1 files changed, 21 insertions, 23 deletions

diff --git a/llvm/lib/MC/ELFObjectWriter.cpp b/llvm/lib/MC/ELFObjectWriter.cpp
index 900dcf51a26..7250806167f 100644
--- a/llvm/lib/MC/ELFObjectWriter.cpp
+++ b/llvm/lib/MC/ELFObjectWriter.cpp
@@ -979,26 +979,6 @@ ELFObjectWriter::createRelocationSection(MCContext &Ctx,
   return RelaSection;
 }
 
-// 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.
-static bool
-prependCompressionHeader(uint64_t Size,
-                         SmallVectorImpl<char> &CompressedContents) {
-  const StringRef Magic = "ZLIB";
-  if (Size <= Magic.size() + sizeof(Size) + CompressedContents.size())
-    return false;
-  if (sys::IsLittleEndianHost)
-    sys::swapByteOrder(Size);
-  CompressedContents.insert(CompressedContents.begin(),
-                            Magic.size() + sizeof(Size), 0);
-  std::copy(Magic.begin(), Magic.end(), CompressedContents.begin());
-  std::copy(reinterpret_cast<char *>(&Size),
-            reinterpret_cast<char *>(&Size + 1),
-            CompressedContents.begin() + Magic.size());
-  return true;
-}
-
 void ELFObjectWriter::writeSectionData(const MCAssembler &Asm, MCSection &Sec,
                                        const MCAsmLayout &Layout) {
   MCSectionELF &Section = static_cast<MCSectionELF &>(Sec);
@@ -1029,12 +1009,30 @@ void ELFObjectWriter::writeSectionData(const MCAssembler &Asm, MCSection &Sec,
     return;
   }
 
-  if (!prependCompressionHeader(UncompressedData.size(), CompressedContents)) {
+  uint64_t HdrSize =
+      is64Bit() ? sizeof(ELF::Elf32_Chdr) : sizeof(ELF::Elf64_Chdr);
+  if (UncompressedData.size() <= HdrSize + CompressedContents.size()) {
     getStream() << UncompressedData;
     return;
   }
-  Asm.getContext().renameELFSection(&Section,
-                                    (".z" + SectionName.drop_front(1)).str());
+
+  // Set the compressed flag. That is zlib style.
+  Section.setFlags(Section.getFlags() | ELF::SHF_COMPRESSED);
+
+  // Platform specific header is followed by compressed data.
+  if (is64Bit()) {
+    // Write Elf64_Chdr header.
+    write(static_cast<ELF::Elf64_Word>(ELF::ELFCOMPRESS_ZLIB));
+    write(static_cast<ELF::Elf64_Word>(0)); // ch_reserved field.
+    write(static_cast<ELF::Elf64_Xword>(UncompressedData.size()));
+    write(static_cast<ELF::Elf64_Xword>(Sec.getAlignment()));
+  } else {
+    // Write Elf32_Chdr header otherwise.
+    write(static_cast<ELF::Elf32_Word>(ELF::ELFCOMPRESS_ZLIB));
+    write(static_cast<ELF::Elf32_Word>(UncompressedData.size()));
+    write(static_cast<ELF::Elf32_Word>(Sec.getAlignment()));
+  }
+
   getStream() << CompressedContents;
 }