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//===- DWARFLinker.h --------------------------------------------*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#include "llvm/ADT/DenseMap.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/DWARFLinkerParallel/DWARFFile.h"
#include "llvm/DebugInfo/DWARF/DWARFContext.h"
#include "llvm/DebugInfo/DWARF/DWARFDie.h"
#include "llvm/MC/MCDwarf.h"
#include "llvm/TargetParser/Triple.h"
/// ------------------------------------------------------------------
/// The core of the Dwarf linking logic.
/// The generation of the dwarf information from the object files will be
/// driven by the selection of 'root DIEs', which are DIEs that
/// describe variables or functions that resolves to the corresponding
/// code section(and thus have entries in the Addresses map). All the debug
/// information that will be generated(the DIEs, but also the line
/// tables, ranges, ...) is derived from that set of root DIEs.
/// The root DIEs are identified because they contain relocations that
/// points to code section(the low_pc for a function, the location for
/// a variable). These relocations are gathered as a very first step
/// when we start processing a object file by AddressesMap.
/// The overall linking process looks like this:
/// parrallel_for_each(ObjectFile) {
/// for_each (Compile Unit) {
/// 1. Load Clang modules.
/// }
/// parrallel_for_each(Compile Unit) {
/// 1. Load input DWARF for Compile Unit.
/// 2. Report warnings for Clang modules.
/// 3. Analyze live DIEs and type names(if ODR deduplication is requested).
/// 4. Clone DIEs(Generate output DIEs and resulting DWARF tables).
/// The result is in an OutDebugInfoBytes, which is an ELF file
/// containing DWARF tables corresponding to the current compile unit.
/// 5. Cleanup Input and Output DIEs.
/// }
/// Deallocate loaded Object file.
/// }
/// if (ODR deduplication is requested)
/// Generate an artificial compilation unit ("Type Table": used to partially
/// generate DIEs at the clone stage).
/// for_each (ObjectFile) {
/// for_each (Compile Unit) {
/// 1. Set offsets to Compile Units DWARF tables.
/// 2. Sort offsets/attributes/patches to have a predictable result.
/// 3. Patch size/offsets fields.
/// 4. Generate index tables.
/// 5. Move DWARF tables of compile units into the resulting file.
/// }
/// }
/// Every compile unit is processed separately, visited only once
/// (except case inter-CU references exist), and used data is freed
/// after the compile unit is processed. The resulting file is glued together
/// from the generated debug tables which correspond to separate compile units.
/// Handling inter-CU references: inter-CU references are hard to process
/// using only one pass. f.e. if CU1 references CU100 and CU100 references
/// CU1, we could not finish handling of CU1 until we finished CU100.
/// Thus we either need to load all CUs into the memory, either load CUs several
/// times. This implementation loads inter-connected CU into memory at the first
/// pass and processes them at the second pass.
/// ODR deduplication: Artificial compilation unit will be constructed to keep
/// type dies. All types are moved into that compilation unit. Type's references
/// are patched so that they point to the corresponding types from artificial
/// compilation unit. All partial type definitions would be merged into single
/// type definition.
namespace llvm {
namespace dwarflinker_parallel {
/// ExtraDwarfEmitter allows adding extra data to the DWARFLinker output.
/// The finish() method should be called after all extra data are emitted.
class ExtraDwarfEmitter {
virtual ~ExtraDwarfEmitter() = default;
/// Dump the file to the disk.
virtual void finish() = 0;
/// Emit section named SecName with data SecData.
virtual void emitSectionContents(StringRef SecData, StringRef SecName) = 0;
/// Emit temporarily symbol named \p SymName inside section \p SecName.
virtual MCSymbol *emitTempSym(StringRef SecName, StringRef SymName) = 0;
/// Emit the swift_ast section stored in \p Buffer.
virtual void emitSwiftAST(StringRef Buffer) = 0;
/// Emit the swift reflection section stored in \p Buffer.
virtual void emitSwiftReflectionSection(
llvm::binaryformat::Swift5ReflectionSectionKind ReflSectionKind,
StringRef Buffer, uint32_t Alignment, uint32_t Size) = 0;
/// Returns underlying AsmPrinter.
virtual AsmPrinter &getAsmPrinter() const = 0;
class DWARFLinker {
/// Type of output file.
enum class OutputFileType {
/// The kind of accelerator tables we should emit.
enum class AccelTableKind : uint8_t {
Apple, ///< .apple_names, .apple_namespaces, .apple_types, .apple_objc.
