diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs index 9a2473d6cf23d..5e62ce285dd8c 100644 --- a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs +++ b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs @@ -5,15 +5,11 @@ use rustc_abi::Align; use rustc_codegen_ssa::traits::{ BaseTypeCodegenMethods, ConstCodegenMethods, StaticCodegenMethods, }; -use rustc_data_structures::fx::{FxHashSet, FxIndexMap}; -use rustc_hir::def_id::{DefId, LocalDefId}; +use rustc_data_structures::fx::FxIndexMap; use rustc_index::IndexVec; -use rustc_middle::mir; -use rustc_middle::mir::mono::MonoItemPartitions; -use rustc_middle::ty::{self, TyCtxt}; +use rustc_middle::ty::TyCtxt; use rustc_session::RemapFileNameExt; use rustc_session::config::RemapPathScopeComponents; -use rustc_span::def_id::DefIdSet; use rustc_span::{SourceFile, StableSourceFileId}; use tracing::debug; @@ -24,6 +20,7 @@ use crate::llvm; mod covfun; mod spans; +mod unused; /// Generates and exports the coverage map, which is embedded in special /// linker sections in the final binary. @@ -76,12 +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 = 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. @@ -100,33 +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::>(); - 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.) @@ -249,121 +222,3 @@ fn generate_covmap_record<'ll>(cx: &CodegenCx<'ll, '_>, version: u32, filenames_ cx.add_used_global(covmap_global); } - -/// Each CGU will normally only emit coverage metadata for the functions that it actually generates. -/// But since we don't want unused functions to disappear from coverage reports, we also scan for -/// functions that were instrumented but are not participating in codegen. -/// -/// These unused functions don't need to be codegenned, but we do need to add them to the function -/// coverage map (in a single designated CGU) so that we still emit coverage mappings for them. -/// We also end up adding their symbol names to a special global array that LLVM will include in -/// its embedded coverage data. -fn gather_unused_function_instances<'tcx>(cx: &CodegenCx<'_, 'tcx>) -> Vec> { - assert!(cx.codegen_unit.is_code_coverage_dead_code_cgu()); - - let tcx = cx.tcx; - let usage = prepare_usage_sets(tcx); - - let is_unused_fn = |def_id: LocalDefId| -> bool { - // Usage sets expect `DefId`, so convert from `LocalDefId`. - let d: DefId = LocalDefId::to_def_id(def_id); - // To be potentially eligible for "unused function" mappings, a definition must: - // - Be eligible for coverage instrumentation - // - Not participate directly in codegen (or have lost all its coverage statements) - // - Not have any coverage statements inlined into codegenned functions - tcx.is_eligible_for_coverage(def_id) - && (!usage.all_mono_items.contains(&d) || usage.missing_own_coverage.contains(&d)) - && !usage.used_via_inlining.contains(&d) - }; - - // FIXME(#79651): Consider trying to filter out dummy instantiations of - // unused generic functions from library crates, because they can produce - // "unused instantiation" in coverage reports even when they are actually - // used by some downstream crate in the same binary. - - tcx.mir_keys(()) - .iter() - .copied() - .filter(|&def_id| is_unused_fn(def_id)) - .map(|def_id| make_dummy_instance(tcx, def_id)) - .collect::>() -} - -struct UsageSets<'tcx> { - all_mono_items: &'tcx DefIdSet, - used_via_inlining: FxHashSet, - missing_own_coverage: FxHashSet, -} - -/// Prepare sets of definitions that are relevant to deciding whether something -/// is an "unused function" for coverage purposes. -fn prepare_usage_sets<'tcx>(tcx: TyCtxt<'tcx>) -> UsageSets<'tcx> { - let MonoItemPartitions { all_mono_items, codegen_units, .. } = - tcx.collect_and_partition_mono_items(()); - - // Obtain a MIR body for each function participating in codegen, via an - // arbitrary instance. - let mut def_ids_seen = FxHashSet::default(); - let def_and_mir_for_all_mono_fns = codegen_units - .iter() - .flat_map(|cgu| cgu.items().keys()) - .filter_map(|item| match item { - mir::mono::MonoItem::Fn(instance) => Some(instance), - mir::mono::MonoItem::Static(_) | mir::mono::MonoItem::GlobalAsm(_) => None, - }) - // We only need one arbitrary instance per definition. - .filter(move |instance| def_ids_seen.insert(instance.def_id())) - .map(|instance| { - // We don't care about the instance, just its underlying MIR. - let body = tcx.instance_mir(instance.def); - (instance.def_id(), body) - }); - - // Functions whose coverage statements were found inlined into other functions. - let mut used_via_inlining = FxHashSet::default(); - // Functions that were instrumented, but had all of their coverage statements - // removed by later MIR transforms (e.g. UnreachablePropagation). - let mut missing_own_coverage = FxHashSet::default(); - - for (def_id, body) in def_and_mir_for_all_mono_fns { - let mut saw_own_coverage = false; - - // Inspect every coverage statement in the function's MIR. - for stmt in body - .basic_blocks - .iter() - .flat_map(|block| &block.statements) - .filter(|stmt| matches!