bjoernager/rust
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coverage: Mappings for unused functions can all be zero

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There is no need to include a dummy counter reference in the coverage mappings
for an unused function.
This commit is contained in:
Zalathar 2023-09-07 19:58:11 +10:00
parent 2e5a9dd6c9
commit 59a11af1f9
10 changed files with 65 additions and 73 deletions
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14
compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs
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@ -89,9 +89,7 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
/// `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
/// them. Since the function is never called, all of its `CodeRegion`s can be
/// added as `unreachable_region`s.
fn define_unused_fn(&self, def_id: DefId) {
let instance = declare_unused_fn(self, def_id);
@ -227,14 +225,8 @@ fn add_unused_function_coverage<'tcx>(
let tcx = cx.tcx;
let mut function_coverage = FunctionCoverage::unused(tcx, instance);
for (index, &code_region) in tcx.covered_code_regions(def_id).iter().enumerate() {
if index == 0 {
// Insert at least one real counter so the LLVM CoverageMappingReader will find expected
// definitions.
function_coverage.add_counter(UNUSED_FUNCTION_COUNTER_ID, code_region.clone());
} else {
function_coverage.add_unreachable_region(code_region.clone());
}
for &code_region in tcx.covered_code_regions(def_id) {
function_coverage.add_unreachable_region(code_region.clone());
}
if let Some(coverage_context) = cx.coverage_context() {