Pub, ///< .debug_pubnames, .debug_pubtypes
DebugNames ///< .debug_names.
using MessageHandlerTy = std::function<void(
const Twine &Warning, StringRef Context, const DWARFDie *DIE)>;
using ObjFileLoaderTy = std::function<ErrorOr<DWARFFile &>(
StringRef ContainerName, StringRef Path)>;
using InputVerificationHandlerTy = std::function<void(const DWARFFile &File)>;
using ObjectPrefixMapTy = std::map<std::string, std::string>;
using CompileUnitHandlerTy = function_ref<void(const DWARFUnit &Unit)>;
using TranslatorFuncTy = std::function<StringRef(StringRef)>;
using SwiftInterfacesMapTy = std::map<std::string, std::string>;
virtual ~DWARFLinker() = default;
/// Creates dwarf linker instance.
static std::unique_ptr<DWARFLinker>
createLinker(MessageHandlerTy ErrorHandler, MessageHandlerTy WarningHandler,
TranslatorFuncTy StringsTranslator = nullptr);
/// Creates emitter for output dwarf.
virtual Error createEmitter(const Triple &TheTriple, OutputFileType FileType,
raw_pwrite_stream &OutFile) = 0;
/// Returns previously created dwarf emitter. May be nullptr.
virtual ExtraDwarfEmitter *getEmitter() = 0;
/// Add object file to be linked. Pre-load compile unit die. Call
/// \p OnCUDieLoaded for each compile unit die. If specified \p File
/// has reference to the Clang module then such module would be
/// pre-loaded by \p Loader for !Update case.
/// \pre NoODR, Update options should be set before call to addObjectFile.
virtual void addObjectFile(
DWARFFile &File, ObjFileLoaderTy Loader = nullptr,
CompileUnitHandlerTy OnCUDieLoaded = [](const DWARFUnit &) {}) = 0;
/// Link debug info for added files.
virtual Error link() = 0;
/// \defgroup Methods setting various linking options:
/// @{
/// Allows to generate log of linking process to the standard output.
virtual void setVerbosity(bool Verbose) = 0;
/// Print statistics to standard output.
virtual void setStatistics(bool Statistics) = 0;
/// Verify the input DWARF.
virtual void setVerifyInputDWARF(bool Verify) = 0;
/// Do not unique types according to ODR.
virtual void setNoODR(bool NoODR) = 0;
/// Update index tables only(do not modify rest of DWARF).
virtual void setUpdateIndexTablesOnly(bool UpdateIndexTablesOnly) = 0;
/// Allow generating valid, but non-deterministic output.
virtual void
setAllowNonDeterministicOutput(bool AllowNonDeterministicOutput) = 0;
/// Set to keep the enclosing function for a static variable.
virtual void setKeepFunctionForStatic(bool KeepFunctionForStatic) = 0;
/// Use specified number of threads for parallel files linking.
virtual void setNumThreads(unsigned NumThreads) = 0;
/// Add kind of accelerator tables to be generated.
virtual void addAccelTableKind(AccelTableKind Kind) = 0;
/// Set prepend path for clang modules.
virtual void setPrependPath(const std::string &Ppath) = 0;
/// Set estimated objects files amount, for preliminary data allocation.
virtual void setEstimatedObjfilesAmount(unsigned ObjFilesNum) = 0;
/// Set verification handler which would be used to report verification
/// errors.
virtual void
setInputVerificationHandler(InputVerificationHandlerTy Handler) = 0;
/// Set map for Swift interfaces.
virtual void setSwiftInterfacesMap(SwiftInterfacesMapTy *Map) = 0;
/// Set prefix map for objects.
virtual void setObjectPrefixMap(ObjectPrefixMapTy *Map) = 0;
/// Set target DWARF version.
virtual Error setTargetDWARFVersion(uint16_t TargetDWARFVersion) = 0;
/// @}
} // end namespace dwarflinker_parallel
} // end namespace llvm