(stmt.kind, mir::StatementKind::Coverage(_))) - { - if let Some(inlined) = stmt.source_info.scope.inlined_instance(&body.source_scopes) { - // This coverage statement was inlined from another function. - used_via_inlining.insert(inlined.def_id()); - } else { - // Non-inlined coverage statements belong to the enclosing function. - saw_own_coverage = true; - } - } - - if !saw_own_coverage && body.function_coverage_info.is_some() { - missing_own_coverage.insert(def_id); - } - } - - UsageSets { all_mono_items, used_via_inlining, missing_own_coverage } -} - -fn make_dummy_instance<'tcx>(tcx: TyCtxt<'tcx>, local_def_id: LocalDefId) -> ty::Instance<'tcx> { - let def_id = local_def_id.to_def_id(); - - // Make a dummy instance that fills in all generics with placeholders. - ty::Instance::new( - def_id, - ty::GenericArgs::for_item(tcx, def_id, |param, _| { - if let ty::GenericParamDefKind::Lifetime = param.kind { - tcx.lifetimes.re_erased.into() - } else { - tcx.mk_param_from_def(param) - } - }), - ) -} diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/covfun.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/covfun.rs index 048e1988c3278..93419c2caad25 100644 --- a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/covfun.rs +++ b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/covfun.rs @@ -37,14 +37,6 @@ pub(crate) struct CovfunRecord<'tcx> { regions: ffi::Regions, } -impl<'tcx> CovfunRecord<'tcx> { - /// FIXME(Zalathar): Make this the responsibility of the code that determines - /// which functions are unused. - pub(crate) fn mangled_function_name_if_unused(&self) -> Option<&'tcx str> { - (!self.is_used).then_some(self.mangled_function_name) - } -} - pub(crate) fn prepare_covfun_record<'tcx>( tcx: TyCtxt<'tcx>, global_file_table: &mut GlobalFileTable, diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/unused.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/unused.rs new file mode 100644 index 0000000000000..ab030f5b6152a --- /dev/null +++ b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/unused.rs @@ -0,0 +1,172 @@ +use rustc_codegen_ssa::traits::{BaseTypeCodegenMethods, ConstCodegenMethods}; +use rustc_data_structures::fx::FxHashSet; +use rustc_hir::def_id::{DefId, LocalDefId}; +use rustc_middle::mir; +use rustc_middle::mir::mono::MonoItemPartitions; +use rustc_middle::ty::{self, TyCtxt}; +use rustc_span::def_id::DefIdSet; + +use crate::common::CodegenCx; +use crate::coverageinfo::mapgen::GlobalFileTable; +use crate::coverageinfo::mapgen::covfun::{CovfunRecord, prepare_covfun_record}; +use crate::llvm; + +/// Each CGU will normally only emit coverage metadata for the functions that it actually generates. +/// But since we don't want unused functions to disappear from coverage reports, we also scan for +/// functions that were instrumented but are not participating in codegen. +/// +/// These unused functions don't need to be codegenned, but we do need to add them to the function +/// coverage map (in a single designated CGU) so that we still emit coverage mappings for them. +/// We also end up adding their symbol names to a special global array that LLVM will include in +/// its embedded coverage data. +pub(crate) fn prepare_covfun_records_for_unused_functions<'tcx>( + cx: &CodegenCx<'_, 'tcx>, + global_file_table: &mut GlobalFileTable, + covfun_records: &mut Vec>, +) { + assert!(cx.codegen_unit.is_code_coverage_dead_code_cgu()); + + let mut unused_instances = gather_unused_function_instances(cx); + // Sort the unused instances by symbol name, so that their order isn't hash-sensitive. + unused_instances.sort_by_key(|instance| instance.symbol_name); + + // Try to create a covfun record for each unused function. + let mut name_globals = Vec::with_capacity(unused_instances.len()); + covfun_records.extend(unused_instances.into_iter().filter_map(|unused| try { + let record = prepare_covfun_record(cx.tcx, global_file_table, unused.instance, false)?; + // If successful, also store its symbol name in a global constant. + name_globals.push(cx.const_str(unused.symbol_name.name).0); + record + })); + + // Store the names of unused functions in a specially-named global array. + // LLVM's `InstrProfilling` pass will detect this array, and include the + // referenced names in its `__llvm_prf_names` section. + // (See `llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp`.) + if !name_globals.is_empty() { + 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); + } +} + +/// Holds a dummy function instance along with its symbol name, to avoid having +/// to repeatedly query for the name. +struct UnusedInstance<'tcx> { + instance: ty::Instance<'tcx>, + symbol_name: ty::SymbolName<'tcx>, +} + +fn gather_unused_function_instances<'tcx>(cx: &CodegenCx<'_, 'tcx>) -> Vec> { + assert!