[MC] Allow MCObjectWriter's output stream to be swapped out
authorDavid Majnemer <david.majnemer@gmail.com>
Tue, 1 Sep 2015 16:19:03 +0000 (16:19 +0000)
committerDavid Majnemer <david.majnemer@gmail.com>
Tue, 1 Sep 2015 16:19:03 +0000 (16:19 +0000)
There are occasions where it is useful to consider the entirety of the
contents of a section.  For example, compressed debug info needs the
entire section available before it can compress it and write it out.
The compressed debug info scenario was previously implemented by
mirroring the implementation of writeSectionData in the ELFObjectWriter.

Instead, allow the output stream to be swapped on demand.  This lets
callers redirect the output stream to a more convenient location before
it hits the object file.

No functionality change is intended.

Differential Revision: http://reviews.llvm.org/D12509

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@246554 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/MC/MCObjectWriter.h
lib/MC/ELFObjectWriter.cpp
lib/MC/MachObjectWriter.cpp
lib/MC/WinCOFFObjectWriter.cpp

index 2211673efc31e484355113b6996a23ce3803c86d..406831aae810e3531e62e30847bd40bff0f0b132 100644 (file)
@@ -40,14 +40,14 @@ class MCObjectWriter {
   MCObjectWriter(const MCObjectWriter &) = delete;
   void operator=(const MCObjectWriter &) = delete;
 
-protected:
-  raw_pwrite_stream &OS;
+  raw_pwrite_stream *OS;
 
+protected:
   unsigned IsLittleEndian : 1;
 
 protected: // Can only create subclasses.
   MCObjectWriter(raw_pwrite_stream &OS, bool IsLittleEndian)
-      : OS(OS), IsLittleEndian(IsLittleEndian) {}
+      : OS(&OS), IsLittleEndian(IsLittleEndian) {}
 
 public:
   virtual ~MCObjectWriter();
@@ -57,7 +57,8 @@ public:
 
   bool isLittleEndian() const { return IsLittleEndian; }
 
-  raw_ostream &getStream() { return OS; }
+  raw_pwrite_stream &getStream() { return *OS; }
+  void setStream(raw_pwrite_stream &NewOS) { OS = &NewOS; }
 
   /// \name High-Level API
   /// @{
@@ -113,30 +114,30 @@ public:
   /// \name Binary Output
   /// @{
 
-  void write8(uint8_t Value) { OS << char(Value); }
+  void write8(uint8_t Value) { *OS << char(Value); }
 
   void writeLE16(uint16_t Value) {
-    support::endian::Writer<support::little>(OS).write(Value);
+    support::endian::Writer<support::little>(*OS).write(Value);
   }
 
   void writeLE32(uint32_t Value) {
-    support::endian::Writer<support::little>(OS).write(Value);
+    support::endian::Writer<support::little>(*OS).write(Value);
   }
 
   void writeLE64(uint64_t Value) {
-    support::endian::Writer<support::little>(OS).write(Value);
+    support::endian::Writer<support::little>(*OS).write(Value);
   }
 
   void writeBE16(uint16_t Value) {
-    support::endian::Writer<support::big>(OS).write(Value);
+    support::endian::Writer<support::big>(*OS).write(Value);
   }
 
   void writeBE32(uint32_t Value) {
-    support::endian::Writer<support::big>(OS).write(Value);
+    support::endian::Writer<support::big>(*OS).write(Value);
   }
 
   void writeBE64(uint64_t Value) {
-    support::endian::Writer<support::big>(OS).write(Value);
+    support::endian::Writer<support::big>(*OS).write(Value);
   }
 
   void write16(uint16_t Value) {
@@ -164,9 +165,9 @@ public:
     const char Zeros[16] = {0};
 
     for (unsigned i = 0, e = N / 16; i != e; ++i)
-      OS << StringRef(Zeros, 16);
+      *OS << StringRef(Zeros, 16);
 
