Index: include/llvm/ADT/MapVector.h =================================================================== --- include/llvm/ADT/MapVector.h +++ include/llvm/ADT/MapVector.h @@ -123,6 +123,15 @@ Map.erase(Pos); Vector.pop_back(); } + + /// \brief Remove the element given by Iterator. + /// Returns an iterator to the element following the one which was removed, + /// which may be end(). + typename VectorType::iterator erase(typename VectorType::iterator Iterator) { + typename MapType::iterator MapIterator = Map.find(Iterator->first); + Map.erase(MapIterator); + return Vector.erase(Iterator); + } }; } Index: include/llvm/MC/MCContext.h =================================================================== --- include/llvm/MC/MCContext.h +++ include/llvm/MC/MCContext.h @@ -11,10 +11,12 @@ #define LLVM_MC_MCCONTEXT_H #include "llvm/ADT/DenseMap.h" +#include "llvm/ADT/SetVector.h" #include "llvm/ADT/SmallString.h" #include "llvm/ADT/SmallVector.h" #include "llvm/ADT/StringMap.h" #include "llvm/MC/MCDwarf.h" +#include "llvm/MC/MCStreamer.h" #include "llvm/MC/SectionKind.h" #include "llvm/Support/Allocator.h" #include "llvm/Support/Compiler.h" @@ -129,11 +131,10 @@ /// assembly source files. unsigned GenDwarfFileNumber; - /// The default initial text section that we generate dwarf debugging line - /// info for when generating dwarf assembly source files. - const MCSection *GenDwarfSection; - /// Symbols created for the start and end of this section. - MCSymbol *GenDwarfSectionStartSym, *GenDwarfSectionEndSym; + /// Symbols created for the start and end of each section, used for + /// generating the .debug_ranges and .debug_aranges sections. + MapVector > + SectionStartEndSyms; /// The information gathered from labels that will have dwarf label /// entries when generating dwarf assembly source files. @@ -376,16 +377,18 @@ void setGenDwarfFileNumber(unsigned FileNumber) { GenDwarfFileNumber = FileNumber; } - const MCSection *getGenDwarfSection() { return GenDwarfSection; } - void setGenDwarfSection(const MCSection *Sec) { GenDwarfSection = Sec; } - MCSymbol *getGenDwarfSectionStartSym() { return GenDwarfSectionStartSym; } - void setGenDwarfSectionStartSym(MCSymbol *Sym) { - GenDwarfSectionStartSym = Sym; + MapVector > & + getGenDwarfSectionSyms() { + return SectionStartEndSyms; } - MCSymbol *getGenDwarfSectionEndSym() { return GenDwarfSectionEndSym; } - void setGenDwarfSectionEndSym(MCSymbol *Sym) { - GenDwarfSectionEndSym = Sym; + std::pair >::iterator, + bool> + addGenDwarfSection(const MCSection *Sec) { + return SectionStartEndSyms.insert( + std::make_pair(Sec, std::make_pair(nullptr, nullptr))); } + void finalizeDwarfSections(MCStreamer &MCOS); const std::vector &getMCGenDwarfLabelEntries() const { return MCGenDwarfLabelEntries; } Index: include/llvm/MC/MCObjectStreamer.h =================================================================== --- include/llvm/MC/MCObjectStreamer.h +++ include/llvm/MC/MCObjectStreamer.h @@ -117,6 +117,10 @@ void EmitFill(uint64_t NumBytes, uint8_t FillValue) override; void EmitZeros(uint64_t NumBytes) override; void FinishImpl() override; + + virtual bool mayHaveInstructions() const { + return getCurrentSectionData()->hasInstructions(); + } }; } // end namespace llvm Index: include/llvm/MC/MCStreamer.h =================================================================== --- include/llvm/MC/MCStreamer.h +++ include/llvm/MC/MCStreamer.h @@ -732,6 +732,8 @@ virtual void FinishImpl() = 0; /// Finish - Finish emission of machine code. void Finish(); + + virtual bool mayHaveInstructions() const { return true; } }; /// createNullStreamer - Create a dummy machine code streamer, which does Index: lib/MC/MCContext.cpp =================================================================== --- lib/MC/MCContext.cpp +++ lib/MC/MCContext.cpp @@ -339,6 +339,29 @@ return !MCDwarfFiles[FileNumber].Name.empty(); } +/// finalizeDwarfSections - Emit end symbols for each non-empty code section. +/// Also remove empty sections from SectionStartEndSyms, to avoid generating +/// useless debug info for them. +void MCContext::finalizeDwarfSections(MCStreamer &MCOS) { + MCContext &context = MCOS.getContext(); + + auto sec = SectionStartEndSyms.begin(); + while (sec != SectionStartEndSyms.end()) { + assert(sec->second.first && "Start symbol must be set by now"); + MCOS.SwitchSection(sec->first); + if (MCOS.mayHaveInstructions()) { + MCSymbol *SectionEndSym = context.CreateTempSymbol(); + MCOS.EmitLabel(SectionEndSym); + sec->second.second = SectionEndSym; + ++sec; + } else { + MapVector >::iterator + to_erase = sec; + sec = SectionStartEndSyms.erase(to_erase); + } + } +} + void MCContext::FatalError(SMLoc Loc, const Twine &Msg) { // If we have a source manager and a location, use it. Otherwise just // use the generic report_fatal_error(). Index: lib/MC/MCDwarf.cpp =================================================================== --- lib/MC/MCDwarf.cpp +++ lib/MC/MCDwarf.cpp @@ -17,7 +17,9 @@ #include "llvm/MC/MCContext.h" #include "llvm/MC/MCExpr.h" #include "llvm/MC/MCObjectFileInfo.h" +#include "llvm/MC/MCObjectStreamer.h" #include "llvm/MC/MCRegisterInfo.h" +#include "llvm/MC/MCSection.h" #include "llvm/MC/MCStreamer.h" #include "llvm/MC/MCSymbol.h" #include "llvm/Support/Debug.h" @@ -518,8 +520,12 @@ MCOS->EmitULEB128IntValue(dwarf::DW_TAG_compile_unit); MCOS->EmitIntValue(dwarf::DW_CHILDREN_yes, 1); EmitAbbrev(MCOS, dwarf::DW_AT_stmt_list, dwarf::DW_FORM_data4); - EmitAbbrev(MCOS, dwarf::DW_AT_low_pc, dwarf::DW_FORM_addr); - EmitAbbrev(MCOS, dwarf::DW_AT_high_pc, dwarf::DW_FORM_addr); + if (MCOS->getContext().getGenDwarfSectionSyms().size() > 1) { + EmitAbbrev(MCOS, dwarf::DW_AT_ranges, dwarf::DW_FORM_data4); + } else { + EmitAbbrev(MCOS, dwarf::DW_AT_low_pc, dwarf::DW_FORM_addr); + EmitAbbrev(MCOS, dwarf::DW_AT_high_pc, dwarf::DW_FORM_addr); + } EmitAbbrev(MCOS, dwarf::DW_AT_name, dwarf::DW_FORM_string); if (!context.getCompilationDir().empty()) EmitAbbrev(MCOS, dwarf::DW_AT_comp_dir, dwarf::DW_FORM_string); @@ -552,20 +558,14 @@ } // When generating dwarf for assembly source files this emits the data for -// .debug_aranges section. Which contains a header and a table of pairs of -// PointerSize'ed values for the address and size of section(s) with line table -// entries (just the default .text in our case) and a terminating pair of zeros. +// .debug_aranges section. This section contains a header and a table of pairs +// of PointerSize'ed values for the address and size of section(s) with line +// table entries. static void EmitGenDwarfAranges(MCStreamer *MCOS, const MCSymbol *InfoSectionSymbol) { MCContext &context = MCOS->getContext(); - // Create a symbol at the end of the section that we are creating the dwarf - // debugging info to use later in here as part of the expression to calculate - // the size of the section for the table. - MCOS->SwitchSection(context.getGenDwarfSection()); - MCSymbol *SectionEndSym = context.CreateTempSymbol(); - MCOS->EmitLabel(SectionEndSym); - context.setGenDwarfSectionEndSym(SectionEndSym); + auto &Sections = context.getGenDwarfSectionSyms(); MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfARangesSection()); @@ -583,8 +583,8 @@ Length += Pad; // Add the size of the pair of PointerSize'ed values for the address and size - // of the one default .text section we have in the table. - Length += 2 * AddrSize; + // of each section we have in the table. + Length += 2 * AddrSize * Sections.size(); // And the pair of terminating zeros. Length += 2 * AddrSize; @@ -608,14 +608,21 @@ for(int i = 0; i < Pad; i++) MCOS->EmitIntValue(0, 1); - // Now emit the table of pairs of PointerSize'ed values for the section(s) - // address and size, in our case just the one default .text section. - const MCExpr *Addr = MCSymbolRefExpr::Create( - context.getGenDwarfSectionStartSym(), MCSymbolRefExpr::VK_None, context); - const MCExpr *Size = MakeStartMinusEndExpr(*MCOS, - *context.getGenDwarfSectionStartSym(), *SectionEndSym, 0); - MCOS->EmitValue(Addr, AddrSize); - MCOS->EmitAbsValue(Size, AddrSize); + // Now emit the table of pairs of PointerSize'ed values for the section + // addresses and sizes. + for (const auto &sec : Sections) { + MCSymbol* StartSymbol = sec.second.first; + MCSymbol* EndSymbol = sec.second.second; + assert(StartSymbol && "StartSymbol must not be NULL"); + assert(EndSymbol && "EndSymbol must not be NULL"); + + const MCExpr *Addr = MCSymbolRefExpr::Create( + StartSymbol, MCSymbolRefExpr::VK_None, context); + const MCExpr *Size = MakeStartMinusEndExpr(*MCOS, + *StartSymbol, *EndSymbol, 0); + MCOS->EmitValue(Addr, AddrSize); + MCOS->EmitAbsValue(Size, AddrSize); + } // And finally the pair of terminating zeros. MCOS->EmitIntValue(0, AddrSize); @@ -627,7 +634,8 @@ // DIE and a list of label DIEs. static void EmitGenDwarfInfo(MCStreamer *MCOS, const MCSymbol *AbbrevSectionSymbol, - const MCSymbol *LineSectionSymbol) { + const MCSymbol *LineSectionSymbol, + const MCSymbol *RangesSectionSymbol) { MCContext &context = MCOS->getContext(); MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfInfoSection()); @@ -674,15 +682,37 @@ MCOS->EmitIntValue(0, 4); } - // AT_low_pc, the first address of the default .text section. - const MCExpr *Start = MCSymbolRefExpr::Create( - context.getGenDwarfSectionStartSym(), MCSymbolRefExpr::VK_None, context); - MCOS->EmitValue(Start, AddrSize); + if (RangesSectionSymbol) { + // There are multiple sections containing code, so we must use the + // .debug_ranges sections. - // AT_high_pc, the last address of the default .text section. - const MCExpr *End = MCSymbolRefExpr::Create( - context.getGenDwarfSectionEndSym(), MCSymbolRefExpr::VK_None, context); - MCOS->EmitValue(End, AddrSize); + // AT_ranges, the 4 byte offset from the start of the .debug_ranges section + // to the address range list for this compilation unit. + MCOS->EmitSymbolValue(RangesSectionSymbol, 4); + } else { + // If we only have one non-empty code section, we can use the simpler + // AT_low_pc and AT_high_pc attributes. + + // Find the first (and only) non-empty text section + auto &Sections = context.getGenDwarfSectionSyms(); + const auto TextSection = Sections.begin(); + assert(TextSection != Sections.end() && "No text section found"); + + MCSymbol* StartSymbol = TextSection->second.first; + MCSymbol* EndSymbol = TextSection->second.second; + assert(StartSymbol && "StartSymbol must not be NULL"); + assert(EndSymbol && "EndSymbol must not be NULL"); + + // AT_low_pc, the first address of the default .text section. + const MCExpr *Start = MCSymbolRefExpr::Create( + StartSymbol, MCSymbolRefExpr::VK_None, context); + MCOS->EmitValue(Start, AddrSize); + + // AT_high_pc, the last address of the default .text section. + const MCExpr *End = MCSymbolRefExpr::Create( + EndSymbol, MCSymbolRefExpr::VK_None, context); + MCOS->EmitValue(End, AddrSize); + } // AT_name, the name of the source file. Reconstruct from the first directory // and file table entries. @@ -766,13 +796,51 @@ MCOS->EmitLabel(InfoEnd); } +// When generating dwarf for assembly source files this emits the data for +// .debug_ranges section. We only emit one range list, which spans all of the +// executable sections of this file. +static void EmitGenDwarfRanges(MCStreamer *MCOS) { + MCContext &context = MCOS->getContext(); + auto &Sections = context.getGenDwarfSectionSyms(); + + const MCAsmInfo *AsmInfo = context.getAsmInfo(); + int AddrSize = AsmInfo->getPointerSize(); + + MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfRangesSection()); + + for (const auto sec : Sections) { + + MCSymbol* StartSymbol = sec.second.first; + MCSymbol* EndSymbol = sec.second.second; + assert(StartSymbol && "StartSymbol must not be NULL"); + assert(EndSymbol && "EndSymbol must not be NULL"); + + // Emit a base address selection entry for the start of this section + const MCExpr *SectionStartAddr = MCSymbolRefExpr::Create( + StartSymbol, MCSymbolRefExpr::VK_None, context); + MCOS->EmitFill(AddrSize, 0xFF); + MCOS->EmitValue(SectionStartAddr, AddrSize); + + // Emit a range list entry spanning this section + const MCExpr *SectionSize = MakeStartMinusEndExpr(*MCOS, + *StartSymbol, *EndSymbol, 0); + MCOS->EmitIntValue(0, AddrSize); + MCOS->EmitAbsValue(SectionSize, AddrSize); + } + + // Emit end of list entry + MCOS->EmitIntValue(0, AddrSize); + MCOS->EmitIntValue(0, AddrSize); +} + // // When generating dwarf for assembly source files this emits the Dwarf // sections. // void MCGenDwarfInfo::Emit(MCStreamer *MCOS) { - // Create the dwarf sections in this order (.debug_line already created). MCContext &context = MCOS->getContext(); + + // Create the dwarf sections in this order (.debug_line already created). const MCAsmInfo *AsmInfo = context.getAsmInfo(); bool CreateDwarfSectionSymbols = AsmInfo->doesDwarfUseRelocationsAcrossSections(); @@ -781,6 +849,22 @@ LineSectionSymbol = MCOS->getDwarfLineTableSymbol(0); MCSymbol *AbbrevSectionSymbol = nullptr; MCSymbol *InfoSectionSymbol = nullptr; + MCSymbol *RangesSectionSymbol = NULL; + + // Create end symbols for each section, and remove empty sections + MCOS->getContext().finalizeDwarfSections(*MCOS); + + // If there are no sections to generate debug info for, we don't need + // to do anything + if (MCOS->getContext().getGenDwarfSectionSyms().empty()) + return; + + // We only need to use the .debug_ranges section if we have multiple + // code sections. + const bool UseRangesSection = + MCOS->getContext().getGenDwarfSectionSyms().size() > 1; + CreateDwarfSectionSymbols |= UseRangesSection; + MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfInfoSection()); if (CreateDwarfSectionSymbols) { InfoSectionSymbol = context.CreateTempSymbol(); @@ -791,20 +875,30 @@ AbbrevSectionSymbol = context.CreateTempSymbol(); MCOS->EmitLabel(AbbrevSectionSymbol); } - MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfARangesSection()); + if (UseRangesSection) { + MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfRangesSection()); + if (CreateDwarfSectionSymbols) { + RangesSectionSymbol = context.CreateTempSymbol(); + MCOS->EmitLabel(RangesSectionSymbol); + } + } - // If there are no line table entries then do not emit any section contents. - if (!context.hasMCLineSections()) - return; + assert((RangesSectionSymbol != NULL) || !UseRangesSection); + + MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfARangesSection()); // Output the data for .debug_aranges section. EmitGenDwarfAranges(MCOS, InfoSectionSymbol); + if (UseRangesSection) + EmitGenDwarfRanges(MCOS); + // Output the data for .debug_abbrev section. EmitGenDwarfAbbrev(MCOS); // Output the data for .debug_info section. - EmitGenDwarfInfo(MCOS, AbbrevSectionSymbol, LineSectionSymbol); + EmitGenDwarfInfo(MCOS, AbbrevSectionSymbol, LineSectionSymbol, + RangesSectionSymbol); } // @@ -815,12 +909,13 @@ // void MCGenDwarfLabelEntry::Make(MCSymbol *Symbol, MCStreamer *MCOS, SourceMgr &SrcMgr, SMLoc &Loc) { - // We won't create dwarf labels for temporary symbols or symbols not in - // the default text. + // We won't create dwarf labels for temporary symbols. if (Symbol->isTemporary()) return; MCContext &context = MCOS->getContext(); - if (context.getGenDwarfSection() != MCOS->getCurrentSection().first) + // We won't create dwarf labels for symbols in sections that we are not + // generating debug info for. + if (!context.getGenDwarfSectionSyms().count(MCOS->getCurrentSection().first)) return; // The dwarf label's name does not have the symbol name's leading Index: lib/MC/MCParser/AsmParser.cpp =================================================================== --- lib/MC/MCParser/AsmParser.cpp +++ lib/MC/MCParser/AsmParser.cpp @@ -636,10 +636,12 @@ // If we are generating dwarf for assembly source files save the initial text // section and generate a .file directive. if (getContext().getGenDwarfForAssembly()) { - getContext().setGenDwarfSection(getStreamer().getCurrentSection().first); MCSymbol *SectionStartSym = getContext().CreateTempSymbol(); getStreamer().EmitLabel(SectionStartSym); - getContext().setGenDwarfSectionStartSym(SectionStartSym); + auto InsertResult = getContext().addGenDwarfSection( + getStreamer().getCurrentSection().first); + assert(InsertResult.second && ".text section should not have debug info yet"); + InsertResult.first->second.first = SectionStartSym; getContext().setGenDwarfFileNumber(getStreamer().EmitDwarfFileDirective( 0, StringRef(), getContext().getMainFileName())); } @@ -1578,12 +1580,11 @@ printMessage(IDLoc, SourceMgr::DK_Note, OS.str()); } - // If we are generating dwarf for assembly source files and the current - // section is the initial text section then generate a .loc directive for - // the instruction. + // If we are generating dwarf for the current section then generate a .loc + // directive for the instruction. if (!HadError && getContext().getGenDwarfForAssembly() && - getContext().getGenDwarfSection() == - getStreamer().getCurrentSection().first) { + getContext().getGenDwarfSectionSyms().count( + getStreamer().getCurrentSection().first)) { unsigned Line = SrcMgr.FindLineNumber(IDLoc, CurBuffer); @@ -2000,7 +2001,7 @@ break; if (FAI >= NParameters) { - assert(M && "expected macro to be defined"); + assert(M && "expected macro to be defined"); Error(IDLoc, "parameter named '" + FA.Name + "' does not exist for macro '" + M->Name + "'"); Index: lib/MC/MCParser/ELFAsmParser.cpp =================================================================== --- lib/MC/MCParser/ELFAsmParser.cpp +++ lib/MC/MCParser/ELFAsmParser.cpp @@ -150,7 +150,7 @@ private: bool ParseSectionName(StringRef &SectionName); - bool ParseSectionArguments(bool IsPush); + bool ParseSectionArguments(bool IsPush, SMLoc loc); unsigned parseSunStyleSectionFlags(); }; @@ -382,7 +382,7 @@ bool ELFAsmParser::ParseDirectivePushSection(StringRef s, SMLoc loc) { getStreamer().PushSection(); - if (ParseSectionArguments(/*IsPush=*/true)) { + if (ParseSectionArguments(/*IsPush=*/true, loc)) { getStreamer().PopSection(); return true; } @@ -397,11 +397,11 @@ } // FIXME: This is a work in progress. -bool ELFAsmParser::ParseDirectiveSection(StringRef, SMLoc) { - return ParseSectionArguments(/*IsPush=*/false); +bool ELFAsmParser::ParseDirectiveSection(StringRef, SMLoc loc) { + return ParseSectionArguments(/*IsPush=*/false, loc); } -bool ELFAsmParser::ParseSectionArguments(bool IsPush) { +bool ELFAsmParser::ParseSectionArguments(bool IsPush, SMLoc loc) { StringRef SectionName; if (ParseSectionName(SectionName)) @@ -545,10 +545,24 @@ } SectionKind Kind = computeSectionKind(Flags, Size); - getStreamer().SwitchSection(getContext().getELFSection(SectionName, Type, - Flags, Kind, Size, - GroupName), - Subsection); + const MCSection *ELFSection = getContext().getELFSection( + SectionName, Type, Flags, Kind, Size, GroupName); + getStreamer().SwitchSection(ELFSection, Subsection); + + if (getContext().getGenDwarfForAssembly()) { + auto &Sections = getContext().getGenDwarfSectionSyms(); + auto InsertResult = Sections.insert( + std::make_pair(ELFSection, std::make_pair(nullptr, nullptr))); + if (InsertResult.second) { + if (getContext().getDwarfVersion() <= 2) + Error(loc, "DWARF2 only supports one section per compilation unit"); + + MCSymbol *SectionStartSymbol = getContext().CreateTempSymbol(); + getStreamer().EmitLabel(SectionStartSymbol); + InsertResult.first->second.first = SectionStartSymbol; + } + } + return false; }