diff options
Diffstat (limited to 'compiler/rustc_codegen_llvm/src')
| -rw-r--r-- | compiler/rustc_codegen_llvm/src/base.rs | 2 | ||||
| -rw-r--r-- | compiler/rustc_codegen_llvm/src/context.rs | 8 | ||||
| -rw-r--r-- | compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs | 228 | ||||
| -rw-r--r-- | compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs | 141 |
4 files changed, 231 insertions, 148 deletions
diff --git a/compiler/rustc_codegen_llvm/src/base.rs b/compiler/rustc_codegen_llvm/src/base.rs index d5be3132dee..db8abdd9b13 100644 --- a/compiler/rustc_codegen_llvm/src/base.rs +++ b/compiler/rustc_codegen_llvm/src/base.rs @@ -143,7 +143,7 @@ pub fn compile_codegen_unit( // Finalize code coverage by injecting the coverage map. Note, the coverage map will // also be added to the `llvm.used` variable, created next. - if cx.sess().opts.debugging_opts.instrument_coverage { + if cx.sess().instrument_coverage() { cx.coverageinfo_finalize(); } diff --git a/compiler/rustc_codegen_llvm/src/context.rs b/compiler/rustc_codegen_llvm/src/context.rs index 21473f3b114..4d0498ac783 100644 --- a/compiler/rustc_codegen_llvm/src/context.rs +++ b/compiler/rustc_codegen_llvm/src/context.rs @@ -79,7 +79,7 @@ pub struct CodegenCx<'ll, 'tcx> { pub pointee_infos: RefCell<FxHashMap<(Ty<'tcx>, Size), Option<PointeeInfo>>>, pub isize_ty: &'ll Type, - pub coverage_cx: Option<coverageinfo::CrateCoverageContext<'tcx>>, + pub coverage_cx: Option<coverageinfo::CrateCoverageContext<'ll, 'tcx>>, pub dbg_cx: Option<debuginfo::CrateDebugContext<'ll, 'tcx>>, eh_personality: Cell<Option<&'ll Value>>, @@ -280,7 +280,7 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> { let (llcx, llmod) = (&*llvm_module.llcx, llvm_module.llmod()); - let coverage_cx = if tcx.sess.opts.debugging_opts.instrument_coverage { + let coverage_cx = if tcx.sess.instrument_coverage() { let covctx = coverageinfo::CrateCoverageContext::new(); Some(covctx) } else { @@ -331,7 +331,7 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> { } #[inline] - pub fn coverage_context(&'a self) -> Option<&'a coverageinfo::CrateCoverageContext<'tcx>> { + pub fn coverage_context(&'a self) -> Option<&'a coverageinfo::CrateCoverageContext<'ll, 'tcx>> { self.coverage_cx.as_ref() } } @@ -712,7 +712,7 @@ impl CodegenCx<'b, 'tcx> { ifn!("llvm.va_end", fn(i8p) -> void); ifn!("llvm.va_copy", fn(i8p, i8p) -> void); - if self.sess().opts.debugging_opts.instrument_coverage { + if self.sess().instrument_coverage() { ifn!("llvm.instrprof.increment", fn(i8p, t_i64, t_i32, t_i32) -> void); } diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs index 352638aa88e..239f786a727 100644 --- a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs +++ b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs @@ -3,13 +3,12 @@ use crate::coverageinfo; use crate::llvm; use llvm::coverageinfo::CounterMappingRegion; -use rustc_codegen_ssa::coverageinfo::map::{Counter, CounterExpression, FunctionCoverage}; -use rustc_codegen_ssa::traits::ConstMethods; +use rustc_codegen_ssa::coverageinfo::map::{Counter, CounterExpression}; +use rustc_codegen_ssa::traits::{ConstMethods, CoverageInfoMethods}; use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet}; use rustc_hir::def_id::{DefId, DefIdSet, LOCAL_CRATE}; use rustc_llvm::RustString; use rustc_middle::mir::coverage::CodeRegion; -use rustc_middle::ty::{Instance, TyCtxt}; use rustc_span::Symbol; use std::ffi::CString; @@ -20,16 +19,17 @@ use tracing::debug; /// /// This Coverage Map complies with Coverage Mapping Format version 4 (zero-based encoded as 3), /// as defined at [LLVM Code Coverage Mapping Format](https://github.com/rust-lang/llvm-project/blob/rustc/11.0-2020-10-12/llvm/docs/CoverageMappingFormat.rst#llvm-code-coverage-mapping-format) -/// and published in Rust's current (November 2020) fork of LLVM. This version is supported by the -/// LLVM coverage tools (`llvm-profdata` and `llvm-cov`) bundled with Rust's fork of LLVM. +/// and published in Rust's November 2020 fork of LLVM. This version is supported by the LLVM +/// coverage tools (`llvm-profdata` and `llvm-cov`) bundled with Rust's fork of LLVM. /// /// Consequently, Rust's bundled version of Clang also generates Coverage Maps compliant with -/// version 3. Clang's implementation of Coverage Map generation was referenced when implementing -/// this Rust version, and though the format documentation is very explicit and detailed, some -/// undocumented details in Clang's implementation (that may or may not be important) were also -/// replicated for Rust's Coverage Map. +/// the same version. Clang's implementation of Coverage Map generation was referenced when +/// implementing this Rust version, and though the format documentation is very explicit and +/// detailed, some undocumented details in Clang's implementation (that may or may not be important) +/// were also replicated for Rust's Coverage Map. pub fn finalize<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>) { let tcx = cx.tcx; + // Ensure LLVM supports Coverage Map Version 4 (encoded as a zero-based value: 3). // If not, the LLVM Version must be less than 11. let version = coverageinfo::mapping_version(); @@ -39,17 +39,24 @@ pub fn finalize<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>) { debug!("Generating coverage map for CodegenUnit: `{}`", cx.codegen_unit.name()); - let mut function_coverage_map = match cx.coverage_context() { + // In order to show that unused functions have coverage counts of zero (0), LLVM requires the + // functions exist. Generate synthetic functions with a (required) single counter, and add the + // MIR `Coverage` code regions to the `function_coverage_map`, before calling + // `ctx.take_function_coverage_map()`. + if !tcx.sess.instrument_coverage_except_unused_functions() { + add_unused_functions(cx); + } + + let function_coverage_map = match cx.coverage_context() { Some(ctx) => ctx.take_function_coverage_map(), None => return, }; + if function_coverage_map.is_empty() { // This module has no functions with coverage instrumentation return; } - add_unreachable_coverage(tcx, &mut function_coverage_map); - let mut mapgen = CoverageMapGenerator::new(); // Encode coverage mappings and generate function records @@ -57,7 +64,8 @@ pub fn finalize<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>) { for (instance, function_coverage) in function_coverage_map { debug!("Generate function coverage for {}, {:?}", cx.codegen_unit.name(), instance); let mangled_function_name = tcx.symbol_name(instance).to_string(); - let function_source_hash = function_coverage.source_hash(); + let source_hash = function_coverage.source_hash(); + let is_used = function_coverage.is_used(); let (expressions, counter_regions) = function_coverage.get_expressions_and_counter_regions(); @@ -69,7 +77,7 @@ pub fn finalize<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>) { "Every `FunctionCoverage` should have at least one counter" ); - function_data.push((mangled_function_name, function_source_hash, coverage_mapping_buffer)); + function_data.push((mangled_function_name, source_hash, is_used, coverage_mapping_buffer)); } // Encode all filenames referenced by counters/expressions in this module @@ -84,13 +92,14 @@ pub fn finalize<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>) { // Generate the LLVM IR representation of the coverage map and store it in a well-known global let cov_data_val = mapgen.generate_coverage_map(cx, version, filenames_size, filenames_val); - for (mangled_function_name, function_source_hash, coverage_mapping_buffer) in function_data { + for (mangled_function_name, source_hash, is_used, coverage_mapping_buffer) in function_data { save_function_record( cx, mangled_function_name, - function_source_hash, + source_hash, filenames_ref, coverage_mapping_buffer, + is_used, ); } @@ -201,9 +210,10 @@ impl CoverageMapGenerator { fn save_function_record( cx: &CodegenCx<'ll, 'tcx>, mangled_function_name: String, - function_source_hash: u64, + source_hash: u64, filenames_ref: u64, coverage_mapping_buffer: Vec<u8>, + is_used: bool, ) { // Concatenate the encoded coverage mappings let coverage_mapping_size = coverage_mapping_buffer.len(); @@ -212,128 +222,120 @@ fn save_function_record( let func_name_hash = coverageinfo::hash_str(&mangled_function_name); let func_name_hash_val = cx.const_u64(func_name_hash); let coverage_mapping_size_val = cx.const_u32(coverage_mapping_size as u32); - let func_hash_val = cx.const_u64(function_source_hash); + let source_hash_val = cx.const_u64(source_hash); let filenames_ref_val = cx.const_u64(filenames_ref); let func_record_val = cx.const_struct( &[ func_name_hash_val, coverage_mapping_size_val, - func_hash_val, + source_hash_val, filenames_ref_val, coverage_mapping_val, ], /*packed=*/ true, ); - // At the present time, the coverage map for Rust assumes every instrumented function `is_used`. - // Note that Clang marks functions as "unused" in `CodeGenPGO::emitEmptyCounterMapping`. (See: - // https://github.com/rust-lang/llvm-project/blob/de02a75e398415bad4df27b4547c25b896c8bf3b/clang%2Flib%2FCodeGen%2FCodeGenPGO.cpp#L877-L878 - // for example.) - // - // It's not yet clear if or how this may be applied to Rust in the future, but the `is_used` - // argument is available and handled similarly. - let is_used = true; coverageinfo::save_func_record_to_mod(cx, func_name_hash, func_record_val, is_used); } /// When finalizing the coverage map, `FunctionCoverage` only has the `CodeRegion`s and counters for /// the functions that went through codegen; such as public functions and "used" functions /// (functions referenced by other "used" or public items). Any other functions considered unused, -/// or "Unreachable" were still parsed and processed through the MIR stage. +/// or "Unreachable", were still parsed and processed through the MIR stage, but were not +/// codegenned. (Note that `-Clink-dead-code` can force some unused code to be codegenned, but +/// that flag is known to cause other errors, when combined with `-Z instrument-coverage`; and +/// `-Clink-dead-code` will not generate code for unused generic functions.) /// -/// We can find the unreachable functions by the set difference of all MIR `DefId`s (`tcx` query -/// `mir_keys`) minus the codegenned `DefId`s (`tcx` query `collect_and_partition_mono_items`). +/// We can find the unused functions (including generic functions) by the set difference of all MIR +/// `DefId`s (`tcx` query `mir_keys`) minus the codegenned `DefId`s (`tcx` query +/// `collect_and_partition_mono_items`). /// /// *HOWEVER* the codegenned `DefId`s are partitioned across multiple `CodegenUnit`s (CGUs), and /// this function is processing a `function_coverage_map` for the functions (`Instance`/`DefId`) -/// allocated to only one of those CGUs. We must NOT inject any "Unreachable" functions's -/// `CodeRegion`s more than once, so we have to pick which CGU's `function_coverage_map` to add -/// each "Unreachable" function to. -/// -/// Some constraints: -/// -/// 1. The file name of an "Unreachable" function must match the file name of the existing -/// codegenned (covered) function to which the unreachable code regions will be added. -/// 2. The function to which the unreachable code regions will be added must not be a generic -/// function (must not have type parameters) because the coverage tools will get confused -/// if the codegenned function has more than one instantiation and additional `CodeRegion`s -/// attached to only one of those instantiations. -fn add_unreachable_coverage<'tcx>( - tcx: TyCtxt<'tcx>, - function_coverage_map: &mut FxHashMap<Instance<'tcx>, FunctionCoverage<'tcx>>, -) { +/// allocated to only one of those