-    OS << StringRef(Zeros, N % 16);
+    *OS << StringRef(Zeros, N % 16);
   }
 
   void writeBytes(const SmallVectorImpl<char> &ByteVec,
@@ -180,7 +181,7 @@ public:
     assert(
         (ZeroFillSize == 0 || Str.size() <= ZeroFillSize) &&
         "data size greater than fill size, unexpected large write will occur");
-    OS << Str;
+    *OS << Str;
     if (ZeroFillSize)
       WriteZeros(ZeroFillSize - Str.size());
   }
index e925bc272dc8a3ae1783c38f90cd9e69a72c74e5..16f299c8fd88e27e3572255bea6c0eb9296ef3aa 100644 (file)
@@ -157,9 +157,9 @@ class ELFObjectWriter : public MCObjectWriter {
 
     template <typename T> void write(T Val) {
       if (IsLittleEndian)
-        support::endian::Writer<support::little>(OS).write(Val);
+        support::endian::Writer<support::little>(getStream()).write(Val);
       else
-        support::endian::Writer<support::big>(OS).write(Val);
+        support::endian::Writer<support::big>(getStream()).write(Val);
     }
 
     void writeHeader(const MCAssembler &Asm);
@@ -232,7 +232,7 @@ class ELFObjectWriter : public MCObjectWriter {
 }
 
 void ELFObjectWriter::align(unsigned Alignment) {
-  uint64_t Padding = OffsetToAlignment(OS.tell(), Alignment);
+  uint64_t Padding = OffsetToAlignment(getStream().tell(), Alignment);
   WriteZeros(Padding);
 }
 
@@ -764,7 +764,7 @@ void ELFObjectWriter::computeSymbolTable(
   SymbolTableIndex = addToSectionTable(SymtabSection);
 
   align(SymtabSection->getAlignment());
-  uint64_t SecStart = OS.tell();
+  uint64_t SecStart = getStream().tell();
 
   // The first entry is the undefined symbol entry.
   Writer.writeSymbol(0, 0, 0, 0, 0, 0, false);
@@ -911,7 +911,7 @@ void ELFObjectWriter::computeSymbolTable(
     assert(MSD.Symbol->getBinding() != ELF::STB_LOCAL);
   }
 
-  uint64_t SecEnd = OS.tell();
+  uint64_t SecEnd = getStream().tell();
   SectionOffsets[SymtabSection] = std::make_pair(SecStart, SecEnd);
 
   ArrayRef<uint32_t> ShndxIndexes = Writer.getShndxIndexes();
@@ -921,12 +921,12 @@ void ELFObjectWriter::computeSymbolTable(
   }
   assert(SymtabShndxSectionIndex != 0);
 
-  SecStart = OS.tell();
+  SecStart = getStream().tell();
   const MCSectionELF *SymtabShndxSection =
       SectionTable[SymtabShndxSectionIndex - 1];
   for (uint32_t Index : ShndxIndexes)
     write(Index);
-  SecEnd = OS.tell();
+  SecEnd = getStream().tell();
   SectionOffsets[SymtabShndxSection] = std::make_pair(SecStart, SecEnd);
 }
 
@@ -957,31 +957,6 @@ ELFObjectWriter::createRelocationSection(MCContext &Ctx,
   return RelaSection;
 }
 
-static SmallVector<char, 128>
-getUncompressedData(const MCAsmLayout &Layout,
-                    const MCSection::FragmentListType &Fragments) {
-  SmallVector<char, 128> UncompressedData;
-  for (const MCFragment &F : Fragments) {
-    const SmallVectorImpl<char> *Contents;
-    switch (F.getKind()) {
-    case MCFragment::FT_Data:
-      Contents = &cast<MCDataFragment>(F).getContents();
-      break;
-    case MCFragment::FT_Dwarf:
-      Contents = &cast<MCDwarfLineAddrFragment>(F).getContents();
-      break;
-    case MCFragment::FT_DwarfFrame:
-      Contents = &cast<MCDwarfCallFrameFragment>(F).getContents();
-      break;
-    default:
-      llvm_unreachable(
-          "Not expecting any other fragment types in a debug_* section");
-    }
-    UncompressedData.append(Contents->begin(), Contents->end());
-  }
-  return UncompressedData;
-}
-
 // Include the debug info compression header:
 // "ZLIB" followed by 8 bytes representing the uncompressed size of the section,
 // useful for consumers to preallocate a buffer to decompress into.
@@ -1016,27 +991,29 @@ void ELFObjectWriter::writeSectionData(const MCAssembler &Asm, MCSection &Sec,
     return;
   }
 
