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This commit is contained in:
Rich Kadel 2021-03-23 14:25:52 -07:00
parent 94a3454b03
commit 0859cec652
3 changed files with 33 additions and 26 deletions
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19
compiler/rustc_codegen_ssa/src/traits/coverageinfo.rs
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@ -6,22 +6,11 @@ use rustc_middle::ty::Instance;
pub trait CoverageInfoMethods<'tcx>: BackendTypes {
fn coverageinfo_finalize(&self);
/// Functions with MIR-based coverage are normally codegenned _only_ if
/// called. LLVM coverage tools typically expect every function to be
/// defined (even if unused), with at least one call to LLVM intrinsic
/// `instrprof.increment`.
///
/// Codegen a small function that will never be called, with one counter
/// that will never be incremented.
///
/// For used/called functions, the coverageinfo was already added to the
/// `function_coverage_map` (keyed by function `Instance`) during codegen.
/// But in this case, since the unused function was _not_ previously
/// codegenned, collect the coverage `CodeRegion`s from the MIR and add
/// them. The first `CodeRegion` is used to add a single counter, with the
/// same counter ID used in the injected `instrprof.increment` intrinsic
/// call. Since the function is never called, all other `CodeRegion`s can be
/// added as `unreachable_region`s.
/// that will never be incremented, that gives LLVM coverage tools a
/// function definition it needs in order to resolve coverage map references
/// to unused functions. This is necessary so unused functions will appear
/// as uncovered (coverage execution count `0`) in LLVM coverage reports.
fn define_unused_fn(&self, def_id: DefId);
/// For LLVM codegen, returns a function-specific `Value` for a global