loop is completely traversed before processing Blocks after the end of the loop.
|
|
#[derive(Debug)]
|
|
pub(super) struct TraversalContext {
|
|
/// From one or more backedges returning to a loop header.
|
|
pub loop_backedges: Option<(Vec<BasicCoverageBlock>, BasicCoverageBlock)>,
|
|
|
|
/// worklist, to be traversed, of CoverageGraph in the loop with the given loop
|
|
/// backedges, such that the loop is the inner inner-most loop containing these
|
|
/// CoverageGraph
|
|
pub worklist: Vec<BasicCoverageBlock>,
|
|
}
|
|
|
|
pub(super) struct TraverseCoverageGraphWithLoops {
|
|
pub backedges: IndexVec<BasicCoverageBlock, Vec<BasicCoverageBlock>>,
|
|
pub context_stack: Vec<TraversalContext>,
|
|
visited: BitSet<BasicCoverageBlock>,
|
|
}
|
|
|
|
impl TraverseCoverageGraphWithLoops {
|
|
pub fn new(basic_coverage_blocks: &CoverageGraph) -> Self {
|
|
let start_bcb = basic_coverage_blocks.start_node();
|
|
let backedges = find_loop_backedges(basic_coverage_blocks);
|
|
let context_stack =
|
|
vec![TraversalContext { loop_backedges: None, worklist: vec![start_bcb] }];
|
|
// `context_stack` starts with a `TraversalContext` for the main function context (beginning
|
|
// with the `start` BasicCoverageBlock of the function). New worklists are pushed to the top
|
|
// of the stack as loops are entered, and popped off of the stack when a loop's worklist is
|
|
// exhausted.
|
|
let visited = BitSet::new_empty(basic_coverage_blocks.num_nodes());
|
|
Self { backedges, context_stack, visited }
|
|
}
|
|
|
|
pub fn next(&mut self, basic_coverage_blocks: &CoverageGraph) -> Option<BasicCoverageBlock> {
|
|
debug!(
|
|
"TraverseCoverageGraphWithLoops::next - context_stack: {:?}",
|
|
self.context_stack.iter().rev().collect::<Vec<_>>()
|
|
);
|
|
|
|
while let Some(context) = self.context_stack.last_mut() {
|
|
if let Some(next_bcb) = context.worklist.pop() {
|
|
if !self.visited.insert(next_bcb) {
|
|
debug!("Already visited: {:?}", next_bcb);
|
|
continue;
|
|
}
|
|
debug!("Visiting {:?}", next_bcb);
|
|
if self.backedges[next_bcb].len() > 0 {
|
|
debug!("{:?} is a loop header! Start a new TraversalContext...", next_bcb);
|
|
self.context_stack.push(TraversalContext {
|
|
loop_backedges: Some((self.backedges[next_bcb].clone(), next_bcb)),
|
|
worklist: Vec::new(),
|
|
});
|
|
}
|
|
self.extend_worklist(basic_coverage_blocks, next_bcb);
|
|
return Some(next_bcb);
|
|
} else {
|
|
// Strip contexts with empty worklists from the top of the stack
|
|
self.context_stack.pop();
|
|
}
|
|
}
|
|
|
|
None
|
|
}
|
|
|
|
pub fn extend_worklist(
|
|
&mut self,
|
|
basic_coverage_blocks: &CoverageGraph,
|
|
bcb: BasicCoverageBlock,
|
|
) {
|
|
let successors = &basic_coverage_blocks.successors[bcb];
|
|
debug!("{:?} has {} successors:", bcb, successors.len());
|
|
for &successor in successors {
|
|
if successor == bcb {
|
|
debug!(
|
|
"{:?} has itself as its own successor. (Note, the compiled code will \
|
|
generate an infinite loop.)",
|
|
bcb
|
|
);
|
|
// Don't re-add this successor to the worklist. We are already processing it.
|
|
break;
|
|
}
|
|
for context in self.context_stack.iter_mut().rev() {
|
|
// Add successors of the current BCB to the appropriate context. Successors that
|
|
// stay within a loop are added to the BCBs context worklist. Successors that
|
|
// exit the loop (they are not dominated by the loop header) must be reachable
|
|
// from other BCBs outside the loop, and they will be added to a different
|
|
// worklist.
|
|
//
|
|
// Branching blocks (with more than one successor) must be processed before
|
|
// blocks with only one successor, to prevent unnecessarily complicating
|
|
// `Expression`s by creating a Counter in a `BasicCoverageBlock` that the
|
|
// branching block would have given an `Expression` (or vice versa).