-  // Gather the uncompressed data from all the fragments.
-  const MCSection::FragmentListType &Fragments = Section.getFragmentList();
-  SmallVector<char, 128> UncompressedData =
-      getUncompressedData(Layout, Fragments);
+  SmallVector<char, 128> UncompressedData;
+  raw_svector_ostream VecOS(UncompressedData);
+  raw_pwrite_stream &OldStream = getStream();
+  setStream(VecOS);
+  Asm.writeSectionData(&Section, Layout);
+  setStream(OldStream);
 
   SmallVector<char, 128> CompressedContents;
   zlib::Status Success = zlib::compress(
       StringRef(UncompressedData.data(), UncompressedData.size()),
       CompressedContents);
   if (Success != zlib::StatusOK) {
-    Asm.writeSectionData(&Section, Layout);
+    getStream() << UncompressedData;
     return;
   }
 
   if (!prependCompressionHeader(UncompressedData.size(), CompressedContents)) {
-    Asm.writeSectionData(&Section, Layout);
+    getStream() << UncompressedData;
     return;
   }
   Asm.getContext().renameELFSection(&Section,
                                     (".z" + SectionName.drop_front(1)).str());
-  OS << CompressedContents;
+  getStream() << CompressedContents;
 }
 
 void ELFObjectWriter::WriteSecHdrEntry(uint32_t Name, uint32_t Type,
@@ -1100,7 +1077,7 @@ void ELFObjectWriter::writeRelocations(const MCAssembler &Asm,
 
 const MCSectionELF *ELFObjectWriter::createStringTable(MCContext &Ctx) {
   const MCSectionELF *StrtabSection = SectionTable[StringTableIndex - 1];
-  OS << StrTabBuilder.data();
+  getStream() << StrTabBuilder.data();
   return StrtabSection;
 }
 
@@ -1209,12 +1186,12 @@ void ELFObjectWriter::writeObject(MCAssembler &Asm,
     align(Section.getAlignment());
 
     // Remember the offset into the file for this section.
-    uint64_t SecStart = OS.tell();
+    uint64_t SecStart = getStream().tell();
 
     const MCSymbolELF *SignatureSymbol = Section.getGroup();
     writeSectionData(Asm, Section, Layout);
 
-    uint64_t SecEnd = OS.tell();
+    uint64_t SecEnd = getStream().tell();
     SectionOffsets[&Section] = std::make_pair(SecStart, SecEnd);
 
     MCSectionELF *RelSection = createRelocationSection(Ctx, Section);
@@ -1246,7 +1223,7 @@ void ELFObjectWriter::writeObject(MCAssembler &Asm,
     align(Group->getAlignment());
 
     // Remember the offset into the file for this section.
-    uint64_t SecStart = OS.tell();
+    uint64_t SecStart = getStream().tell();
 
     const MCSymbol *SignatureSymbol = Group->getGroup();
     assert(SignatureSymbol);
@@ -1256,7 +1233,7 @@ void ELFObjectWriter::writeObject(MCAssembler &Asm,
       write(SecIndex);
     }
 
-    uint64_t SecEnd = OS.tell();
+    uint64_t SecEnd = getStream().tell();
     SectionOffsets[Group] = std::make_pair(SecStart, SecEnd);
   }
 
@@ -1267,25 +1244,25 @@ void ELFObjectWriter::writeObject(MCAssembler &Asm,
     align(RelSection->getAlignment());
 
