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Simplify the creation of compressed debug sections.

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This is actually fairly simple in the current code layout: Check if we should
compress just before writing out and everything else just works.

This removes the last case in which the object writer was creating a
fragment.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@236267 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Rafael Espindola 2015-04-30 21:51:58 +00:00
parent cdc4c42bac
commit a55dd52dc8
1 changed files with 34 additions and 107 deletions
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141
lib/MC/ELFObjectWriter.cpp
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@ -182,8 +182,6 @@ class ELFObjectWriter : public MCObjectWriter {
support::endian::Writer<support::big>(OS).write(Val);
}
template <typename T> void write(MCDataFragment &F, T Value);
void writeHeader(const MCAssembler &Asm);
void WriteSymbol(SymbolTableWriter &Writer, ELFSymbolData &MSD,
@ -224,8 +222,6 @@ class ELFObjectWriter : public MCObjectWriter {
const MCSectionELF *createRelocationSection(MCAssembler &Asm,
const MCSectionELF &Sec);
void CompressDebugSections(MCAssembler &Asm, MCAsmLayout &Layout);
const MCSectionELF *createSectionHeaderStringTable();
const MCSectionELF *createStringTable(MCContext &Ctx);
@ -236,10 +232,13 @@ class ELFObjectWriter : public MCObjectWriter {
const SectionIndexMapTy &SectionIndexMap,
const SectionOffsetsTy &SectionOffsets);
void writeSectionData(const MCAssembler &Asm, const MCSectionData &SD,
const MCAsmLayout &Layout);
void WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags,
uint64_t Address, uint64_t Offset,
uint64_t Size, uint32_t Link, uint32_t Info,
uint64_t Alignment, uint64_t EntrySize);
uint64_t Address, uint64_t Offset, uint64_t Size,
uint32_t Link, uint32_t Info, uint64_t Alignment,
uint64_t EntrySize);
void writeRelocations(const MCAssembler &Asm, const MCSectionELF &Sec);
@ -267,15 +266,6 @@ unsigned ELFObjectWriter::addToSectionTable(const MCSectionELF *Sec) {
return SectionTable.size();
}
template <typename T> void ELFObjectWriter::write(MCDataFragment &F, T Val) {
if (IsLittleEndian)
Val = support::endian::byte_swap<T, support::little>(Val);
else
Val = support::endian::byte_swap<T, support::big>(Val);
const char *Start = (const char *)&Val;
F.getContents().append(Start, Start + sizeof(T));
}
void SymbolTableWriter::createSymtabShndx() {
if (!ShndxIndexes.empty())
return;
@ -1105,7 +1095,7 @@ ELFObjectWriter::createRelocationSection(MCAssembler &Asm,
static SmallVector<char, 128>
getUncompressedData(const MCAsmLayout &Layout,
MCSectionData::FragmentListType &Fragments) {
const MCSectionData::FragmentListType &Fragments) {
SmallVector<char, 128> UncompressedData;
for (const MCFragment &F : Fragments) {
const SmallVectorImpl<char> *Contents;
@ -1148,104 +1138,43 @@ prependCompressionHeader(uint64_t Size,
return true;
}
// Return a single fragment containing the compressed contents of the whole
// section. Null if the section was not compressed for any reason.
static std::unique_ptr<MCDataFragment>
getCompressedFragment(const MCAsmLayout &Layout,
MCSectionData::FragmentListType &Fragments) {
std::unique_ptr<MCDataFragment> CompressedFragment(new MCDataFragment());
void ELFObjectWriter::writeSectionData(const MCAssembler &Asm,
const MCSectionData &SD,
const MCAsmLayout &Layout) {
const MCSectionELF &Section =
static_cast<const MCSectionELF &>(SD.getSection());
StringRef SectionName = Section.getSectionName();
// Gather the uncompressed data from all the fragments, recording the
// alignment fragment, if seen, and any fixups.