|
|
let (some_successor_to_add, some_loop_header) =
|
|
if let Some((_, loop_header)) = context.loop_backedges {
|
|
if basic_coverage_blocks.dominates(loop_header, successor) {
|
|
(Some(successor), Some(loop_header))
|
|
} else {
|
|
(None, None)
|
|
}
|
|
} else {
|
|
(Some(successor), None)
|
|
};
|
|
if let Some(successor_to_add) = some_successor_to_add {
|
|
if basic_coverage_blocks.successors[successor_to_add].len() > 1 {
|
|
debug!(
|
|
"{:?} successor is branching. Prioritize it at the beginning of \
|
|
the {}",
|
|
successor_to_add,
|
|
if let Some(loop_header) = some_loop_header {
|
|
format!("worklist for the loop headed by {loop_header:?}")
|
|
} else {
|
|
String::from("non-loop worklist")
|
|
},
|
|
);
|
|
context.worklist.insert(0, successor_to_add);
|
|
} else {
|
|
debug!(
|
|
"{:?} successor is non-branching. Defer it to the end of the {}",
|
|
successor_to_add,
|
|
if let Some(loop_header) = some_loop_header {
|
|
format!("worklist for the loop headed by {loop_header:?}")
|
|
} else {
|
|
String::from("non-loop worklist")
|
|
},
|
|
);
|
|
context.worklist.push(successor_to_add);
|
|
}
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
pub fn is_complete(&self) -> bool {
|
|
self.visited.count() == self.visited.domain_size()
|
|
}
|
|
|
|
pub fn unvisited(&self) -> Vec<BasicCoverageBlock> {
|
|
let mut unvisited_set: BitSet<BasicCoverageBlock> =
|
|
BitSet::new_filled(self.visited.domain_size());
|
|
unvisited_set.subtract(&self.visited);
|
|
unvisited_set.iter().collect::<Vec<_>>()
|
|
}
|
|
}
|
|
|
|
pub(super) fn find_loop_backedges(
|
|
basic_coverage_blocks: &CoverageGraph,
|
|
) -> IndexVec<BasicCoverageBlock, Vec<BasicCoverageBlock>> {
|
|
let num_bcbs = basic_coverage_blocks.num_nodes();
|
|
let mut backedges = IndexVec::from_elem_n(Vec::<BasicCoverageBlock>::new(), num_bcbs);
|
|
|
|
// Identify loops by their backedges.
|
|
for (bcb, _) in basic_coverage_blocks.iter_enumerated() {
|
|
for &successor in &basic_coverage_blocks.successors[bcb] {
|
|
if basic_coverage_blocks.dominates(successor, bcb) {
|
|
let loop_header = successor;
|
|
let backedge_from_bcb = bcb;
|
|
debug!(
|
|
"Found BCB backedge: {:?} -> loop_header: {:?}",
|
|
backedge_from_bcb, loop_header
|
|
);
|
|
backedges[loop_header].push(backedge_from_bcb);
|
|
}
|
|
}
|
|
}
|
|
backedges
|
|
}
|
|
|
|
pub struct ShortCircuitPreorder<
|
|
'a,
|
|
'tcx,
|
|
F: Fn(&'a mir::Body<'tcx>, &'a TerminatorKind<'tcx>) -> Box<dyn Iterator<Item = BasicBlock> + 'a>,
|
|
> {
|
|
body: &'a mir::Body<'tcx>,
|
|
visited: BitSet<BasicBlock>,
|
|
worklist: Vec<BasicBlock>,
|
|
filtered_successors: F,
|
|
}
|
|
|
|
impl<
|
|
'a,
|
|
'tcx,
|
|
F: Fn(&'a mir::Body<'tcx>, &'a TerminatorKind<'tcx>) -> Box<dyn Iterator<Item = BasicBlock> + 'a>,
|
|
> ShortCircuitPreorder<'a, 'tcx, F>
|
|
{
|
|
pub fn new(
|
|
body: &'a mir::Body<'tcx>,
|
|
filtered_successors: F,
|
|
) -> ShortCircuitPreorder<'a, 'tcx, F> {
|
|
let worklist = vec![mir::START_BLOCK];
|
|
|
|
ShortCircuitPreorder {
|
|
body,
|
|
visited: BitSet::new_empty(body.basic_blocks.len()),
|
|
worklist,
|
|
filtered_successors,
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<
|
|
'a,
|
|
'tcx,
|
|
F: Fn(&'a mir::Body<'tcx>, &'a TerminatorKind<'tcx>) -> Box<dyn Iterator<Item = BasicBlock> + 'a>,
|
|
> Iterator for ShortCircuitPreorder<'a, 'tcx, F>
|
|
{
|
|
type Item = (BasicBlock, &'a BasicBlockData<'tcx>);
|
|
|
|
fn next(&mut self) -> Option<(BasicBlock, &'a BasicBlockData<'tcx>)> {
|
|
while let Some(idx) = self.worklist.pop() {
|
|
if !self.visited.insert(idx) {
|
|
continue;
|
|
}
|
|
|
|
let data = &self.body[idx];
|
|
|
|
if let Some(ref term) = data.terminator {
|
|
self.worklist.extend((self.filtered_successors)(&self.body, &term.kind));
|
|
}
|
|
|
|
return Some((idx, data));
|
|
}
|
|
|
|
None
|
|
}
|
|
|
|
fn size_hint(&self) -> (usize, Option<usize>) {
|
|
let size = self.body.basic_blocks.len() - self.visited.count();
|
|
(size, Some(size))
|
|
}
|
|
}
|