From 53187f1eeccb22ab6ef3f5ba5acfbe0ebeed1dbd Mon Sep 17 00:00:00 2001 From: Fangrui Song Date: Sat, 13 Feb 2021 14:52:30 -0800 Subject: [PATCH] ELFObjectWriter: Simplify * Delete unused ELFSymbolData::operator< * Inline createStringTable * Fix a comment * Change align to return uint64_t --- llvm/lib/MC/ELFObjectWriter.cpp | 57 ++++++++++------------------------------- 1 file changed, 13 insertions(+), 44 deletions(-) diff --git a/llvm/lib/MC/ELFObjectWriter.cpp b/llvm/lib/MC/ELFObjectWriter.cpp index 714fc98..14556d3 100644 --- a/llvm/lib/MC/ELFObjectWriter.cpp +++ b/llvm/lib/MC/ELFObjectWriter.cpp @@ -119,19 +119,6 @@ struct ELFWriter { StringRef Name; uint32_t SectionIndex; uint32_t Order; - - // Support lexicographic sorting. - bool operator<(const ELFSymbolData &RHS) const { - unsigned LHSType = Symbol->getType(); - unsigned RHSType = RHS.Symbol->getType(); - if (LHSType == ELF::STT_SECTION && RHSType != ELF::STT_SECTION) - return false; - if (LHSType != ELF::STT_SECTION && RHSType == ELF::STT_SECTION) - return true; - if (LHSType == ELF::STT_SECTION && RHSType == ELF::STT_SECTION) - return SectionIndex < RHS.SectionIndex; - return Name < RHS.Name; - } }; /// @} @@ -157,7 +144,7 @@ struct ELFWriter { bool is64Bit() const; bool hasRelocationAddend() const; - void align(unsigned Alignment); + uint64_t align(unsigned Alignment); bool maybeWriteCompression(uint64_t Size, SmallVectorImpl &CompressedContents, @@ -207,8 +194,6 @@ public: MCSectionELF *createRelocationSection(MCContext &Ctx, const MCSectionELF &Sec); - const MCSectionELF *createStringTable(MCContext &Ctx); - void writeSectionHeader(const MCAsmLayout &Layout, const SectionIndexMapTy &SectionIndexMap, const SectionOffsetsTy &SectionOffsets); @@ -337,9 +322,10 @@ public: } // end anonymous namespace -void ELFWriter::align(unsigned Alignment) { - uint64_t Padding = offsetToAlignment(W.OS.tell(), Align(Alignment)); - W.OS.write_zeros(Padding); +uint64_t ELFWriter::align(unsigned Alignment) { + uint64_t Offset = W.OS.tell(), NewOffset = alignTo(Offset, Alignment); + W.OS.write_zeros(NewOffset - Offset); + return NewOffset; } unsigned ELFWriter::addToSectionTable(const MCSectionELF *Sec) { @@ -458,7 +444,7 @@ void ELFWriter::writeHeader(const MCAssembler &Asm) { // e_shnum = # of section header ents W.write(0); - // e_shstrndx = Section # of '.shstrtab' + // e_shstrndx = Section # of '.strtab' assert(StringTableIndex < ELF::SHN_LORESERVE); W.write(StringTableIndex); } @@ -619,8 +605,7 @@ void ELFWriter::computeSymbolTable( SymtabSection->setAlignment(is64Bit() ? Align(8) : Align(4)); SymbolTableIndex = addToSectionTable(SymtabSection); - align(SymtabSection->getAlignment()); - uint64_t SecStart = W.OS.tell(); + uint64_t SecStart = align(SymtabSection->getAlignment()); // The first entry is the undefined symbol entry. Writer.writeSymbol(0, 0, 0, 0, 0, 0, false); @@ -985,12 +970,6 @@ void ELFWriter::writeRelocations(const MCAssembler &Asm, } } -const MCSectionELF *ELFWriter::createStringTable(MCContext &Ctx) { - const MCSectionELF *StrtabSection = SectionTable[StringTableIndex - 1]; - StrTabBuilder.write(W.OS); - return StrtabSection; -} - void ELFWriter::writeSection(const SectionIndexMapTy &SectionIndexMap, uint32_t GroupSymbolIndex, uint64_t Offset, uint64_t Size, const MCSectionELF &Section) { @@ -1105,10 +1084,8 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) { if (Mode == DwoOnly && !isDwoSection(Section)) continue; - align(Section.getAlignment()); - // Remember the offset into the file for this section. - uint64_t SecStart = W.OS.tell(); + const uint64_t SecStart = align(Section.getAlignment()); const MCSymbolELF *SignatureSymbol = Section.getGroup(); writeSectionData(Asm, Section, Layout); @@ -1151,10 +1128,8 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) { } for (MCSectionELF *Group : Groups) { - align(Group->getAlignment()); - // Remember the offset into the file for this section. - uint64_t SecStart = W.OS.tell(); + const uint64_t SecStart = align(Group->getAlignment()); const MCSymbol *SignatureSymbol = Group->getGroup(); assert(SignatureSymbol); @@ -1185,10 +1160,8 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) { SectionOffsets); for (MCSectionELF *RelSection : Relocations) { - align(RelSection->getAlignment()); - // Remember the offset into the file for this section. - uint64_t SecStart = W.OS.tell(); + const uint64_t SecStart = align(RelSection->getAlignment()); writeRelocations(Asm, cast(*RelSection->getLinkedToSection())); @@ -1218,15 +1191,11 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) { { uint64_t SecStart = W.OS.tell(); - const MCSectionELF *Sec = createStringTable(Ctx); - uint64_t SecEnd = W.OS.tell(); - SectionOffsets[Sec] = std::make_pair(SecStart, SecEnd); + StrTabBuilder.write(W.OS); + SectionOffsets[StrtabSection] = std::make_pair(SecStart, W.OS.tell()); } - uint64_t NaturalAlignment = is64Bit() ? 8 : 4; - align(NaturalAlignment); - - const uint64_t SectionHeaderOffset = W.OS.tell(); + const uint64_t SectionHeaderOffset = align(is64Bit() ? 8 : 4); // ... then the section header table ... writeSectionHeader(Layout, SectionIndexMap, SectionOffsets); -- 2.7.4