Struct rustc_mir::transform::instrument_coverage::BasicCoverageBlock

struct BasicCoverageBlock {
    pub blocks: Vec<BasicBlock>,
}

A BasicCoverageBlock (BCB) represents the maximal-length sequence of CFG (MIR) BasicBlocks without conditional branches.

The BCB allows coverage analysis to be performed on a simplified projection of the underlying MIR CFG, without altering the original CFG. Note that running the MIR SimplifyCfg transform, is not sufficient, and therefore not necessary, since the BCB-based CFG projection is a more aggressive simplification. For example:

• The BCB CFG projection 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.
• 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 CoverageSpan will have no more than one Counter. In some cases, a BCB's execution count can be computed by CounterExpression. Additional disjoint CoverageSpans in a BCB can also be counted by CounterExpression (by adding ZERO to the BCB's primary counter or expression).

Dominator/dominated relationships (which are fundamental to the coverage analysis algorithm) between two BCBs can be computed using the mir::Body dominators() with any BasicBlock member of each BCB. (For consistency, BCB's use the first BasicBlock, also referred to as the bcb_leader_bb.)

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

Fields

blocks: Vec<BasicBlock>

Implementations

impl BasicCoverageBlock

pub fn leader_bb(&self) -> BasicBlock

pub fn id(&self) -> String

Trait Implementations

impl Clone for BasicCoverageBlock

fn clone(&self) -> BasicCoverageBlock

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for BasicCoverageBlock

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

Formats the value using the given formatter.