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Remove zlibgnu support in llvm-mc
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The feature's been removed from most other tools in LLVM at this point.
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@dwblaikie
dwblaikie committed Jul 14, 2022
1 parent 6ab7307 commit d63ec44
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Showing 3 changed files with 45 additions and 79 deletions.
49 changes: 19 additions & 30 deletions llvm/lib/MC/ELFObjectWriter.cpp
View file
Expand Up @@ -146,7 +146,7 @@ struct ELFWriter {

bool maybeWriteCompression(uint64_t Size,
SmallVectorImpl<uint8_t> &CompressedContents,
bool ZLibStyle, unsigned Alignment);
unsigned Alignment);

public:
ELFWriter(ELFObjectWriter &OWriter, raw_pwrite_stream &OS,
Expand Down Expand Up @@ -819,36 +819,25 @@ MCSectionELF *ELFWriter::createRelocationSection(MCContext &Ctx,

// Include the debug info compression header.
bool ELFWriter::maybeWriteCompression(
uint64_t Size, SmallVectorImpl<uint8_t> &CompressedContents, bool ZLibStyle,
uint64_t Size, SmallVectorImpl<uint8_t> &CompressedContents,
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())
uint64_t HdrSize =
is64Bit() ? sizeof(ELF::Elf32_Chdr) : sizeof(ELF::Elf64_Chdr);
if (Size <= HdrSize + CompressedContents.size())
return false;
W.OS << Magic;
support::endian::write(W.OS, Size, support::big);
// 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;
}

Expand Down Expand Up @@ -883,7 +872,7 @@ void ELFWriter::writeSectionData(const MCAssembler &Asm, MCSection &Sec,

bool ZlibStyle = MAI->compressDebugSections() == DebugCompressionType::Z;
if (!maybeWriteCompression(UncompressedData.size(), CompressedContents,
ZlibStyle, Sec.getAlignment())) {
Sec.getAlignment())) {
W.OS << UncompressedData;
return;
}
Expand Down
71 changes: 25 additions & 46 deletions llvm/test/MC/ELF/compression.s
View file
@@ -1,69 +1,48 @@
// REQUIRES: zlib
// 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-str %t | FileCheck --check-prefix=STR %s
// RUN: llvm-mc -filetype=obj -compress-debug-sections=zlib-gnu -triple i386-pc-linux-gnu --defsym I386=1 %s \
// RUN: | llvm-readelf -s - | 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-objdump -s %t | FileCheck %s
// RUN: llvm-dwarfdump -debug-str %t | FileCheck --check-prefix=STR %s
// RUN: llvm-readelf --sections %t | FileCheck --check-prefixes=ZLIB-FLAGS,ZLIB-FLAGS64 %s
// RUN: llvm-readelf --sections %t | FileCheck --check-prefixes=FLAGS,FLAGS64 %s

// RUN: llvm-mc -filetype=obj -compress-debug-sections=zlib -triple i386-pc-linux-gnu --defsym I386=1 %s -o %t
// RUN: llvm-readelf -S -s %t | FileCheck --check-prefixes=386-SYMBOLS-ZLIB,ZLIB-FLAGS,ZLIB-FLAGS32 %s

// Don't compress small sections, such as this simple debug_abbrev example
// CHECK-GNU-STYLE: Contents of section .debug_abbrev:
// CHECK-GNU-STYLE-NOT: ZLIB
// CHECK-GNU-STYLE-NOT: Contents of

// CHECK-GNU-STYLE: Contents of section .debug_info:

// CHECK-GNU-STYLE: Contents of section .zdebug_str:
// Check for the 'ZLIB' file magic at the start of the section only
// CHECK-GNU-STYLE-NEXT: ZLIB
// CHECK-GNU-STYLE-NOT: ZLIB
// CHECK-GNU-STYLE: Contents of section
// RUN: llvm-readelf -S -s %t | FileCheck --check-prefixes=386-SYMBOLS,FLAGS,FLAGS32 %s

// Decompress one valid dwarf section just to check that this roundtrips,
// we use .zdebug_str section for that
// we use .debug_str section for that
// STR: perfectly compressable data sample *****************************************