// Compressing debug_frame requires handling alignment fragments which is
// more work (possibly generalizing MCAssembler.cpp:writeFragment to allow
// for writing to arbitrary buffers) for little benefit.
if (!Asm.getContext().getAsmInfo()->compressDebugSections() ||
!SectionName.startswith(".debug_") || SectionName == ".debug_frame") {
Asm.writeSectionData(&SD, Layout);
return;
}
// Gather the uncompressed data from all the fragments.
const MCSectionData::FragmentListType &Fragments = SD.getFragmentList();
SmallVector<char, 128> UncompressedData =
getUncompressedData(Layout, Fragments);
SmallVectorImpl<char> &CompressedContents = CompressedFragment->getContents();
SmallVector<char, 128> CompressedContents;
zlib::Status Success = zlib::compress(
StringRef(UncompressedData.data(), UncompressedData.size()),
CompressedContents);
if (Success != zlib::StatusOK)
return nullptr;
if (!prependCompressionHeader(UncompressedData.size(), CompressedContents))
return nullptr;
return CompressedFragment;
}
typedef DenseMap<const MCSectionData *, std::vector<MCSymbolData *>>
DefiningSymbolMap;
static void UpdateSymbols(const MCAsmLayout &Layout,
const std::vector<MCSymbolData *> &Symbols,
MCFragment &NewFragment) {
for (MCSymbolData *Sym : Symbols) {
Sym->setOffset(Sym->getOffset() +
Layout.getFragmentOffset(Sym->getFragment()));
Sym->setFragment(&NewFragment);
}
}
static void CompressDebugSection(MCAssembler &Asm, MCAsmLayout &Layout,
const DefiningSymbolMap &DefiningSymbols,
const MCSectionELF &Section,
MCSectionData &SD) {
StringRef SectionName = Section.getSectionName();
MCSectionData::FragmentListType &Fragments = SD.getFragmentList();
std::unique_ptr<MCDataFragment> CompressedFragment =
getCompressedFragment(Layout, Fragments);
// Leave the section as-is if the fragments could not be compressed.
if (!CompressedFragment)
if (Success != zlib::StatusOK) {
Asm.writeSectionData(&SD, Layout);
return;
}
// Update the fragment+offsets of any symbols referring to fragments in this
// section to refer to the new fragment.
auto I = DefiningSymbols.find(&SD);
if (I != DefiningSymbols.end())
UpdateSymbols(Layout, I->second, *CompressedFragment);
// Invalidate the layout for the whole section since it will have new and
// different fragments now.
Layout.invalidateFragmentsFrom(&Fragments.front());
Fragments.clear();
// Complete the initialization of the new fragment
CompressedFragment->setParent(&SD);
CompressedFragment->setLayoutOrder(0);
Fragments.push_back(CompressedFragment.release());
// Rename from .debug_* to .zdebug_*
if (!prependCompressionHeader(UncompressedData.size(), CompressedContents)) {
Asm.writeSectionData(&SD, Layout);
return;
}
Asm.getContext().renameELFSection(&Section,
(".z" + SectionName.drop_front(1)).str());
}
void ELFObjectWriter::CompressDebugSections(MCAssembler &Asm,
MCAsmLayout &Layout) {
if (!Asm.getContext().getAsmInfo()->compressDebugSections())
return;
DefiningSymbolMap DefiningSymbols;
for (MCSymbolData &SD : Asm.symbols())
if (MCFragment *F = SD.getFragment())
DefiningSymbols[F->getParent()].push_back(&SD);
for (MCSectionData &SD : Asm) {
const MCSectionELF &Section =
static_cast<const MCSectionELF &>(SD.getSection());
StringRef SectionName = Section.getSectionName();
// Compressing debug_frame requires handling alignment fragments which is
// more work (possibly generalizing MCAssembler.cpp:writeFragment to allow
// for writing to arbitrary buffers) for little benefit.
if (!SectionName.startswith(".debug_") || SectionName == ".debug_frame")
continue;
CompressDebugSection(Asm, Layout, DefiningSymbols, Section, SD);
}
OS << CompressedContents;
}
void ELFObjectWriter::WriteSecHdrEntry(uint32_t Name, uint32_t Type,
@ -1408,8 +1337,6 @@ void ELFObjectWriter::writeSectionHeader(
void ELFObjectWriter::WriteObject(MCAssembler &Asm,
const MCAsmLayout &Layout) {
CompressDebugSections(Asm, const_cast<MCAsmLayout &>(Layout));
MCContext &Ctx = Asm.getContext();
const MCSectionELF *ShstrtabSection =
Ctx.getELFSection(".shstrtab", ELF::SHT_STRTAB, 0);
@ -1453,7 +1380,7 @@ void ELFObjectWriter::WriteObject(MCAssembler &Asm,
}
writeRelocations(Asm, *Section.getAssociatedSection());
} else {
Asm.writeSectionData(&SD, Layout);
writeSectionData(Asm, SD, Layout);
}
uint64_t SecEnd = OS.tell();