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[llvm-mc] - Teach llvm-mc to generate zlib styled compression sections.

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This patch is strongly based on previously reverted D20331.
(because of gnuutils < 2.26 does not support compressed debug sections in non zlib-gnu style)

Difference that this patch supports both zlib and zlib-gnu styles.

-compress-debug-sections option now supports next values:

-compress-debug-sections=zlib-gnu
-compress-debug-sections=zlib
-compress-debug-sections=none
Previously specifying -compress-debug-sections enabled zlib-gnu compression,
so anyone can put "-compress-debug-sections=zlib-gnu" to restore the behavior
that was before this patch for case when compression was enabled.

Differential revision: http://reviews.llvm.org/D20676

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@270977 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
George Rimar 2016-05-27 09:58:08 +00:00
parent 3808026456
commit dd4101a976
7 changed files with 130 additions and 48 deletions
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16
include/llvm/MC/MCAsmInfo.h
View File

@ -53,6 +53,12 @@ namespace LCOMM {
enum LCOMMType { NoAlignment, ByteAlignment, Log2Alignment };
}
enum class DebugCompressionType {
DCT_None, // no compression
DCT_Zlib, // zlib style complession
DCT_ZlibGnu // zlib-gnu style compression
};
/// This class is intended to be used as a base class for asm
/// properties and features specific to the target.
class MCAsmInfo {
@ -356,8 +362,8 @@ protected:
/// construction (see LLVMTargetMachine::initAsmInfo()).
bool UseIntegratedAssembler;
/// Compress DWARF debug sections. Defaults to false.
bool CompressDebugSections;
/// Compress DWARF debug sections. Defaults to no compression.
DebugCompressionType CompressDebugSections;
/// True if the integrated assembler should interpret 'a >> b' constant
/// expressions as logical rather than arithmetic.
@ -565,9 +571,11 @@ public:
UseIntegratedAssembler = Value;
}
bool compressDebugSections() const { return CompressDebugSections; }
DebugCompressionType compressDebugSections() const {
return CompressDebugSections;
}
void setCompressDebugSections(bool CompressDebugSections) {
void setCompressDebugSections(DebugCompressionType CompressDebugSections) {
this->CompressDebugSections = CompressDebugSections;
}

1
include/llvm/MC/MCSectionELF.h
View File

@ -75,6 +75,7 @@ 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,

2
lib/CodeGen/LLVMTargetMachine.cpp
View File

@ -71,7 +71,7 @@ void LLVMTargetMachine::initAsmInfo() {
TmpAsmInfo->setUseIntegratedAssembler(false);
if (Options.CompressDebugSections)
TmpAsmInfo->setCompressDebugSections(true);
TmpAsmInfo->setCompressDebugSections(DebugCompressionType::DCT_ZlibGnu);
AsmInfo = TmpAsmInfo;
}

