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coverage: Deal with unused functions and their names in one place

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This commit is contained in:
Zalathar
2025-03-21 15:14:22 +11:00
parent 75135aaf19
commit b3c40cf374
3 changed files with 51 additions and 39 deletions
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34
compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs
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@@ -73,12 +73,11 @@ pub(crate) fn finalize(cx: &CodegenCx<'_, '_>) {
// In a single designated CGU, also prepare covfun records for functions
// in this crate that were instrumented for coverage, but are unused.
if cx.codegen_unit.is_code_coverage_dead_code_cgu() {
let mut unused_instances = unused::gather_unused_function_instances(cx);
// Sort the unused instances by symbol name, for the same reason as the used ones.
unused_instances.sort_by_cached_key(|&instance| tcx.symbol_name(instance).name);
covfun_records.extend(unused_instances.into_iter().filter_map(|instance| {
prepare_covfun_record(tcx, &mut global_file_table, instance, false)
}));
unused::prepare_covfun_records_for_unused_functions(
cx,
&mut global_file_table,
&mut covfun_records,
);
}
// If there are no covfun records for this CGU, don't generate a covmap record.
@@ -97,33 +96,10 @@ pub(crate) fn finalize(cx: &CodegenCx<'_, '_>) {
// contain multiple covmap records from different compilation units.
let filenames_hash = llvm_cov::hash_bytes(&filenames_buffer);
let mut unused_function_names = vec![];
for covfun in &covfun_records {
unused_function_names.extend(covfun.mangled_function_name_if_unused());
covfun::generate_covfun_record(cx, filenames_hash, covfun)
}
// For unused functions, we need to take their mangled names and store them
// in a specially-named global array. LLVM's `InstrProfiling` pass will
// detect this global and include those names in its `__llvm_prf_names`
// section. (See `llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp`.)
if !unused_function_names.is_empty() {
assert!(cx.codegen_unit.is_code_coverage_dead_code_cgu());
let name_globals = unused_function_names
.into_iter()
.map(|mangled_function_name| cx.const_str(mangled_function_name).0)
.collect::<Vec<_>>();
let initializer = cx.const_array(cx.type_ptr(), &name_globals);
let array = llvm::add_global(cx.llmod, cx.val_ty(initializer), c"__llvm_coverage_names");
llvm::set_global_constant(array, true);
llvm::set_linkage(array, llvm::Linkage::InternalLinkage);
llvm::set_initializer(array, initializer);
}
// Generate the coverage map header, which contains the filenames used by
// this CGU's coverage mappings, and store it in a well-known global.
// (This is skipped if we returned early due to having no covfun records.)