     // Remember the offset into the file for this section.
-    uint64_t SecStart = OS.tell();
+    uint64_t SecStart = getStream().tell();
 
     writeRelocations(Asm, *RelSection->getAssociatedSection());
 
-    uint64_t SecEnd = OS.tell();
+    uint64_t SecEnd = getStream().tell();
     SectionOffsets[RelSection] = std::make_pair(SecStart, SecEnd);
   }
 
   {
-    uint64_t SecStart = OS.tell();
+    uint64_t SecStart = getStream().tell();
     const MCSectionELF *Sec = createStringTable(Ctx);
-    uint64_t SecEnd = OS.tell();
+    uint64_t SecEnd = getStream().tell();
     SectionOffsets[Sec] = std::make_pair(SecStart, SecEnd);
   }
 
   uint64_t NaturalAlignment = is64Bit() ? 8 : 4;
   align(NaturalAlignment);
 
-  const unsigned SectionHeaderOffset = OS.tell();
+  const unsigned SectionHeaderOffset = getStream().tell();
 
   // ... then the section header table ...
   writeSectionHeader(Layout, SectionIndexMap, SectionOffsets);
@@ -1301,19 +1278,19 @@ void ELFObjectWriter::writeObject(MCAssembler &Asm,
     uint64_t Val = SectionHeaderOffset;
     if (sys::IsLittleEndianHost != IsLittleEndian)
       sys::swapByteOrder(Val);
-    OS.pwrite(reinterpret_cast<char *>(&Val), sizeof(Val),
-              offsetof(ELF::Elf64_Ehdr, e_shoff));
+    getStream().pwrite(reinterpret_cast<char *>(&Val), sizeof(Val),
+                       offsetof(ELF::Elf64_Ehdr, e_shoff));
     NumSectionsOffset = offsetof(ELF::Elf64_Ehdr, e_shnum);
   } else {
     uint32_t Val = SectionHeaderOffset;
     if (sys::IsLittleEndianHost != IsLittleEndian)
       sys::swapByteOrder(Val);
-    OS.pwrite(reinterpret_cast<char *>(&Val), sizeof(Val),
-              offsetof(ELF::Elf32_Ehdr, e_shoff));
+    getStream().pwrite(reinterpret_cast<char *>(&Val), sizeof(Val),
+                       offsetof(ELF::Elf32_Ehdr, e_shoff));
     NumSectionsOffset = offsetof(ELF::Elf32_Ehdr, e_shnum);
   }
-  OS.pwrite(reinterpret_cast<char *>(&NumSections), sizeof(NumSections),
-            NumSectionsOffset);
+  getStream().pwrite(reinterpret_cast<char *>(&NumSections),
+                     sizeof(NumSections), NumSectionsOffset);
 }
 
 bool ELFObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(
index 59565e289787ee23c4f360d3386b94fc7821cf67..b9ab6c12a47a2b8f3e3700ab188843b72127681b 100644 (file)
@@ -129,7 +129,7 @@ void MachObjectWriter::writeHeader(MachO::HeaderFileType Type,
   // struct mach_header (28 bytes) or
   // struct mach_header_64 (32 bytes)
 
-  uint64_t Start = OS.tell();
+  uint64_t Start = getStream().tell();
   (void) Start;
 
   write32(is64Bit() ? MachO::MH_MAGIC_64 : MachO::MH_MAGIC);
@@ -144,8 +144,9 @@ void MachObjectWriter::writeHeader(MachO::HeaderFileType Type,
   if (is64Bit())
     write32(0); // reserved
 
-  assert(OS.tell() - Start ==
-         (is64Bit()?sizeof(MachO::mach_header_64): sizeof(MachO::mach_header)));
+  assert(
+      getStream().tell() - Start ==
+      (is64Bit() ? sizeof(MachO::mach_header_64) : sizeof(MachO::mach_header)));
 }
 
 /// writeSegmentLoadCommand - Write a segment load command.
@@ -159,7 +160,7 @@ void MachObjectWriter::writeSegmentLoadCommand(
   // struct segment_command (56 bytes) or
   // struct segment_command_64 (72 bytes)
 