69
lib/MC/ELFObjectWriter.cpp
View File

@ -136,6 +136,10 @@ class ELFObjectWriter : public MCObjectWriter {
void align(unsigned Alignment);
bool maybeWriteCompression(uint64_t Size,
SmallVectorImpl<char> &CompressedContents,
bool ZLibStyle, unsigned Alignment);
public:
ELFObjectWriter(MCELFObjectTargetWriter *MOTW, raw_pwrite_stream &OS,
bool IsLittleEndian)
@ -979,23 +983,38 @@ 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) {
// Include the debug info compression header.
bool ELFObjectWriter::maybeWriteCompression(
uint64_t Size, SmallVectorImpl<char> &CompressedContents, bool ZLibStyle,
unsigned Alignment) {
if (ZLibStyle) {
uint64_t HdrSize =
is64Bit() ? sizeof(ELF::Elf32_Chdr) : sizeof(ELF::Elf64_Chdr);
if (Size <= HdrSize + CompressedContents.size())
return false;
// 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>(Size));
write(static_cast<ELF::Elf64_Xword>(Alignment));
} else {
// Write Elf32_Chdr header otherwise.
write(static_cast<ELF::Elf32_Word>(ELF::ELFCOMPRESS_ZLIB));
write(static_cast<ELF::Elf32_Word>(Size));
write(static_cast<ELF::Elf32_Word>(Alignment));
}
return true;
}
// "ZLIB" followed by 8 bytes representing the uncompressed size of the section,
// useful for consumers to preallocate a buffer to decompress into.
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());
write(ArrayRef<char>(Magic.begin(), Magic.size()));
writeBE64(Size);
return true;
}
@ -1007,8 +1026,11 @@ void ELFObjectWriter::writeSectionData(const MCAssembler &Asm, MCSection &Sec,
// 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") {
bool CompressionEnabled =
Asm.getContext().getAsmInfo()->compressDebugSections() !=
DebugCompressionType::DCT_None;
if (!CompressionEnabled || !SectionName.startswith(".debug_") ||
SectionName == ".debug_frame") {
Asm.writeSectionData(&Section, Layout);
return;
}
@ -1029,12 +1051,21 @@ void ELFObjectWriter::writeSectionData(const MCAssembler &Asm, MCSection &Sec,
return;
}
if (!prependCompressionHeader(UncompressedData.size(), CompressedContents)) {
bool ZlibStyle = Asm.getContext().getAsmInfo()->compressDebugSections() ==
DebugCompressionType::DCT_Zlib;
if (!maybeWriteCompression(UncompressedData.size(), CompressedContents,
ZlibStyle, Sec.getAlignment())) {
getStream() << UncompressedData;
return;
}
Asm.getContext().renameELFSection(&Section,
(".z" + SectionName.drop_front(1)).str());
if (ZlibStyle)
// Set the compressed flag. That is zlib style.
Section.setFlags(Section.getFlags() | ELF::SHF_COMPRESSED);
else
// Add "z" prefix to section name. This is zlib-gnu style.
Asm.getContext().renameELFSection(&Section,
(".z" + SectionName.drop_front(1)).str());
getStream() << CompressedContents;
}

2
lib/MC/MCAsmInfo.cpp
View File

@ -108,7 +108,7 @@ MCAsmInfo::MCAsmInfo() {
// - The target subclasses for AArch64, ARM, and X86 handle these cases
UseIntegratedAssembler = false;
CompressDebugSections = false;
CompressDebugSections = DebugCompressionType::DCT_None;
}
MCAsmInfo::~MCAsmInfo() {

