Handle versioned symbols efficiently.

[ruiu]

Summary

Versions can be assigned to symbols in two different ways.
One is the usual version scripts, and the other is special
symbol suffix '@'. If a symbol contains '@', the string after
that is considered to specify a version name.

Previously, we look for '@' for all symbols.

Anything that works on every symbol can be expensive because
the linker has to handle a lot of symbols. The search for '@'
was not an exception.

In this patch, I made two optimizations.

The first optimization is to handle '@' only when at least one
version is defined. If no versions are defined, no versions can
be assigned to any symbols, so it's waste of time to search for '@'.

The second optimization is to scan only suffixes of symbol names
instead of entire symbol names. Symbol names can be very long, but
symbol versions are usually short, so scanning entire symbol names
is waste of time, too.

There are some error cases which we no longer be able to detect
with this patch. I don't think it's a major drawback because they
are minor errors. Speed is more important.

This change improves LLD with debug info self-link time from
6.6993 seconds to 6.3426 seconds (or -5.3%).

[grimar]

Interesting. What is wierd for me that I think I did perfomance tests that showed that there is no difference with/without the search. (https://reviews.llvm.org/D21681#466406). Since that time I was really sure that search of @ in symbol names is really quick operation.

I also have a little consern about this patch. If I do not missing anything, it should break the https://llvm.org/bugs/show_bug.cgi?id=28359 again ? Not sure do we really want that ?

[ruiu]

No, it won't bring back the issue as this code works only when you pass a version script. I verified that using the reproduce file that Ed posted.

[grimar]

In D22433#486255, @ruiu wrote:

No, it won't bring back the issue as this code works only when you pass a version script. I verified that using the reproduce file that Ed posted.

Right, I see. LGTM with few nits.

ELF/SymbolTable.cpp

598 ↗

(On Diff #64219)

I think return size_t would be more clean.

626 ↗

(On Diff #64219)

This required the next change for me to compile using msvs2015:

for (elf::VersionDefinition &V : Config->VersionDefinitions) {
  if (V.Name == Verstr)
    return{ Name, IsDefault ? V.Id : (V.Id | VERSYM_HIDDEN) };
}

[ruiu]

ELF/SymbolTable.cpp

598 ↗

(On Diff #64219)

I agree, but it's a little bit tricky. At line 609, we are using the result to pass std::max. Since we want to compare the result of the expression against 0, we want to get a signed result. So I avoided using an unsigned value.

[ruiu]

Submitted as r275711. Can you run your benchmark again so that we find what was wrong?

ELF/SymbolTable.cpp

626 ↗

(On Diff #64219)

Fixed.

[grimar]

In D22433#486515, @ruiu wrote:

Submitted as r275711. Can you run your benchmark again so that we find what was wrong?

Sure, I`ll do that tomorrow.

[grimar]

In D22433#486515, @ruiu wrote:

Submitted as r275711. Can you run your benchmark again so that we find what was wrong?

By the way, do you want me to check the latest revision, or (what I guess) to retest the change performed by my patch initially ?

[grimar]

In D22433#486515, @ruiu wrote:

Submitted as r275711. Can you run your benchmark again so that we find what was wrong?

I probably missing something but I can't realize how you have so large numbers like 6-7 seconds in your benchmark.
The last my attemp was:

1. I prepared release lld build. (I suppose you probably used debug build here ?)

2. I configured another build with

-DCMAKE_BUILD_TYPE=RelWithDebInfo -DLLVM_PARALLEL_COMPILE_JOBS=8 -DLLVM_ENABLE_THREADS=true -DCMAKE_CXX_FLAGS="-fPIC -std=c++11 -fuse-ld=lld" -DCMAKE_C_FLAGS="-fPIC -fuse-ld=lld" -DCMAKE_C_COMPILER=/home/umb/LLVM/llvm-build/bin/clang -DCMAKE_CXX_COMPILER=/home/umb/LLVM/llvm-build/bin/clang++
So it uses everything from step 1. And builded it.