CGUs. We must NOT inject any unused functions's `CodeRegion`s +/// more than once, so we have to pick a CGUs `function_coverage_map` into which the unused +/// function will be inserted. +fn add_unused_functions<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>) { + let tcx = cx.tcx; + // FIXME(#79622): Can this solution be simplified and/or improved? Are there other sources // of compiler state data that might help (or better sources that could be exposed, but // aren't yet)? - // Note: If the crate *only* defines generic functions, there are no codegenerated non-generic - // functions to add any unreachable code to. In this case, the unreachable code regions will - // have no coverage, instead of having coverage with zero executions. - // - // This is probably still an improvement over Clang, which does not generate any coverage - // for uninstantiated template functions. - - let has_non_generic_def_ids = - function_coverage_map.keys().any(|instance| instance.def.attrs(tcx).len() == 0); - - if !has_non_generic_def_ids { - // There are no non-generic functions to add unreachable `CodeRegion`s to - return; - } + let ignore_unused_generics = tcx.sess.instrument_coverage_except_unused_generics(); - let all_def_ids: DefIdSet = - tcx.mir_keys(LOCAL_CRATE).iter().map(|local_def_id| local_def_id.to_def_id()).collect(); + let all_def_ids: DefIdSet = tcx + .mir_keys(LOCAL_CRATE) + .iter() + .filter_map(|local_def_id| { + let def_id = local_def_id.to_def_id(); + if ignore_unused_generics && tcx.generics_of(def_id).count() > 0 { + return None; + } + Some(local_def_id.to_def_id()) + }) + .collect(); let codegenned_def_ids = tcx.codegened_and_inlined_items(LOCAL_CRATE); - let mut unreachable_def_ids_by_file: FxHashMap<Symbol, Vec<DefId>> = FxHashMap::default(); + let mut unused_def_ids_by_file: FxHashMap<Symbol, Vec<DefId>> = FxHashMap::default(); for &non_codegenned_def_id in all_def_ids.difference(codegenned_def_ids) { - // Make sure the non-codegenned (unreachable) function has a file_name + // Make sure the non-codegenned (unused) function has a file_name if let Some(non_codegenned_file_name) = tcx.covered_file_name(non_codegenned_def_id) { - let def_ids = unreachable_def_ids_by_file - .entry(*non_codegenned_file_name) - .or_insert_with(Vec::new); + let def_ids = + unused_def_ids_by_file.entry(*non_codegenned_file_name).or_insert_with(Vec::new); def_ids.push(non_codegenned_def_id); } } - if unreachable_def_ids_by_file.is_empty() { - // There are no unreachable functions with file names to add (in any CGU) + if unused_def_ids_by_file.is_empty() { + // There are no unused functions with file names to add (in any CGU) return; } - // Since there may be multiple `CodegenUnit`s, some codegenned_def_ids may be codegenned in a - // different CGU, and will be added to the function_coverage_map for each CGU. Determine which - // function_coverage_map has the responsibility for publishing unreachable coverage - // based on file name: + // Each `CodegenUnit` (CGU) has its own function_coverage_map, and generates a specific binary + // with its own coverage map. + // + // Each covered function `Instance` can be included in only one coverage map, produced from a + // specific function_coverage_map, from a specific CGU. // - // For each covered file name, sort ONLY the non-generic codegenned_def_ids, and if - // covered_def_ids.contains(the first def_id) for a given file_name, add the unreachable code - // region in this function_coverage_map. Otherwise, ignore it and assume another CGU's - // function_coverage_map will be adding it (because it will be first for one, and only one, - // of them). + // Since unused functions did not generate code, they are not associated with any CGU yet. + // + // To avoid injecting the unused functions in multiple coverage maps (for multiple CGUs) + // determine which function_coverage_map has the responsibility for