-  uint64_t Start = OS.tell();
+  uint64_t Start = getStream().tell();
   (void) Start;
 
   unsigned SegmentLoadCommandSize =
@@ -190,7 +191,7 @@ void MachObjectWriter::writeSegmentLoadCommand(
   write32(NumSections);
   write32(0); // flags
 
-  assert(OS.tell() - Start == SegmentLoadCommandSize);
+  assert(getStream().tell() - Start == SegmentLoadCommandSize);
 }
 
 void MachObjectWriter::writeSection(const MCAsmLayout &Layout,
@@ -210,7 +211,7 @@ void MachObjectWriter::writeSection(const MCAsmLayout &Layout,
   // struct section (68 bytes) or
   // struct section_64 (80 bytes)
 
-  uint64_t Start = OS.tell();
+  uint64_t Start = getStream().tell();
   (void) Start;
 
   writeBytes(Section.getSectionName(), 16);
@@ -234,8 +235,8 @@ void MachObjectWriter::writeSection(const MCAsmLayout &Layout,
   if (is64Bit())
     write32(0); // reserved3
 
-  assert(OS.tell() - Start == (is64Bit() ? sizeof(MachO::section_64) :
-                               sizeof(MachO::section)));
+  assert(getStream().tell() - Start ==
+         (is64Bit() ? sizeof(MachO::section_64) : sizeof(MachO::section)));
 }
 
 void MachObjectWriter::writeSymtabLoadCommand(uint32_t SymbolOffset,
@@ -244,7 +245,7 @@ void MachObjectWriter::writeSymtabLoadCommand(uint32_t SymbolOffset,
                                               uint32_t StringTableSize) {
   // struct symtab_command (24 bytes)
 
-  uint64_t Start = OS.tell();
+  uint64_t Start = getStream().tell();
   (void) Start;
 
   write32(MachO::LC_SYMTAB);
@@ -254,7 +255,7 @@ void MachObjectWriter::writeSymtabLoadCommand(uint32_t SymbolOffset,
   write32(StringTableOffset);
   write32(StringTableSize);
 
-  assert(OS.tell() - Start == sizeof(MachO::symtab_command));
+  assert(getStream().tell() - Start == sizeof(MachO::symtab_command));
 }
 
 void MachObjectWriter::writeDysymtabLoadCommand(uint32_t FirstLocalSymbol,
@@ -267,7 +268,7 @@ void MachObjectWriter::writeDysymtabLoadCommand(uint32_t FirstLocalSymbol,
                                                 uint32_t NumIndirectSymbols) {
   // struct dysymtab_command (80 bytes)
 
-  uint64_t Start = OS.tell();
+  uint64_t Start = getStream().tell();
   (void) Start;
 
   write32(MachO::LC_DYSYMTAB);
@@ -291,7 +292,7 @@ void MachObjectWriter::writeDysymtabLoadCommand(uint32_t FirstLocalSymbol,
   write32(0); // locreloff
   write32(0); // nlocrel
 
-  assert(OS.tell() - Start == sizeof(MachO::dysymtab_command));
+  assert(getStream().tell() - Start == sizeof(MachO::dysymtab_command));
 }
 
 MachObjectWriter::MachSymbolData *
@@ -387,7 +388,7 @@ void MachObjectWriter::writeNlist(MachSymbolData &MSD,
 void MachObjectWriter::writeLinkeditLoadCommand(uint32_t Type,
                                                 uint32_t DataOffset,
                                                 uint32_t DataSize) {
-  uint64_t Start = OS.tell();
+  uint64_t Start = getStream().tell();
   (void) Start;
 
   write32(Type);
@@ -395,7 +396,7 @@ void MachObjectWriter::writeLinkeditLoadCommand(uint32_t Type,
   write32(DataOffset);
   write32(DataSize);
 