69
test/MC/ELF/compression.s
View File

@ -1,27 +1,35 @@
// RUN: llvm-mc -filetype=obj -compress-debug-sections -triple x86_64-pc-linux-gnu < %s -o %t
// RUN: llvm-objdump -s %t | FileCheck %s
// Check zlib-gnu style
// RUN: llvm-mc -filetype=obj -compress-debug-sections=zlib-gnu -triple x86_64-pc-linux-gnu < %s -o %t
// RUN: llvm-objdump -s %t | FileCheck --check-prefix=CHECK-GNU-STYLE %s
// RUN: llvm-dwarfdump -debug-dump=str %t | FileCheck --check-prefix=STR %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-mc -filetype=obj -compress-debug-sections=zlib-gnu -triple i386-pc-linux-gnu < %s \
// RUN: | llvm-readobj -symbols - | FileCheck --check-prefix=386-SYMBOLS-GNU %s
// Check zlib style
// RUN: llvm-mc -filetype=obj -compress-debug-sections=zlib -triple x86_64-pc-linux-gnu < %s -o %t
// RUN: llvm-objdump -s %t | FileCheck --check-prefix=CHECK-ZLIB-STYLE %s
// RUN: llvm-dwarfdump -debug-dump=str %t | FileCheck --check-prefix=STR %s
// RUN: llvm-mc -filetype=obj -compress-debug-sections=zlib -triple i386-pc-linux-gnu < %s \
// RUN: | llvm-readobj -symbols - | FileCheck --check-prefix=386-SYMBOLS-ZLIB %s
// RUN: llvm-readobj -sections %t | FileCheck --check-prefix=ZLIB-STYLE-FLAGS %s
// REQUIRES: zlib
// Don't compress small sections, such as this simple debug_abbrev example
// CHECK: Contents of section .debug_abbrev:
// CHECK-NOT: ZLIB
// CHECK-NOT: Contents of
// CHECK-GNU-STYLE: Contents of section .debug_abbrev:
// CHECK-GNU-STYLE-NOT: ZLIB
// CHECK-GNU-STYLE-NOT: Contents of
// CHECK: Contents of section .debug_info:
// CHECK-GNU-STYLE: Contents of section .debug_info:
// CHECK: Contents of section .zdebug_str:
// CHECK-GNU-STYLE: Contents of section .zdebug_str:
// Check for the 'ZLIB' file magic at the start of the section only
// CHECK-NEXT: ZLIB
// CHECK-NOT: ZLIB
// CHECK-GNU-STYLE-NEXT: ZLIB
// CHECK-GNU-STYLE-NOT: ZLIB
// FIXME: Handle compressing alignment fragments to support compressing debug_frame
// CHECK: Contents of section .debug_frame:
// CHECK-NOT: ZLIB
// CHECK: Contents of
// CHECK-GNU-STYLE: Contents of section .debug_frame:
// CHECK-GNU-STYLE-NOT: ZLIB
// CHECK-GNU-STYLE: Contents of
// Decompress one valid dwarf section just to check that this roundtrips,
// we use .zdebug_str section for that
@ -29,9 +37,34 @@
// In x86 32 bit named symbols are used for temporary symbols in merge
// 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-GNU: Name: .Linfo_string0
// 386-SYMBOLS-GNU-NOT: }
// 386-SYMBOLS-GNU: Section: .zdebug_str
// Now check the zlib style output:
// Don't compress small sections, such as this simple debug_abbrev example
// CHECK-ZLIB-STYLE: Contents of section .debug_abbrev:
// CHECK-ZLIB-STYLE-NOT: ZLIB
// CHECK-ZLIB-STYLE-NOT: Contents of
// CHECK-ZLIB-STYLE: Contents of section .debug_info:
// FIXME: Handle compressing alignment fragments to support compressing debug_frame
// CHECK-ZLIB-STYLE: Contents of section .debug_frame:
// CHECK-ZLIB-STYLE-NOT: ZLIB
// CHECK-ZLIB-STYLE: Contents of
// Check that debug_line section was not renamed, so it is
// zlib-style, not zlib-gnu one. Check that SHF_COMPRESSED was set.
// ZLIB-STYLE-FLAGS: Section {
// ZLIB-STYLE-FLAGS: Index:
// ZLIB-STYLE-FLAGS: Name: .debug_str
// ZLIB-STYLE-FLAGS-NEXT: Type: SHT_PROGBITS
// ZLIB-STYLE-FLAGS-NEXT: Flags [
// ZLIB-STYLE-FLAGS-NEXT: SHF_COMPRESSED
// 386-SYMBOLS-ZLIB: Name: .Linfo_string0
// 386-SYMBOLS-ZLIB-NOT: }
// 386-SYMBOLS-ZLIB: Section: .debug_str
.section .debug_line,"",@progbits

19
tools/llvm-mc/llvm-mc.cpp
View File

@ -52,9 +52,18 @@ OutputFilename("o", cl::desc("Output filename"),
static cl::opt<bool>
ShowEncoding("show-encoding", cl::desc("Show instruction encodings"));
static cl::opt<bool>
CompressDebugSections("compress-debug-sections",
cl::desc("Compress DWARF debug sections"));
static cl::opt<DebugCompressionType>
CompressDebugSections("compress-debug-sections", cl::ValueOptional,
cl::init(DebugCompressionType::DCT_None),
cl::desc("Choose DWARF debug sections compression:"),
cl::values(
clEnumValN(DebugCompressionType::DCT_None, "none",
"No compression"),
clEnumValN(DebugCompressionType::DCT_Zlib, "zlib",
"Use zlib compression"),
clEnumValN(DebugCompressionType::DCT_ZlibGnu, "zlib-gnu",
"Use zlib-gnu compression (depricated)"),
clEnumValEnd));
static cl::opt<bool>
ShowInst("show-inst", cl::desc("Show internal instruction representation"));
@ -407,13 +416,13 @@ int main(int argc, char **argv) {
std::unique_ptr<MCAsmInfo> MAI(TheTarget->createMCAsmInfo(*MRI, TripleName));
assert(MAI && "Unable to create target asm info!");
if (CompressDebugSections) {
if (CompressDebugSections != DebugCompressionType::DCT_None) {
if (!zlib::isAvailable()) {
errs() << ProgName
<< ": build tools with zlib to enable -compress-debug-sections";
return 1;
}
MAI->setCompressDebugSections(true);
MAI->setCompressDebugSections(CompressDebugSections);
}
// FIXME: This is not pretty. MCContext has a ptr to MCObjectFileInfo and