| //===- DWARFLinker.h --------------------------------------------*- C++ -*-===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_DWARFLINKER_PARALLEL_DWARFLINKER_H |
| #define LLVM_DWARFLINKER_PARALLEL_DWARFLINKER_H |
| |
| #include "llvm/CodeGen/AsmPrinter.h" |
| #include "llvm/DWARFLinker/DWARFFile.h" |
| #include "llvm/DWARFLinker/DWARFLinkerBase.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 dwarf_linker { |
| namespace parallel { |
| |
| /// This structure keeps data of the concrete section. |
| struct SectionDescriptorBase { |
| SectionDescriptorBase(DebugSectionKind SectionKind, dwarf::FormParams Format, |
| llvm::endianness Endianess) |
| : SectionKind(SectionKind), Format(Format), Endianess(Endianess) {} |
| virtual ~SectionDescriptorBase() = default; |
| /// Returns section content. |
| virtual StringRef getContents() = 0; |
| /// Returns section kind. |
| DebugSectionKind getKind() { return SectionKind; } |
| /// Returns section name. |
| const StringLiteral &getName() const { return getSectionName(SectionKind); } |
| /// Returns endianess used by section. |
| llvm::endianness getEndianess() const { return Endianess; } |
| /// Returns FormParams used by section. |
| dwarf::FormParams getFormParams() const { return Format; } |
| |
| protected: |
| /// The section kind. |
| DebugSectionKind SectionKind = DebugSectionKind::NumberOfEnumEntries; |
| /// Output format. |
| dwarf::FormParams Format = {4, 4, dwarf::DWARF32}; |
| llvm::endianness Endianess = llvm::endianness::little; |
| }; |
| |
| using SectionHandlerTy = |
| std::function<void(std::shared_ptr<SectionDescriptorBase> Section)>; |
| |
| class DWARFLinker : public DWARFLinkerBase { |
| public: |
| virtual ~DWARFLinker() = default; |
| |
| /// Creates dwarf linker instance. |
| static std::unique_ptr<DWARFLinker> |
| createLinker(MessageHandlerTy ErrorHandler, MessageHandlerTy WarningHandler, |
| TranslatorFuncTy StringsTranslator = nullptr); |
| |
| /// Set output DWARF handler. Result of linking DWARF is set of sections |
| /// containing final debug info. DWARFLinkerBase::link() pass generated |
| /// sections using specified \p SectionHandler. |
| virtual void setOutputDWARFHandler(const Triple &TargetTriple, |
| SectionHandlerTy SectionHandler) = 0; |
| }; |
| |
| } // end of namespace parallel |
| } // end of namespace dwarf_linker |
| } // end of namespace llvm |
| |
| #endif // LLVM_DWARFLINKER_PARALLEL_DWARFLINKER_H |