-  assert(OS.tell() - Start == sizeof(MachO::linkedit_data_command));
+  assert(getStream().tell() - Start == sizeof(MachO::linkedit_data_command));
 }
 
 static unsigned ComputeLinkerOptionsLoadCommandSize(
@@ -411,7 +412,7 @@ void MachObjectWriter::writeLinkerOptionsLoadCommand(
   const std::vector<std::string> &Options)
 {
   unsigned Size = ComputeLinkerOptionsLoadCommandSize(Options, is64Bit());
-  uint64_t Start = OS.tell();
+  uint64_t Start = getStream().tell();
   (void) Start;
 
   write32(MachO::LC_LINKER_OPTION);
@@ -427,7 +428,7 @@ void MachObjectWriter::writeLinkerOptionsLoadCommand(
   // Pad to a multiple of the pointer size.
   writeBytes("", OffsetToAlignment(BytesWritten, is64Bit() ? 8 : 4));
 
-  assert(OS.tell() - Start == Size);
+  assert(getStream().tell() - Start == Size);
 }
 
 void MachObjectWriter::recordRelocation(MCAssembler &Asm,
@@ -906,12 +907,12 @@ void MachObjectWriter::writeObject(MCAssembler &Asm,
   // Write out the loh commands, if there is one.
   if (LOHSize) {
 #ifndef NDEBUG
-    unsigned Start = OS.tell();
+    unsigned Start = getStream().tell();
 #endif
     Asm.getLOHContainer().emit(*this, Layout);
     // Pad to a multiple of the pointer size.
     writeBytes("", OffsetToAlignment(LOHRawSize, is64Bit() ? 8 : 4));
-    assert(OS.tell() - Start == LOHSize);
+    assert(getStream().tell() - Start == LOHSize);
   }
 
   // Write the symbol table data, if used.
@@ -947,7 +948,7 @@ void MachObjectWriter::writeObject(MCAssembler &Asm,
         writeNlist(Entry, Layout);
 
     // Write the string table.
-    OS << StringTable.data();
+    getStream() << StringTable.data();
   }
 }
 
index 56ef1c7a2735d2fcf3c979c5b77d163c04cc329f..a0a11d42111d15071e3e7491c0a1ca338a932206 100644 (file)
@@ -1037,10 +1037,11 @@ void WinCOFFObjectWriter::writeObject(MCAssembler &Asm,
         continue;
 
       if ((*i)->Header.PointerToRawData != 0) {
-        assert(OS.tell() <= (*i)->Header.PointerToRawData &&
+        assert(getStream().tell() <= (*i)->Header.PointerToRawData &&
                "Section::PointerToRawData is insane!");
 
-        unsigned SectionDataPadding = (*i)->Header.PointerToRawData - OS.tell();
+        unsigned SectionDataPadding =
+            (*i)->Header.PointerToRawData - getStream().tell();
         assert(SectionDataPadding < 4 &&
                "Should only need at most three bytes of padding!");
 
@@ -1050,7 +1051,7 @@ void WinCOFFObjectWriter::writeObject(MCAssembler &Asm,
       }
 
       if ((*i)->Relocations.size() > 0) {
-        assert(OS.tell() == (*i)->Header.PointerToRelocations &&
+        assert(getStream().tell() == (*i)->Header.PointerToRelocations &&
                "Section::PointerToRelocations is insane!");
 
         if ((*i)->Relocations.size() >= 0xffff) {
@@ -1071,14 +1072,14 @@ void WinCOFFObjectWriter::writeObject(MCAssembler &Asm,
     }
   }
 
-  assert(OS.tell() == Header.PointerToSymbolTable &&
+  assert(getStream().tell() == Header.PointerToSymbolTable &&
          "Header::PointerToSymbolTable is insane!");
 
   for (auto &Symbol : Symbols)
     if (Symbol->getIndex() != -1)
       WriteSymbol(*Symbol);
 
-  OS.write(Strings.data().data(), Strings.data().size());
+  getStream().write(Strings.data().data(), Strings.data().size());
 }
 
 MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_)