From: James Henderson Date: Tue, 14 May 2019 10:59:04 +0000 (+0000) Subject: [llvm-objcopy] Cache gnu_debuglink's target CRC X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=9a1a8c8d8ed2c11932f282c66cc0ddde6b21a2fd;p=llvm [llvm-objcopy] Cache gnu_debuglink's target CRC .gnu_debuglink section contains information regarding file with debugging symbols, identified by its CRC32. This target file is not intended to ever change or it would invalidate the stored checksum, yet the checksum is calculated over and over again for each of the objects inside the archive, usually hundreds of times. This patch precomputes the CRC32 of the target once and then reuses the value where required, saving lots of redundant I/O. The error message reported should stay the same, although now it might be reported earlier. Reviewed by: jhenderson, jakehehrlich, MaskRay Differential Revision: https://reviews.llvm.org/D61343 Patch by Michal Janiszewski git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@360661 91177308-0d34-0410-b5e6-96231b3b80d8 --- diff --git a/tools/llvm-objcopy/CopyConfig.cpp b/tools/llvm-objcopy/CopyConfig.cpp index 94c0a5bc631..0b0023f52d8 100644 --- a/tools/llvm-objcopy/CopyConfig.cpp +++ b/tools/llvm-objcopy/CopyConfig.cpp @@ -16,6 +16,7 @@ #include "llvm/Support/CommandLine.h" #include "llvm/Support/Compression.h" #include "llvm/Support/Errc.h" +#include "llvm/Support/JamCRC.h" #include "llvm/Support/MemoryBuffer.h" #include "llvm/Support/StringSaver.h" #include @@ -490,6 +491,22 @@ Expected parseObjcopyOptions(ArrayRef ArgsArr) { } Config.AddGnuDebugLink = InputArgs.getLastArgValue(OBJCOPY_add_gnu_debuglink); + // The gnu_debuglink's target is expected to not change or else its CRC would + // become invalidated and get rejected. We can avoid recalculating the + // checksum for every target file inside an archive by precomputing the CRC + // here. This prevents a significant amount of I/O. + if (!Config.AddGnuDebugLink.empty()) { + auto DebugOrErr = MemoryBuffer::getFile(Config.AddGnuDebugLink); + if (!DebugOrErr) + return createFileError(Config.AddGnuDebugLink, DebugOrErr.getError()); + auto Debug = std::move(*DebugOrErr); + JamCRC CRC; + CRC.update( + ArrayRef(Debug->getBuffer().data(), Debug->getBuffer().size())); + // The CRC32 value needs to be complemented because the JamCRC doesn't + // finalize the CRC32 value. + Config.GnuDebugLinkCRC32 = ~CRC.getCRC(); + } Config.BuildIdLinkDir = InputArgs.getLastArgValue(OBJCOPY_build_id_link_dir); if (InputArgs.hasArg(OBJCOPY_build_id_link_input)) Config.BuildIdLinkInput = diff --git a/tools/llvm-objcopy/CopyConfig.h b/tools/llvm-objcopy/CopyConfig.h index 65d1d27e841..7607d3b34a3 100644 --- a/tools/llvm-objcopy/CopyConfig.h +++ b/tools/llvm-objcopy/CopyConfig.h @@ -115,6 +115,8 @@ struct CopyConfig { // Advanced options StringRef AddGnuDebugLink; + // Cached gnu_debuglink's target CRC + uint32_t GnuDebugLinkCRC32; StringRef BuildIdLinkDir; Optional BuildIdLinkInput; Optional BuildIdLinkOutput; diff --git a/tools/llvm-objcopy/ELF/ELFObjcopy.cpp b/tools/llvm-objcopy/ELF/ELFObjcopy.cpp index bed2414559f..27b56f4622d 100644 --- a/tools/llvm-objcopy/ELF/ELFObjcopy.cpp +++ b/tools/llvm-objcopy/ELF/ELFObjcopy.cpp @@ -685,7 +685,8 @@ static Error handleArgs(const CopyConfig &Config, Object &Obj, } if (!Config.AddGnuDebugLink.empty()) - Obj.addSection(Config.AddGnuDebugLink); + Obj.addSection(Config.AddGnuDebugLink, + Config.GnuDebugLinkCRC32); for (const NewSymbolInfo &SI : Config.SymbolsToAdd) { SectionBase *Sec = Obj.findSection(SI.SectionName); diff --git a/tools/llvm-objcopy/ELF/Object.cpp b/tools/llvm-objcopy/ELF/Object.cpp index d66948a0f46..09d6d827465 100644 --- a/tools/llvm-objcopy/ELF/Object.cpp +++ b/tools/llvm-objcopy/ELF/Object.cpp @@ -755,7 +755,7 @@ void Section::initialize(SectionTableRef SecTable) { void Section::finalize() { this->Link = LinkSection ? LinkSection->Index : 0; } -void GnuDebugLinkSection::init(StringRef File, StringRef Data) { +void GnuDebugLinkSection::init(StringRef File) { FileName = sys::path::filename(File); // The format for the .gnu_debuglink starts with the file name and is // followed by a null terminator and then the CRC32 of the file. The CRC32 @@ -770,21 +770,12 @@ void GnuDebugLinkSection::init(StringRef File, StringRef Data) { // establish the order that sections should go in. By using the maximum // possible offset we cause this section to wind up at the end. OriginalOffset = std::numeric_limits::max(); - JamCRC CRC; - CRC.update(ArrayRef(Data.data(), Data.size())); - // The CRC32 value needs to be complemented because the JamCRC dosn't - // finalize the CRC32 value. It also dosn't negate the initial CRC32 value - // but it starts by default at 0xFFFFFFFF which is the complement of zero. - CRC32 = ~CRC.getCRC(); -} - -GnuDebugLinkSection::GnuDebugLinkSection(StringRef File) : FileName(File) { - // Read in the file to compute the CRC of it. - auto DebugOrErr = MemoryBuffer::getFile(File); - if (!DebugOrErr) - error("'" + File + "': " + DebugOrErr.getError().message()); - auto Debug = std::move(*DebugOrErr); - init(File, Debug->getBuffer()); +} + +GnuDebugLinkSection::GnuDebugLinkSection(StringRef File, + uint32_t PrecomputedCRC) + : FileName(File), CRC32(PrecomputedCRC) { + init(File); } template diff --git a/tools/llvm-objcopy/ELF/Object.h b/tools/llvm-objcopy/ELF/Object.h index 54e72d29aba..9298518bcce 100644 --- a/tools/llvm-objcopy/ELF/Object.h +++ b/tools/llvm-objcopy/ELF/Object.h @@ -18,7 +18,6 @@ #include "llvm/MC/StringTableBuilder.h" #include "llvm/Object/ELFObjectFile.h" #include "llvm/Support/FileOutputBuffer.h" -#include "llvm/Support/JamCRC.h" #include #include #include @@ -703,11 +702,11 @@ private: StringRef FileName; uint32_t CRC32; - void init(StringRef File, StringRef Data); + void init(StringRef File); public: // If we add this section from an external source we can use this ctor. - explicit GnuDebugLinkSection(StringRef File); + explicit GnuDebugLinkSection(StringRef File, uint32_t PrecomputedCRC); void accept(SectionVisitor &Visitor) const override; void accept(MutableSectionVisitor &Visitor) override; };