[llvm] r270987 - Recommit 270977 - [llvm-mc] - Teach llvm-mc to generate zlib styled compression sections.
David Blaikie via llvm-commits
llvm-commits at lists.llvm.org
Fri May 27 16:52:29 PDT 2016
On Fri, May 27, 2016 at 5:27 AM, George Rimar via llvm-commits <
llvm-commits at lists.llvm.org> wrote:
> Author: grimar
> Date: Fri May 27 07:27:32 2016
> New Revision: 270987
>
> URL: http://llvm.org/viewvc/llvm-project?rev=270987&view=rev
> Log:
> Recommit 270977 - [llvm-mc] - Teach llvm-mc to generate zlib styled
> compression sections.
>
> Fix: updated clang code which was not updated by mistake.
>
> Original commit message:
> [llvm-mc] - Teach llvm-mc to generate zlib styled compression sections.
>
> 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.
>
I take it the default is zlib? Should we keep the default as zlib-gnu given
the lack of available support currently? (perhaps tweak it on any platforms
that are particularly forward - I imagine FreeBSD might have support for
this sooner than the rest, for example (if it's moving to LLD and other
LLVM tools that have/will probably grow support for zlib-gnu compressed
input sections sooner rather than later))
>
> Differential revision: http://reviews.llvm.org/D20676
>
> Modified:
> llvm/trunk/include/llvm/MC/MCAsmInfo.h
> llvm/trunk/include/llvm/MC/MCSectionELF.h
> llvm/trunk/lib/CodeGen/LLVMTargetMachine.cpp
> llvm/trunk/lib/MC/ELFObjectWriter.cpp
> llvm/trunk/lib/MC/MCAsmInfo.cpp
> llvm/trunk/test/MC/ELF/compression.s
> llvm/trunk/tools/llvm-mc/llvm-mc.cpp
>
> Modified: llvm/trunk/include/llvm/MC/MCAsmInfo.h
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/MC/MCAsmInfo.h?rev=270987&r1=270986&r2=270987&view=diff
>
> ==============================================================================
> --- llvm/trunk/include/llvm/MC/MCAsmInfo.h (original)
> +++ llvm/trunk/include/llvm/MC/MCAsmInfo.h Fri May 27 07:27:32 2016
> @@ -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;
> }
>
>
> Modified: llvm/trunk/include/llvm/MC/MCSectionELF.h
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/MC/MCSectionELF.h?rev=270987&r1=270986&r2=270987&view=diff
>
> ==============================================================================
> --- llvm/trunk/include/llvm/MC/MCSectionELF.h (original)
> +++ llvm/trunk/include/llvm/MC/MCSectionELF.h Fri May 27 07:27:32 2016
> @@ -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,
>
> Modified: llvm/trunk/lib/CodeGen/LLVMTargetMachine.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/LLVMTargetMachine.cpp?rev=270987&r1=270986&r2=270987&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/LLVMTargetMachine.cpp (original)
> +++ llvm/trunk/lib/CodeGen/LLVMTargetMachine.cpp Fri May 27 07:27:32 2016
> @@ -71,7 +71,7 @@ void LLVMTargetMachine::initAsmInfo() {
> TmpAsmInfo->setUseIntegratedAssembler(false);
>
> if (Options.CompressDebugSections)
> - TmpAsmInfo->setCompressDebugSections(true);
> +
> TmpAsmInfo->setCompressDebugSections(DebugCompressionType::DCT_ZlibGnu);
>
> AsmInfo = TmpAsmInfo;
> }
>
> Modified: llvm/trunk/lib/MC/ELFObjectWriter.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/ELFObjectWriter.cpp?rev=270987&r1=270986&r2=270987&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/MC/ELFObjectWriter.cpp (original)
> +++ llvm/trunk/lib/MC/ELFObjectWriter.cpp Fri May 27 07:27:32 2016
> @@ -136,6 +136,10 @@ class ELFObjectWriter : public MCObjectW
>
> 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
> 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(c
> // 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(c
> 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;
> }
>
>
> Modified: llvm/trunk/lib/MC/MCAsmInfo.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCAsmInfo.cpp?rev=270987&r1=270986&r2=270987&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/MC/MCAsmInfo.cpp (original)
> +++ llvm/trunk/lib/MC/MCAsmInfo.cpp Fri May 27 07:27:32 2016
> @@ -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() {
>
> Modified: llvm/trunk/test/MC/ELF/compression.s
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/MC/ELF/compression.s?rev=270987&r1=270986&r2=270987&view=diff
>
> ==============================================================================
> --- llvm/trunk/test/MC/ELF/compression.s (original)
> +++ llvm/trunk/test/MC/ELF/compression.s Fri May 27 07:27:32 2016
> @@ -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,"", at progbits
>
>
> Modified: llvm/trunk/tools/llvm-mc/llvm-mc.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/tools/llvm-mc/llvm-mc.cpp?rev=270987&r1=270986&r2=270987&view=diff
>
> ==============================================================================
> --- llvm/trunk/tools/llvm-mc/llvm-mc.cpp (original)
> +++ llvm/trunk/tools/llvm-mc/llvm-mc.cpp Fri May 27 07:27:32 2016
> @@ -52,9 +52,18 @@ OutputFilename("o", cl::desc("Output fil
> 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
>
>
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