// 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:
// CHECK: Contents of section .debug_abbrev:
// CHECK-NOT: ZLIB
// CHECK-NOT: Contents of
// CHECK: 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: Contents of section .debug_frame:
// CHECK-NOT: ZLIB
// CHECK: Contents of

# ZLIB-FLAGS: .text PROGBITS [[#%x,]] [[#%x,]] [[#%x,]] 00 AX 0 0 4
# ZLIB-FLAGS: .nonalloc PROGBITS [[#%x,]] [[#%x,]] 000226 00 0 0 1
# FLAGS: .text PROGBITS [[#%x,]] [[#%x,]] [[#%x,]] 00 AX 0 0 4
# FLAGS: .nonalloc PROGBITS [[#%x,]] [[#%x,]] 000226 00 0 0 1

## Check that the large .debug_line and .debug_frame have the SHF_COMPRESSED
## flag.
# ZLIB-FLAGS32: .debug_line PROGBITS [[#%x,]] [[#%x,]] [[#%x,]] 00 C 0 0 4
# ZLIB-FLAGS32: .debug_abbrev PROGBITS [[#%x,]] [[#%x,]] [[#%x,]] 00 0 0 1
# ZLIB-FLAGS32: .debug_info PROGBITS [[#%x,]] [[#%x,]] [[#%x,]] 00 0 0 1
# ZLIB-FLAGS32: .debug_frame PROGBITS [[#%x,]] [[#%x,]] [[#%x,]] 00 C 0 0 4

# ZLIB-FLAGS64: .debug_line PROGBITS [[#%x,]] [[#%x,]] [[#%x,]] 00 C 0 0 8
# ZLIB-FLAGS64: .debug_abbrev PROGBITS [[#%x,]] [[#%x,]] [[#%x,]] 00 0 0 1
# ZLIB-FLAGS64: .debug_info PROGBITS [[#%x,]] [[#%x,]] [[#%x,]] 00 0 0 1
# ZLIB-FLAGS64: .debug_frame PROGBITS [[#%x,]] [[#%x,]] [[#%x,]] 00 C 0 0 8

# 386-SYMBOLS-ZLIB: Symbol table '.symtab'
# 386-SYMBOLS-ZLIB: .debug_str
# 386-SYMBOLS-GNU: Symbol table '.symtab'
# 386-SYMBOLS-GNU: .zdebug_str
# FLAGS32: .debug_line PROGBITS [[#%x,]] [[#%x,]] [[#%x,]] 00 C 0 0 4
# FLAGS32: .debug_abbrev PROGBITS [[#%x,]] [[#%x,]] [[#%x,]] 00 0 0 1
# FLAGS32: .debug_info PROGBITS [[#%x,]] [[#%x,]] [[#%x,]] 00 0 0 1
# FLAGS32: .debug_frame PROGBITS [[#%x,]] [[#%x,]] [[#%x,]] 00 C 0 0 4

# FLAGS64: .debug_line PROGBITS [[#%x,]] [[#%x,]] [[#%x,]] 00 C 0 0 8
# FLAGS64: .debug_abbrev PROGBITS [[#%x,]] [[#%x,]] [[#%x,]] 00 0 0 1
# FLAGS64: .debug_info PROGBITS [[#%x,]] [[#%x,]] [[#%x,]] 00 0 0 1
# FLAGS64: .debug_frame PROGBITS [[#%x,]] [[#%x,]] [[#%x,]] 00 C 0 0 8

# 386-SYMBOLS: Symbol table '.symtab'
# 386-SYMBOLS: .debug_str

## Don't compress a section not named .debug_*.
.section .nonalloc,"",@progbits
Expand Down
4 changes: 1 addition & 3 deletions llvm/tools/llvm-mc/llvm-mc.cpp
View file
Expand Up @@ -77,9 +77,7 @@ static cl::opt<DebugCompressionType> CompressDebugSections(
cl::desc("Choose DWARF debug sections compression:"),
cl::values(clEnumValN(DebugCompressionType::None, "none", "No compression"),
clEnumValN(DebugCompressionType::Z, "zlib",
"Use zlib compression"),
clEnumValN(DebugCompressionType::GNU, "zlib-gnu",
"Use zlib-gnu compression (deprecated)")),
"Use zlib compression")),
cl::cat(MCCategory));

static cl::opt<bool>
Expand Down

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