Struct BasicCoverageBlockData

pub(crate) struct BasicCoverageBlockData {
    pub(crate) basic_blocks: Vec<BasicBlock>,
    pub(crate) is_out_summable: bool,
}

BasicCoverageBlockData holds the data indexed by a BasicCoverageBlock.

A BasicCoverageBlock (BCB) represents the maximal-length sequence of MIR BasicBlocks without conditional branches, and form a new, simplified, coverage-specific Control Flow Graph, without altering the original MIR CFG.

Note that running the MIR SimplifyCfg transform is not sufficient (and therefore not necessary). The BCB-based CFG is a more aggressive simplification. For example:

• The BCB CFG ignores (trims) branches not relevant to coverage, such as unwind-related code, that is injected by the Rust compiler but has no physical source code to count. This also means a BasicBlock with a Call terminator can be merged into its primary successor target block, in the same BCB. (But, note: Issue #78544: “MIR InstrumentCoverage: Improve coverage of #[should_panic] tests and catch_unwind() handlers”)
• Some BasicBlock terminators support Rust-specific concerns–like borrow-checking–that are not relevant to coverage analysis. FalseUnwind, for example, can be treated the same as a Goto, and merged with its successor into the same BCB.

Each BCB with at least one computed coverage span will have no more than one Counter. In some cases, a BCB’s execution count can be computed by Expression. Additional disjoint coverage spans in a BCB can also be counted by Expression (by adding ZERO to the BCB’s primary counter or expression).

The BCB CFG is critical to simplifying the coverage analysis by ensuring graph path-based queries (dominates(), predecessors, successors, etc.) have branch (control flow) significance.

Fields

basic_blocks: Vec<BasicBlock>

is_out_summable: bool

If true, this node’s execution count can be assumed to be the sum of the execution counts of all of its out-edges (assuming no panics).

Notably, this is false for a node ending with TerminatorKind::Yield, because the yielding coroutine might not be resumed.

Implementations

impl BasicCoverageBlockData

pub(crate) fn leader_bb(&self) -> BasicBlock

pub(crate) fn last_bb(&self) -> BasicBlock

Trait Implementations

impl Clone for BasicCoverageBlockData

fn clone(&self) -> BasicCoverageBlockData

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for BasicCoverageBlockData

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

Layout

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 32 bytes