publishing unreachable + // coverage, based on file name: For each unused function, find the CGU that generates the + // first function (based on sorted `DefId`) from the same file. + // + // Add a new `FunctionCoverage` to the `function_coverage_map`, with unreachable code regions + // for each region in it's MIR. + + // Convert the `HashSet` of `codegenned_def_ids` to a sortable vector, and sort them. let mut sorted_codegenned_def_ids: Vec<DefId> = codegenned_def_ids.iter().map(|def_id| *def_id).collect(); sorted_codegenned_def_ids.sort_unstable(); let mut first_covered_def_id_by_file: FxHashMap<Symbol, DefId> = FxHashMap::default(); for &def_id in sorted_codegenned_def_ids.iter() { - // Only consider non-generic functions, to potentially add unreachable code regions - if tcx.generics_of(def_id).count() == 0 { - if let Some(covered_file_name) = tcx.covered_file_name(def_id) { - // Only add files known to have unreachable functions - if unreachable_def_ids_by_file.contains_key(covered_file_name) { - first_covered_def_id_by_file.entry(*covered_file_name).or_insert(def_id); - } + if let Some(covered_file_name) = tcx.covered_file_name(def_id) { + // Only add files known to have unused functions + if unused_def_ids_by_file.contains_key(covered_file_name) { + first_covered_def_id_by_file.entry(*covered_file_name).or_insert(def_id); } } } // Get the set of def_ids with coverage regions, known by *this* CoverageContext. - let cgu_covered_def_ids: DefIdSet = - function_coverage_map.keys().map(|instance| instance.def.def_id()).collect(); + let cgu_covered_def_ids: DefIdSet = match cx.coverage_context() { + Some(ctx) => ctx + .function_coverage_map + .borrow() + .keys() + .map(|&instance| instance.def.def_id()) + .collect(), + None => return, + }; - let mut cgu_covered_files: FxHashSet<Symbol> = first_covered_def_id_by_file + let cgu_covered_files: FxHashSet<Symbol> = first_covered_def_id_by_file .iter() .filter_map( |(&file_name, def_id)| { @@ -342,49 +344,13 @@ fn add_unreachable_coverage<'tcx>( ) .collect(); - // Find the first covered, non-generic function (instance) for each cgu_covered_file. Take the - // unreachable code regions for that file, and add them to the function. - // - // There are three `for` loops here, but (a) the lists have already been reduced to the minimum - // required values, the lists are further reduced (by `remove()` calls) when elements are no - // longer needed, and there are several opportunities to branch out of loops early. - for (instance, function_coverage) in function_coverage_map.iter_mut() { - if instance.def.attrs(tcx).len() > 0 { - continue; - } - // The covered function is not generic... - let covered_def_id = instance.def.def_id(); - if let Some(covered_file_name) = tcx.covered_file_name(covered_def_id) { - if !cgu_covered_files.remove(&covered_file_name) { - continue; - } - // The covered function's file is one of the files with unreachable code regions, so - // all of the unreachable code regions for this file will be added to this function. - for def_id in - unreachable_def_ids_by_file.remove(&covered_file_name).into_iter().flatten() - { - // Note, this loop adds an unreachable code regions for each MIR-derived region. - // Alternatively, we could add a single code region for the maximum span of all - // code regions here. - // - // Observed downsides of this approach are: - // - // 1. The coverage results will appear inconsistent compared with the same (or - // similar) code in a function that is reached. - // 2. If the function is unreachable from one crate but reachable when compiling - // another referencing crate (such as a cross-crate reference to a - // generic function or inlined function), actual coverage regions overlaid - // on a single larger code span of `Zero` coverage can appear confusing or - // wrong. Chaning the unreachable coverage from a `code_region` to a - // `gap_region` can