[llvm] r270070 - [llvm-mc] - Teach llvm-mc to generate compressed debug sections in zlib style.
George Rimar via llvm-commits
llvm-commits at lists.llvm.org
Thu May 19 08:08:32 PDT 2016
Author: grimar
Date: Thu May 19 10:08:31 2016
New Revision: 270070
URL: http://llvm.org/viewvc/llvm-project?rev=270070&view=rev
Log:
[llvm-mc] - Teach llvm-mc to generate compressed debug sections in zlib style.
Before this patch llvm-mc generated zlib-gnu styled sections.
That means no SHF_COMPRESSED flag was set, magic 'zlib' signature
was used in combination with full size field. Sections were renamed to "*.z*".
This patch reimplements the compression style to zlib one as zlib-gnu looks
to be depricated everywhere.
Differential revision: http://reviews.llvm.org/D20331
Modified:
llvm/trunk/include/llvm/MC/MCContext.h
llvm/trunk/include/llvm/MC/MCSectionELF.h
llvm/trunk/lib/MC/ELFObjectWriter.cpp
llvm/trunk/lib/MC/MCContext.cpp
llvm/trunk/test/MC/ELF/compression.s
Modified: llvm/trunk/include/llvm/MC/MCContext.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/MC/MCContext.h?rev=270070&r1=270069&r2=270070&view=diff
==============================================================================
--- llvm/trunk/include/llvm/MC/MCContext.h (original)
+++ llvm/trunk/include/llvm/MC/MCContext.h Thu May 19 10:08:31 2016
@@ -385,8 +385,6 @@ namespace llvm {
const MCSymbolELF *Group,
const MCSectionELF *Associated);
- void renameELFSection(MCSectionELF *Section, StringRef Name);
-
MCSectionELF *createELFGroupSection(const MCSymbolELF *Group);
MCSectionCOFF *getCOFFSection(StringRef Section, unsigned Characteristics,
Modified: llvm/trunk/include/llvm/MC/MCSectionELF.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/MC/MCSectionELF.h?rev=270070&r1=270069&r2=270070&view=diff
==============================================================================
--- llvm/trunk/include/llvm/MC/MCSectionELF.h (original)
+++ llvm/trunk/include/llvm/MC/MCSectionELF.h Thu May 19 10:08:31 2016
@@ -62,8 +62,6 @@ private:
Group->setIsSignature();
}
- void setSectionName(StringRef Name) { SectionName = Name; }
-
public:
~MCSectionELF();
@@ -75,6 +73,7 @@ public:
unsigned getType() const { return Type; }
unsigned getFlags() const { return Flags; }
unsigned getEntrySize() const { return EntrySize; }
+ void setFlags(unsigned F) { Flags = F; }
const MCSymbolELF *getGroup() const { return Group; }
void PrintSwitchToSection(const MCAsmInfo &MAI, raw_ostream &OS,
Modified: llvm/trunk/lib/MC/ELFObjectWriter.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/ELFObjectWriter.cpp?rev=270070&r1=270069&r2=270070&view=diff
==============================================================================
--- llvm/trunk/lib/MC/ELFObjectWriter.cpp (original)
+++ llvm/trunk/lib/MC/ELFObjectWriter.cpp Thu May 19 10:08:31 2016
@@ -979,26 +979,6 @@ ELFObjectWriter::createRelocationSection
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(c
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;
}
Modified: llvm/trunk/lib/MC/MCContext.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCContext.cpp?rev=270070&r1=270069&r2=270070&view=diff
==============================================================================
--- llvm/trunk/lib/MC/MCContext.cpp (original)
+++ llvm/trunk/lib/MC/MCContext.cpp Thu May 19 10:08:31 2016
@@ -285,22 +285,6 @@ MCSectionMachO *MCContext::getMachOSecti
Segment, Section, TypeAndAttributes, Reserved2, Kind, Begin);
}
-void MCContext::renameELFSection(MCSectionELF *Section, StringRef Name) {
- StringRef GroupName;
- if (const MCSymbol *Group = Section->getGroup())
- GroupName = Group->getName();
-
- unsigned UniqueID = Section->getUniqueID();
- ELFUniquingMap.erase(
- ELFSectionKey{Section->getSectionName(), GroupName, UniqueID});
- auto I = ELFUniquingMap.insert(std::make_pair(
- ELFSectionKey{Name, GroupName, UniqueID},
- Section))
- .first;
- StringRef CachedName = I->first.SectionName;
- const_cast<MCSectionELF *>(Section)->setSectionName(CachedName);
-}
-
MCSectionELF *MCContext::createELFRelSection(StringRef Name, unsigned Type,
unsigned Flags, unsigned EntrySize,
const MCSymbolELF *Group,
Modified: llvm/trunk/test/MC/ELF/compression.s
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/MC/ELF/compression.s?rev=270070&r1=270069&r2=270070&view=diff
==============================================================================
--- llvm/trunk/test/MC/ELF/compression.s (original)
+++ llvm/trunk/test/MC/ELF/compression.s Thu May 19 10:08:31 2016
@@ -3,13 +3,19 @@
// RUN: llvm-dwarfdump -debug-dump=info %t | FileCheck --check-prefix=INFO %s
// RUN: llvm-mc -filetype=obj -compress-debug-sections -triple i386-pc-linux-gnu < %s \
// RUN: | llvm-readobj -symbols - | FileCheck --check-prefix=386-SYMBOLS %s
+// RUN: llvm-readobj -sections %t | FileCheck --check-prefix=ZLIB %s
// REQUIRES: zlib
-// CHECK: Contents of section .zdebug_line:
-// Check for the 'ZLIB' file magic at the start of the section only
-// CHECK-NEXT: ZLIB
-// CHECK-NOT: ZLIB
+// Check that debug_line section was not renamed, so it is
+// zlib-style, not zlib-gnu one. Check that SHF_COMPRESSED was set.
+// ZLIB: Section {
+// ZLIB: Index:
+// ZLIB: Name: .debug_line
+// ZLIB-NEXT: Type: SHT_PROGBITS
+// ZLIB-NEXT: Flags [
+// ZLIB-NEXT: SHF_COMPRESSED
+// ZLIB-NEXT: ]
// Don't compress small sections, such as this simple debug_abbrev example
// CHECK: Contents of section .debug_abbrev:
@@ -30,7 +36,7 @@
// sections, so make sure we handle symbols inside compressed sections
// 386-SYMBOLS: Name: .Linfo_string0
// 386-SYMBOLS-NOT: }
-// 386-SYMBOLS: Section: .zdebug_str
+// 386-SYMBOLS: Section: .debug_str
.section .debug_line,"", at progbits
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