3. After that I am trying to just relink the lld configured at step 2 with lld from step 1.

sudo schedtool -F -p 99 -a 0x1 -e perf stat -r 1 /home/umb/LLVM/llvm-build/bin/ld.lld -z relro --hash-style=gnu --eh-frame-hdr -m elf_x86_64 -dynamic-linker /lib64/ld-linux-x86-64.so.2 -o bin/lld /usr/lib/gcc/x86_64-linux-gnu/5.3.1/../../../x86_64-linux-gnu/crt1.o /usr/lib/gcc/x86_64-linux-gnu/5.3.1/../../../x86_64-linux-gnu/crti.o /usr/lib/gcc/x86_64-linux-gnu/5.3.1/crtbegin.o -L/usr/lib/gcc/x86_64-linux-gnu/5.3.1 -L/usr/lib/gcc/x86_64-linux-gnu/5.3.1/../../../x86_64-linux-gnu -L/lib/x86_64-linux-gnu -L/lib/../lib64 -L/usr/lib/x86_64-linux-gnu -L/usr/lib/gcc/x86_64-linux-gnu/5.3.1/../../.. -L/home/umb/LLVM/llvm-build/bin/../lib -L/lib -L/usr/lib -allow-shlib-undefined -O3 --gc-sections tools/lld/tools/lld/CMakeFiles/lld.dir/lld.cpp.o -lpthread lib/liblldDriver.a lib/liblldCOFF.a lib/liblldELF.a lib/libLLVMSupport.a lib/liblldMachO.a lib/liblldReaderWriter.a lib/liblldYAML.a lib/liblldCore.a lib/libLLVMLibDriver.a lib/liblldConfig.a lib/libLLVMOption.a lib/libLLVMAArch64CodeGen.a lib/libLLVMGlobalISel.a lib/libLLVMAArch64AsmParser.a lib/libLLVMAArch64Disassembler.a lib/libLLVMAArch64Desc.a lib/libLLVMAArch64AsmPrinter.a lib/libLLVMAArch64Info.a lib/libLLVMAArch64Utils.a lib/libLLVMAMDGPUCodeGen.a lib/libLLVMAMDGPUAsmParser.a lib/libLLVMAMDGPUDisassembler.a lib/libLLVMAMDGPUDesc.a lib/libLLVMAMDGPUAsmPrinter.a lib/libLLVMAMDGPUInfo.a lib/libLLVMAMDGPUUtils.a lib/libLLVMARMCodeGen.a lib/libLLVMARMAsmParser.a lib/libLLVMARMDisassembler.a lib/libLLVMARMDesc.a lib/libLLVMARMAsmPrinter.a lib/libLLVMARMInfo.a lib/libLLVMBPFCodeGen.a lib/libLLVMBPFDesc.a lib/libLLVMBPFAsmPrinter.a lib/libLLVMBPFInfo.a lib/libLLVMHexagonCodeGen.a lib/libLLVMHexagonAsmParser.a lib/libLLVMHexagonDisassembler.a lib/libLLVMHexagonDesc.a lib/libLLVMHexagonInfo.a lib/libLLVMMipsCodeGen.a lib/libLLVMMipsAsmParser.a lib/libLLVMMipsDesc.a lib/libLLVMMipsAsmPrinter.a lib/libLLVMMipsDisassembler.a lib/libLLVMMipsInfo.a lib/libLLVMMSP430CodeGen.a lib/libLLVMMSP430Desc.a lib/libLLVMMSP430AsmPrinter.a lib/libLLVMMSP430Info.a lib/libLLVMNVPTXCodeGen.a lib/libLLVMNVPTXDesc.a lib/libLLVMNVPTXAsmPrinter.a lib/libLLVMNVPTXInfo.a lib/libLLVMPowerPCCodeGen.a lib/libLLVMPowerPCAsmParser.a lib/libLLVMPowerPCDesc.a lib/libLLVMPowerPCAsmPrinter.a lib/libLLVMPowerPCDisassembler.a lib/libLLVMPowerPCInfo.a lib/libLLVMSparcCodeGen.a lib/libLLVMSparcAsmParser.a lib/libLLVMSparcDesc.a lib/libLLVMSparcAsmPrinter.a lib/libLLVMSparcDisassembler.a lib/libLLVMSparcInfo.a lib/libLLVMSystemZCodeGen.a lib/libLLVMSystemZAsmParser.a lib/libLLVMSystemZDisassembler.a lib/libLLVMSystemZDesc.a lib/libLLVMSystemZAsmPrinter.a lib/libLLVMSystemZInfo.a lib/libLLVMX86CodeGen.a lib/libLLVMX86AsmParser.a lib/libLLVMX86Desc.a lib/libLLVMX86AsmPrinter.a lib/libLLVMX86Utils.a lib/libLLVMX86Disassembler.a lib/libLLVMX86Info.a lib/libLLVMXCoreCodeGen.a lib/libLLVMAsmPrinter.a lib/libLLVMDebugInfoCodeView.a lib/libLLVMSelectionDAG.a lib/libLLVMXCoreDesc.a lib/libLLVMXCoreAsmPrinter.a lib/libLLVMXCoreDisassembler.a lib/libLLVMXCoreInfo.a lib/libLLVMMCDisassembler.a lib/libLLVMLTO.a lib/libLLVMObjCARCOpts.a lib/libLLVMPasses.a lib/libLLVMCodeGen.a lib/libLLVMTarget.a lib/libLLVMBitWriter.a lib/libLLVMipo.a lib/libLLVMObject.a lib/libLLVMMCParser.a lib/libLLVMLinker.a lib/libLLVMIRReader.a lib/libLLVMBitReader.a lib/libLLVMAsmParser.a lib/libLLVMScalarOpts.a lib/libLLVMVectorize.a lib/libLLVMInstCombine.a lib/libLLVMInstrumentation.a lib/libLLVMMC.a lib/libLLVMTransformUtils.a lib/libLLVMAnalysis.a lib/libLLVMProfileData.a lib/libLLVMCore.a lib/libLLVMSupport.a -lrt -ldl -lpthread -lz -lm -rpath "\$ORIGIN/../lib" -lstdc++ -lm -lgcc_s -lgcc -lc -lgcc_s -lgcc /usr/lib/gcc/x86_64-linux-gnu/5.3.1/crtend.o /usr/lib/gcc/x86_64-linux-gnu/5.3.1/../../../x86_64-linux-gnu/crtn.o

