1 //===- llvm/CodeGen/DwarfStringPool.cpp - Dwarf Debug Framework -----------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 10 #include "DwarfStringPool.h" 11 #include "llvm/ADT/SmallVector.h" 12 #include "llvm/ADT/StringRef.h" 13 #include "llvm/ADT/Twine.h" 14 #include "llvm/CodeGen/AsmPrinter.h" 15 #include "llvm/MC/MCAsmInfo.h" 16 #include "llvm/MC/MCStreamer.h" 17 #include <cassert> 18 #include <utility> 19 20 using namespace llvm; 21 22 DwarfStringPool::DwarfStringPool(BumpPtrAllocator &A, AsmPrinter &Asm, 23 StringRef Prefix) 24 : Pool(A), Prefix(Prefix), 25 ShouldCreateSymbols(Asm.MAI->doesDwarfUseRelocationsAcrossSections()) {} 26 27 StringMapEntry<DwarfStringPool::EntryTy> & 28 DwarfStringPool::getEntryImpl(AsmPrinter &Asm, StringRef Str) { 29 auto I = Pool.insert(std::make_pair(Str, EntryTy())); 30 auto &Entry = I.first->second; 31 if (I.second) { 32 Entry.Index = EntryTy::NotIndexed; 33 Entry.Offset = NumBytes; 34 Entry.Symbol = ShouldCreateSymbols ? Asm.createTempSymbol(Prefix) : nullptr; 35 36 NumBytes += Str.size() + 1; 37 assert(NumBytes > Entry.Offset && "Unexpected overflow"); 38 } 39 return *I.first; 40 } 41 42 DwarfStringPool::EntryRef DwarfStringPool::getEntry(AsmPrinter &Asm, 43 StringRef Str) { 44 auto &MapEntry = getEntryImpl(Asm, Str); 45 return EntryRef(MapEntry, false); 46 } 47 48 DwarfStringPool::EntryRef DwarfStringPool::getIndexedEntry(AsmPrinter &Asm, 49 StringRef Str) { 50 auto &MapEntry = getEntryImpl(Asm, Str); 51 if (!MapEntry.getValue().isIndexed()) 52 MapEntry.getValue().Index = NumIndexedStrings++; 53 return EntryRef(MapEntry, true); 54 } 55 56 void DwarfStringPool::emitStringOffsetsTableHeader(AsmPrinter &Asm, 57 MCSection *Section, 58 MCSymbol *StartSym) { 59 if (getNumIndexedStrings() == 0) 60 return; 61 Asm.OutStreamer->SwitchSection(Section); 62 unsigned EntrySize = 4; 63 // FIXME: DWARF64 64 // We are emitting the header for a contribution to the string offsets 65 // table. The header consists of an entry with the contribution's 66 // size (not including the size of the length field), the DWARF version and 67 // 2 bytes of padding. 68 Asm.emitInt32(getNumIndexedStrings() * EntrySize + 4); 69 Asm.emitInt16(Asm.getDwarfVersion()); 70 Asm.emitInt16(0); 71 // Define the symbol that marks the start of the contribution. It is 72 // referenced by most unit headers via DW_AT_str_offsets_base. 73 // Split units do not use the attribute. 74 if (StartSym) 75 Asm.OutStreamer->EmitLabel(StartSym); 76 } 77 78 void DwarfStringPool::emit(AsmPrinter &Asm, MCSection *StrSection, 79 MCSection *OffsetSection, bool UseRelativeOffsets) { 80 if (Pool.empty()) 81 return; 82 83 // Start the dwarf str section. 84 Asm.OutStreamer->SwitchSection(StrSection); 85 86 // Get all of the string pool entries and sort them by their offset. 87 SmallVector<const StringMapEntry<EntryTy> *, 64> Entries; 88 Entries.reserve(Pool.size()); 89 90 for (const auto &E : Pool) 91 Entries.push_back(&E); 92 93 llvm::sort( 94 Entries.begin(), Entries.end(), 95 [](const StringMapEntry<EntryTy> *A, const StringMapEntry<EntryTy> *B) { 96 return A->getValue().Offset < B->getValue().Offset; 97 }); 98 99 for (const auto &Entry : Entries) { 100 assert(ShouldCreateSymbols == static_cast<bool>(Entry->getValue().Symbol) && 101 "Mismatch between setting and entry"); 102 103 // Emit a label for reference from debug information entries. 104 if (ShouldCreateSymbols) 105 Asm.OutStreamer->EmitLabel(Entry->getValue().Symbol); 106 107 // Emit the string itself with a terminating null byte. 108 Asm.OutStreamer->AddComment("string offset=" + 109 Twine(Entry->getValue().Offset)); 110 Asm.OutStreamer->EmitBytes( 111 StringRef(Entry->getKeyData(), Entry->getKeyLength() + 1)); 112 } 113 114 // If we've got an offset section go ahead and emit that now as well. 115 if (OffsetSection) { 116 // Now only take the indexed entries and put them in an array by their ID so 117 // we can emit them in order. 118 Entries.resize(NumIndexedStrings); 119 for (const auto &Entry : Pool) { 120 if (Entry.getValue().isIndexed()) 121 Entries[Entry.getValue().Index] = &Entry; 122 } 123 124 Asm.OutStreamer->SwitchSection(OffsetSection); 125 unsigned size = 4; // FIXME: DWARF64 is 8. 126 for (const auto &Entry : Entries) 127 if (UseRelativeOffsets) 128 Asm.emitDwarfStringOffset(Entry->getValue()); 129 else 130 Asm.OutStreamer->EmitIntValue(Entry->getValue().Offset, size); 131 } 132 } 133