help, but still can look odd with `0` line counts for - // lines between executed (> 0) lines (such as for blank lines or comments). - for ®ion in tcx.covered_code_regions(def_id) { - function_coverage.add_unreachable_region(region.clone()); - } - } - if cgu_covered_files.is_empty() { - break; - } + // For each file for which this CGU is responsible for adding unused function coverage, + // get the `def_id`s for each unused function (if any), define a synthetic function with a + // single LLVM coverage counter, and add the function's coverage `CodeRegion`s. to the + // function_coverage_map. + for covered_file_name in cgu_covered_files { + for def_id in unused_def_ids_by_file.remove(&covered_file_name).into_iter().flatten() { + cx.define_unused_fn(def_id); } } } diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs index e47b8fde40f..db61be407c9 100644 --- a/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs +++ b/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs @@ -1,5 +1,6 @@ use crate::llvm; +use crate::abi::{Abi, FnAbi}; use crate::builder::Builder; use crate::common::CodegenCx; @@ -7,33 +8,47 @@ use libc::c_uint; use llvm::coverageinfo::CounterMappingRegion; use rustc_codegen_ssa::coverageinfo::map::{CounterExpression, FunctionCoverage}; use rustc_codegen_ssa::traits::{ - BaseTypeMethods, CoverageInfoBuilderMethods, CoverageInfoMethods, MiscMethods, StaticMethods, + BaseTypeMethods, BuilderMethods, ConstMethods, CoverageInfoBuilderMethods, CoverageInfoMethods, + MiscMethods, StaticMethods, }; use rustc_data_structures::fx::FxHashMap; +use rustc_hir as hir; +use rustc_hir::def_id::DefId; use rustc_llvm::RustString; +use rustc_middle::bug; use rustc_middle::mir::coverage::{ CodeRegion, CounterValueReference, ExpressionOperandId, InjectedExpressionId, Op, }; +use rustc_middle::ty; +use rustc_middle::ty::layout::FnAbiExt; +use rustc_middle::ty::subst::InternalSubsts; use rustc_middle::ty::Instance; use std::cell::RefCell; use std::ffi::CString; +use std::iter; use tracing::debug; pub mod mapgen; +const UNUSED_FUNCTION_COUNTER_ID: CounterValueReference = CounterValueReference::START; + const VAR_ALIGN_BYTES: usize = 8; /// A context object for maintaining all state needed by the coverageinfo module. -pub struct CrateCoverageContext<'tcx> { +pub struct CrateCoverageContext<'ll, 'tcx> { // Coverage data for each instrumented function identified by DefId. pub(crate) function_coverage_map: RefCell<FxHashMap<Instance<'tcx>, FunctionCoverage<'tcx>>>, + pub(crate) pgo_func_name_var_map: RefCell<FxHashMap<Instance<'tcx>, &'ll llvm::Value>>, } -impl<'tcx> CrateCoverageContext<'tcx> { +impl<'ll, 'tcx> CrateCoverageContext<'ll, 'tcx> { pub fn new() -> Self { - Self { function_coverage_map: Default::default() } + Self { + function_coverage_map: Default::default(), + pgo_func_name_var_map: Default::default(), + } } pub fn take_function_coverage_map(&self) -> FxHashMap<Instance<'tcx>, FunctionCoverage<'tcx>> { @@ -41,23 +56,44 @@ impl<'tcx> CrateCoverageContext<'tcx> { } } -impl CoverageInfoMethods for CodegenCx<'ll, 'tcx> { +impl CoverageInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> { fn coverageinfo_finalize(&self) { mapgen::finalize(self) } -} -impl CoverageInfoBuilderMethods<'tcx> for Builder<'a, 'll, 'tcx> { - /// Calls llvm::createPGOFuncNameVar() with the given function instance's mangled function name. - /// The LLVM API returns an llvm::GlobalVariable containing the function name, with the specific - /// variable name and linkage required by LLVM InstrProf source-based coverage instrumentation. - fn create_pgo_func_name_var(&self, instance: Instance<'tcx>) -> Self::Value { - let llfn = self.cx.get_fn(instance); + fn get_pgo_func_name_var(&self, instance: Instance<'tcx>) -> &'ll llvm::Value { + if let Some(coverage_context) = self.coverage_context() { + debug!("getting pgo_func_name_var for instance={:?