mirror of
https://github.com/rust-lang/rust.git
synced 2025-10-24 22:17:08 +00:00
0510a1526d
coverage: Give the instrumentor its own counter type, separate from MIR Within the MIR representation of coverage data, `CoverageKind` is an important part of `StatementKind::Coverage`, but the `InstrumentCoverage` pass also uses it heavily as an internal data structure. This means that any change to `CoverageKind` also needs to update all of the internal parts of `InstrumentCoverage` that manipulate it directly, making the MIR representation difficult to modify. --- This change fixes that by giving the instrumentor its own `BcbCounter` type for internal use, which is then converted to a `CoverageKind` when injecting coverage information into MIR. The main change is mostly mechanical, because the initial `BcbCounter` is drop-in compatible with `CoverageKind`, minus the unnecessary `CoverageKind::Unreachable` variant. I've then removed the `function_source_hash` field from `BcbCounter::Counter`, as a small example of how the two types can now usefully differ from each other. Every counter in a MIR-level function should have the same source hash, so we can supply the hash during the conversion to `CoverageKind::Counter` instead. --- *Background:* BCB stands for “basic coverage block”, which is a node in the simplified control-flow graph used by coverage instrumentation. The instrumentor pass uses the function's actual MIR control-flow graph to build a simplified BCB graph, then assigns coverage counters and counter expressions to various nodes/edges in that simplified graph, and then finally injects corresponding coverage information into the underlying MIR.