src/librustc_codegen_llvm/coverageinfo/mapgen.rs

   1 use crate::common::CodegenCx;
   2 use crate::coverageinfo;
   3 use crate::llvm;
   4
   5 use llvm::coverageinfo::CounterMappingRegion;
   6 use log::debug;
   7 use rustc_codegen_ssa::coverageinfo::map::{Counter, CounterExpression, Region};
   8 use rustc_codegen_ssa::traits::{BaseTypeMethods, ConstMethods};
   9 use rustc_data_structures::fx::FxIndexSet;
  10 use rustc_llvm::RustString;
  11
  12 use std::ffi::CString;
  13
  14 /// Generates and exports the Coverage Map.
  15 ///
  16 /// This Coverage Map complies with Coverage Mapping Format version 3 (zero-based encoded as 2),
  17 /// as defined at [LLVM Code Coverage Mapping Format](https://github.com/rust-lang/llvm-project/blob/llvmorg-8.0.0/llvm/docs/CoverageMappingFormat.rst#llvm-code-coverage-mapping-format)
  18 /// and published in Rust's current (July 2020) fork of LLVM. This version is supported by the
  19 /// LLVM coverage tools (`llvm-profdata` and `llvm-cov`) bundled with Rust's fork of LLVM.
  20 ///
  21 /// Consequently, Rust's bundled version of Clang also generates Coverage Maps compliant with
  22 /// version 3. Clang's implementation of Coverage Map generation was referenced when implementing
  23 /// this Rust version, and though the format documentation is very explicit and detailed, some
  24 /// undocumented details in Clang's implementation (that may or may not be important) were also
  25 /// replicated for Rust's Coverage Map.
  26 pub fn finalize<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>) {
  27     let function_coverage_map = cx.coverage_context().take_function_coverage_map();
  28     if function_coverage_map.is_empty() {
  29         // This module has no functions with coverage instrumentation
  30         return;
  31     }
  32
  33     let mut mapgen = CoverageMapGenerator::new();
  34
  35     // Encode coverage mappings and generate function records
  36     let mut function_records = Vec::<&'ll llvm::Value>::new();
  37     let coverage_mappings_buffer = llvm::build_byte_buffer(|coverage_mappings_buffer| {
  38         for (instance, function_coverage) in function_coverage_map.into_iter() {
  39             debug!("Generate coverage map for: {:?}", instance);
  40
  41             let mangled_function_name = cx.tcx.symbol_name(instance).to_string();
  42             let function_source_hash = function_coverage.source_hash();
  43             let (expressions, counter_regions) =
  44                 function_coverage.get_expressions_and_counter_regions();
  45
  46             let old_len = coverage_mappings_buffer.len();
  47             mapgen.write_coverage_mappings(expressions, counter_regions, coverage_mappings_buffer);
  48             let mapping_data_size = coverage_mappings_buffer.len() - old_len;
  49             debug_assert!(
  50                 mapping_data_size > 0,
  51                 "Every `FunctionCoverage` should have at least one counter"
  52             );
  53
  54             let function_record = mapgen.make_function_record(
  55                 cx,
  56                 mangled_function_name,
  57                 function_source_hash,
  58                 mapping_data_size,
  59             );
  60             function_records.push(function_record);
  61         }
  62     });
  63
  64     // Encode all filenames referenced by counters/expressions in this module
  65     let filenames_buffer = llvm::build_byte_buffer(|filenames_buffer| {
  66         coverageinfo::write_filenames_section_to_buffer(&mapgen.filenames, filenames_buffer);
  67     });
  68
  69     // Generate the LLVM IR representation of the coverage map and store it in a well-known global
  70     mapgen.save_generated_coverage_map(
  71         cx,
  72         function_records,
  73         filenames_buffer,
  74         coverage_mappings_buffer,
  75     );
  76 }
  77
  78 struct CoverageMapGenerator {
  79     filenames: FxIndexSet<CString>,
  80 }
  81
  82 impl CoverageMapGenerator {
  83     fn new() -> Self {
  84         Self { filenames: FxIndexSet::default() }
  85     }
  86
  87     /// Using the `expressions` and `counter_regions` collected for the current function, generate
  88     /// the `mapping_regions` and `virtual_file_mapping`, and capture any new filenames. Then use
  89     /// LLVM APIs to encode the `virtual_file_mapping`, `expressions`, and `mapping_regions` into
  90     /// the given `coverage_mappings` byte buffer, compliant with the LLVM Coverage Mapping format.
  91     fn write_coverage_mappings(
  92         &mut self,
  93         expressions: Vec<CounterExpression>,
  94         counter_regions: impl Iterator<Item = (Counter, &'tcx Region<'tcx>)>,
  95         coverage_mappings_buffer: &RustString,
  96     ) {
  97         let mut counter_regions = counter_regions.collect::<Vec<_>>();
  98         if counter_regions.is_empty() {
  99             return;
 100         }
 101
 102         let mut virtual_file_mapping = Vec::new();
 103         let mut mapping_regions = Vec::new();
 104         let mut current_file_name = None;
 105         let mut current_file_id = 0;
 106
 107         // Convert the list of (Counter, Region) pairs to an array of `CounterMappingRegion`, sorted
 108         // by filename and position. Capture any new files to compute the `CounterMappingRegion`s
 109         // `file_id` (indexing files referenced by the current function), and construct the
 110         // function-specific `virtual_file_mapping` from `file_id` to its index in the module's
 111         // `filenames` array.