}", instance); + let mut pgo_func_name_var_map = coverage_context.pgo_func_name_var_map.borrow_mut(); + pgo_func_name_var_map + .entry(instance) + .or_insert_with(|| self.create_pgo_func_name_var(instance)) + } else { + bug!("Could not get the `coverage_context`"); + } + } + + /// Calls llvm::createPGOFuncNameVar() with the given function instance's + /// mangled function name. The LLVM API returns an llvm::GlobalVariable + /// containing the function name, with the specific variable name and + /// linkage required by LLVM InstrProf source-based coverage + /// instrumentation. Use `bx.get_pgo_func_name_var()` to ensure the variable + /// is only created once per `Instance`. + fn create_pgo_func_name_var(&self, instance: Instance<'tcx>) -> &'ll llvm::Value { let mangled_fn_name = CString::new(self.tcx.symbol_name(instance).name) .expect("error converting function name to C string"); + let llfn = self.get_fn(instance); unsafe { llvm::LLVMRustCoverageCreatePGOFuncNameVar(llfn, mangled_fn_name.as_ptr()) } } + fn define_unused_fn(&self, def_id: DefId) { + let instance = declare_unused_fn(self, &def_id); + codegen_unused_fn_and_counter(self, instance); + add_function_coverage(self, instance, def_id); + } +} + +impl CoverageInfoBuilderMethods<'tcx> for Builder<'a, 'll, 'tcx> { fn set_function_source_hash( &mut self, instance: Instance<'tcx>, @@ -145,6 +181,86 @@ impl CoverageInfoBuilderMethods<'tcx> for Builder<'a, 'll, 'tcx> { } } +fn declare_unused_fn(cx: &CodegenCx<'ll, 'tcx>, def_id: &DefId) -> Instance<'tcx> { + let tcx = cx.tcx; + + let instance = Instance::new( + *def_id, + InternalSubsts::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) + } + }), + ); + + let llfn = cx.declare_fn( + &tcx.symbol_name(instance).name, + &FnAbi::of_fn_ptr( + cx, + ty::Binder::dummy(tcx.mk_fn_sig( + iter::once(tcx.mk_unit()), + tcx.mk_unit(), + false, + hir::Unsafety::Unsafe, + Abi::Rust, + )), + &[], + ), + ); + + unsafe { + llvm::LLVMRustSetLinkage(llfn, llvm::Linkage::ExternalLinkage); + llvm::LLVMRustSetVisibility(llfn, llvm::Visibility::Hidden); + } + + cx.instances.borrow_mut().insert(instance, llfn); + + instance +} + +fn codegen_unused_fn_and_counter(cx: &CodegenCx<'ll, 'tcx>, instance: Instance<'tcx>) { + let llfn = cx.get_fn(instance); + let mut bx = Builder::new_block(cx, llfn, "unused_function"); + let fn_name = bx.get_pgo_func_name_var(instance); + let hash = bx.const_u64(0); + let num_counters = bx.const_u32(1); + let index = bx.const_u32(u32::from(UNUSED_FUNCTION_COUNTER_ID)); + debug!( + "codegen intrinsic instrprof.increment(fn_name={:?}, hash={:?}, num_counters={:?}, + index={:?}) for unused function: {:?}", + fn_name, hash, num_counters, index, instance + ); + bx.instrprof_increment(fn_name, hash, num_counters, index); + bx.ret_void(); +} + +fn add_function_coverage(cx: &CodegenCx<'ll, 'tcx>, instance: Instance<'tcx>, def_id: DefId) { + 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()); + } + // Add a Zero Counter for every code region. + // + // Even though the first coverage region already has an actual Counter, `llvm-cov` will not + // always report it. Re-adding an unreachable region (zero counter) for the same region + // seems to help produce the expected coverage. + function_coverage.add_unreachable_region(code_region.clone()); + } + + if let Some(coverage_context) = cx.coverage_context() { + coverage_context.function_coverage_map.borrow_mut().insert(instance, function_coverage); + } else { + bug!("Could not get the `coverage_context`"); + } +} + pub(crate) fn write_filenames_section_to_buffer<'a>( filenames: impl IntoIterator<Item = &'a CString>, buffer: &RustString, @@ -177,6 +293,7 @@ pub(crate) fn write_mapping_to_buffer( ); } } + pub(crate) fn hash_str(strval: &str) -> u64 { let strval = CString::new(strval).expect("null error converting hashable str to C string"); unsafe { llvm::LLVMRustCoverageHashCString(strval.as_ptr()) } |