(cx.codegen_unit.is_code_coverage_dead_code_cgu()); + + let tcx = cx.tcx; + let usage = prepare_usage_sets(tcx); + + let is_unused_fn = |def_id: LocalDefId| -> bool { + // Usage sets expect `DefId`, so convert from `LocalDefId`. + let d: DefId = LocalDefId::to_def_id(def_id); + // To be potentially eligible for "unused function" mappings, a definition must: + // - Be eligible for coverage instrumentation + // - Not participate directly in codegen (or have lost all its coverage statements) + // - Not have any coverage statements inlined into codegenned functions + tcx.is_eligible_for_coverage(def_id) + && (!usage.all_mono_items.contains(&d) || usage.missing_own_coverage.contains(&d)) + && !usage.used_via_inlining.contains(&d) + }; + + // FIXME(#79651): Consider trying to filter out dummy instantiations of + // unused generic functions from library crates, because they can produce + // "unused instantiation" in coverage reports even when they are actually + // used by some downstream crate in the same binary. + + tcx.mir_keys(()) + .iter() + .copied() + .filter(|&def_id| is_unused_fn(def_id)) + .map(|def_id| make_dummy_instance(tcx, def_id)) + .map(|instance| UnusedInstance { instance, symbol_name: tcx.symbol_name(instance) }) + .collect::>() +} + +struct UsageSets<'tcx> { + all_mono_items: &'tcx DefIdSet, + used_via_inlining: FxHashSet, + missing_own_coverage: FxHashSet, +} + +/// Prepare sets of definitions that are relevant to deciding whether something +/// is an "unused function" for coverage purposes. +fn prepare_usage_sets<'tcx>(tcx: TyCtxt<'tcx>) -> UsageSets<'tcx> { + let MonoItemPartitions { all_mono_items, codegen_units, .. } = + tcx.collect_and_partition_mono_items(()); + + // Obtain a MIR body for each function participating in codegen, via an + // arbitrary instance. + let mut def_ids_seen = FxHashSet::default(); + let def_and_mir_for_all_mono_fns = codegen_units + .iter() + .flat_map(|cgu| cgu.items().keys()) + .filter_map(|item| match item { + mir::mono::MonoItem::Fn(instance) => Some(instance), + mir::mono::MonoItem::Static(_) | mir::mono::MonoItem::GlobalAsm(_) => None, + }) + // We only need one arbitrary instance per definition. + .filter(move |instance| def_ids_seen.insert(instance.def_id())) + .map(|instance| { + // We don't care about the instance, just its underlying MIR. + let body = tcx.instance_mir(instance.def); + (instance.def_id(), body) + }); + + // Functions whose coverage statements were found inlined into other functions. + let mut used_via_inlining = FxHashSet::default(); + // Functions that were instrumented, but had all of their coverage statements + // removed by later MIR transforms (e.g. UnreachablePropagation). + let mut missing_own_coverage = FxHashSet::default(); + + for (def_id, body) in def_and_mir_for_all_mono_fns { + let mut saw_own_coverage = false; + + // Inspect every coverage statement in the function's MIR. + for stmt in body + .basic_blocks + .iter() + .flat_map(|block| &block.statements) + .filter(|stmt| matches!(stmt.kind, mir::StatementKind::Coverage(_))) + { + if let Some(inlined) = stmt.source_info.scope.inlined_instance(&body.source_scopes) { + // This coverage statement was inlined from another function. + used_via_inlining.insert(inlined.def_id()); + } else { + // Non-inlined coverage statements belong to the enclosing function. + saw_own_coverage = true; + } + } + + if !saw_own_coverage && body.function_coverage_info.is_some() { + missing_own_coverage.insert(def_id); + } + } + + UsageSets { all_mono_items, used_via_inlining, missing_own_coverage } +} + +fn make_dummy_instance<'tcx>(tcx: TyCtxt<'tcx>, local_def_id: LocalDefId) -> ty::Instance<'tcx> { + let def_id = local_def_id.to_def_id(); + + // Make a dummy instance that fills in all generics with placeholders. + ty::Instance::new( + def_id, + ty::GenericArgs::for_item(tcx, def_id, |param, _| { + if let ty::GenericParamDefKind::Lifetime = param.kind { + tcx.lifetimes.re_erased.into() + } else { + tcx.mk_param_from_def(param) + } + }), + ) +}