 112         counter_regions.sort_unstable_by_key(|(_counter, region)| *region);
 113         for (counter, region) in counter_regions {
 114             let Region { file_name, start_line, start_col, end_line, end_col } = *region;
 115             let same_file = current_file_name.as_ref().map_or(false, |p| p == file_name);
 116             if !same_file {
 117                 if current_file_name.is_some() {
 118                     current_file_id += 1;
 119                 }
 120                 current_file_name = Some(file_name.to_string());
 121                 let c_filename =
 122                     CString::new(file_name).expect("null error converting filename to C string");
 123                 debug!("  file_id: {} = '{:?}'", current_file_id, c_filename);
 124                 let (filenames_index, _) = self.filenames.insert_full(c_filename);
 125                 virtual_file_mapping.push(filenames_index as u32);
 126             }
 127             mapping_regions.push(CounterMappingRegion::code_region(
 128                 counter,
 129                 current_file_id,
 130                 start_line,
 131                 start_col,
 132                 end_line,
 133                 end_col,
 134             ));
 135         }
 136
 137         // Encode and append the current function's coverage mapping data
 138         coverageinfo::write_mapping_to_buffer(
 139             virtual_file_mapping,
 140             expressions,
 141             mapping_regions,
 142             coverage_mappings_buffer,
 143         );
 144     }
 145
 146     /// Generate and return the function record `Value`
 147     fn make_function_record(
 148         &mut self,
 149         cx: &CodegenCx<'ll, 'tcx>,
 150         mangled_function_name: String,
 151         function_source_hash: u64,
 152         mapping_data_size: usize,
 153     ) -> &'ll llvm::Value {
 154         let name_ref = coverageinfo::compute_hash(&mangled_function_name);
 155         let name_ref_val = cx.const_u64(name_ref);
 156         let mapping_data_size_val = cx.const_u32(mapping_data_size as u32);
 157         let func_hash_val = cx.const_u64(function_source_hash);
 158         cx.const_struct(
 159             &[name_ref_val, mapping_data_size_val, func_hash_val],
 160             /*packed=*/ true,
 161         )
 162     }
 163
 164     /// Combine the filenames and coverage mappings buffers, construct coverage map header and the
 165     /// array of function records, and combine everything into the complete coverage map. Save the
 166     /// coverage map data into the LLVM IR as a static global using a specific, well-known section
 167     /// and name.
 168     fn save_generated_coverage_map(
 169         self,
 170         cx: &CodegenCx<'ll, 'tcx>,
 171         function_records: Vec<&'ll llvm::Value>,
 172         filenames_buffer: Vec<u8>,
 173         mut coverage_mappings_buffer: Vec<u8>,
 174     ) {
 175         // Concatenate the encoded filenames and encoded coverage mappings, and add additional zero
 176         // bytes as-needed to ensure 8-byte alignment.
 177         let mut coverage_size = coverage_mappings_buffer.len();
 178         let filenames_size = filenames_buffer.len();
 179         let remaining_bytes =
 180             (filenames_size + coverage_size) % coverageinfo::COVMAP_VAR_ALIGN_BYTES;
 181         if remaining_bytes > 0 {
 182             let pad = coverageinfo::COVMAP_VAR_ALIGN_BYTES - remaining_bytes;
 183             coverage_mappings_buffer.append(&mut [0].repeat(pad));
 184             coverage_size += pad;
 185         }
 186         let filenames_and_coverage_mappings = [filenames_buffer, coverage_mappings_buffer].concat();
 187         let filenames_and_coverage_mappings_val =
 188             cx.const_bytes(&filenames_and_coverage_mappings[..]);
 189
 190         debug!(
 191             "cov map: n_records = {}, filenames_size = {}, coverage_size = {}, 0-based version = {}",
 192             function_records.len(),
 193             filenames_size,
 194             coverage_size,
 195             coverageinfo::mapping_version()
 196         );
 197
 198         // Create the coverage data header
 199         let n_records_val = cx.const_u32(function_records.len() as u32);
 200         let filenames_size_val = cx.const_u32(filenames_size as u32);
 201         let coverage_size_val = cx.const_u32(coverage_size as u32);
 202         let version_val = cx.const_u32(coverageinfo::mapping_version());
 203         let cov_data_header_val = cx.const_struct(
 204             &[n_records_val, filenames_size_val, coverage_size_val, version_val],
 205             /*packed=*/ false,
 206         );
 207
 208         // Create the function records array
 209         let name_ref_from_u64 = cx.type_i64();
 210         let mapping_data_size_from_u32 = cx.type_i32();
 211         let func_hash_from_u64 = cx.type_i64();
 212         let function_record_ty = cx.type_struct(
 213             &[name_ref_from_u64, mapping_data_size_from_u32, func_hash_from_u64],
 214             /*packed=*/ true,
 215         );
 216         let function_records_val = cx.const_array(function_record_ty, &function_records[..]);
 217
 218         // Create the complete LLVM coverage data value to add to the LLVM IR
 219         let cov_data_val = cx.const_struct(
 220             &[cov_data_header_val, function_records_val, filenames_and_coverage_mappings_val],
 221             /*packed=*/ false,
 222         );
 223
 224         // Save the coverage data value to LLVM IR
 225         coverageinfo::save_map_to_mod(cx, cov_data_val);
 226     }
 227 }