My relink time is still about 0.2-0.3 seconds then:

222.831375      task-clock (msec)         #    0.999 CPUs utilized          
         0      context-switches          #    0.000 K/sec                  
         0      cpu-migrations            #    0.000 K/sec                  
    35,448      page-faults               #    0.159 M/sec

So I see we do the benchmark differently. That I guess the reason of why I had no difference in results here: https://reviews.llvm.org/D21681#466406.

lld/trunk/ELF/Config.h

struct Configuration {
   bool DiscardLocals;
   bool DiscardNone;
   bool EhFrameHdr;
   bool EnableNewDtags;
   bool ExportDynamic;
   bool FatalWarnings;
   bool GcSections;
   bool GnuHash = false;
-  bool HasVersionScript = false;
   bool ICF;
   bool Mips64EL = false;
   bool NoGnuUnique;
   bool NoUndefinedVersion;
   bool Pic;
   bool Pie;
   bool PrintGcSections;
   bool Rela;

lld/trunk/ELF/Driver.cpp

void LinkerDriver::readConfigs(opt::InputArgList &Args) {
 
   if (auto *Arg = Args.getLastArg(OPT_dynamic_list))
     if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
       parseDynamicList(*Buffer);
 
   for (auto *Arg : Args.filtered(OPT_export_dynamic_symbol))
     Config->DynamicList.push_back(Arg->getValue());
 
-  if (auto *Arg = Args.getLastArg(OPT_version_script)) {
-    Config->HasVersionScript = true;
+  if (auto *Arg = Args.getLastArg(OPT_version_script))
     if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
       parseVersionScript(*Buffer);
-  }
 
   for (auto *Arg : Args.filtered(OPT_trace_symbol))
     Config->TraceSymbol.insert(Arg->getValue());
 }
 
 void LinkerDriver::createFiles(opt::InputArgList &Args) {
   for (auto *Arg : Args) {
     switch (Arg->getOption().getID()) {
for (std::unique_ptr<InputFile> &F : Files)
     Symtab.addFile(std::move(F));
   if (HasError)
     return; // There were duplicate symbols or incompatible files
 
   Symtab.scanUndefinedFlags();
   Symtab.scanShlibUndefined();
   Symtab.scanDynamicList();
   Symtab.scanVersionScript();
+  Symtab.scanSymbolVersions();
   Symtab.traceDefined();
 
   Symtab.addCombinedLtoObject();
   if (HasError)
     return;
 
   for (auto *Arg : Args.filtered(OPT_wrap))
     Symtab.wrap(Arg->getValue());

lld/trunk/ELF/SymbolTable.h

public:
   Symbol *addCommon(StringRef N, uint64_t Size, uint64_t Alignment,
                     uint8_t Binding, uint8_t StOther, uint8_t Type,
                     InputFile *File);
 
   void scanUndefinedFlags();
   void scanShlibUndefined();
   void scanDynamicList();
   void scanVersionScript();
+  void scanSymbolVersions();
   void traceDefined();
 
   SymbolBody *find(StringRef Name);
   void wrap(StringRef Name);
 
 private:
   std::vector<SymbolBody *> findAll(StringRef Pattern);
   std::pair<Symbol *, bool> insert(StringRef Name);

lld/trunk/ELF/SymbolTable.cpp

 static uint8_t getMinVisibility(uint8_t VA, uint8_t VB) {
   if (VA == STV_DEFAULT)
     return VB;
   if (VB == STV_DEFAULT)
     return VA;
   return std::min(VA, VB);
 }
 
-// A symbol version may be included in a symbol name as a suffix after '@'.
-// This function parses that part and returns a version ID number.
-static uint16_t getVersionId(Symbol *Sym, StringRef Name) {
-  size_t VersionBegin = Name.find('@');
-  if (VersionBegin == StringRef::npos)
-    return Config->DefaultSymbolVersion;
-
-  // If symbol name contains '@' or '@@' we can assign its version id right
-  // here. '@@' means the default version. It is usually the most recent one.
-  // VERSYM_HIDDEN flag should be set for all non-default versions.
-  StringRef Version = Name.drop_front(VersionBegin + 1);
-  bool Default = Version.startswith("@");
-  if (Default)
-    Version = Version.drop_front();
-
-  for (VersionDefinition &V : Config->VersionDefinitions)
-    if (V.Name == Version)
-      return Default ? V.Id : (V.Id | VERSYM_HIDDEN);
-
-
-  // If we are not building shared and version script
-  // is not specified, then it is not a error, it is
-  // in common not to use script for linking executables.
-  // In this case we just create new version.
-  if (!Config->Shared && !Config->HasVersionScript) {
-    size_t Id = defineSymbolVersion(Version);
-    return Default ? Id : (Id | VERSYM_HIDDEN);
-  }
-
-  error("symbol " + Name + " has undefined version " + Version);
-  return 0;
-}
-
 // Find an existing symbol or create and insert a new one.
 template <class ELFT>
 std::pair<Symbol *, bool> SymbolTable<ELFT>::insert(StringRef Name) {
   unsigned NumSyms = SymVector.size();
   auto P = Symtab.insert(std::make_pair(Name, NumSyms));
   Symbol *Sym;
   if (P.second) {
     Sym = new (Alloc) Symbol;
     Sym->Binding = STB_WEAK;
     Sym->Visibility = STV_DEFAULT;
     Sym->IsUsedInRegularObj = false;
     Sym->ExportDynamic = false;
-    Sym->VersionId = getVersionId(Sym, Name);
-    Sym->VersionedName =
-        Sym->VersionId != VER_NDX_LOCAL && Sym->VersionId != VER_NDX_GLOBAL;
+    Sym->VersionId = Config->DefaultSymbolVersion;
     SymVector.push_back(Sym);
   } else {
     Sym = SymVector[P.first->second];
   }
   return {Sym, P.second};
 }
 
 // Find an existing symbol or create and insert a new one, then apply the given
for (size_t I = Config->VersionDefinitions.size() - 1; I != (size_t)-1; --I) {
     for (SymbolVersion &Sym : V.Globals)
       if (hasWildcard(Sym.Name))
         for (SymbolBody *B : findAll(Sym.Name))
           if (B->symbol()->VersionId == Config->DefaultSymbolVersion)
             B->symbol()->VersionId = V.Id;
   }
 }
 
+// Returns the size of the longest version name.
+static int getMaxVersionLen() {
+  size_t Len = 0;
+  for (VersionDefinition &V : Config->VersionDefinitions)
+    Len = std::max(Len, V.Name.size());
+  return Len;
+}
+
+// Parses a symbol name in the form of <name>@<version> or <name>@@<version>.
+static std::pair<StringRef, uint16_t>
+getSymbolVersion(SymbolBody *B, int MaxVersionLen) {
+  StringRef S = B->getName();
+
+  // MaxVersionLen was passed so that we don't need to scan
+  // all characters in a symbol name. It is effective because
+  // versions are usually short and symbol names can be very long.
+  size_t Pos = S.find('@', std::max(0, int(S.size()) - MaxVersionLen - 2));
+  if (Pos == 0 || Pos == StringRef::npos)
+    return {"", 0};
+
+  StringRef Name = S.substr(0, Pos);
+  StringRef Verstr = S.substr(Pos + 1);
+  if (Verstr.empty())
+    return {"", 0};
+
+  // '@@' in a symbol name means the default version.
+  // It is usually the most recent one.
+  bool IsDefault = (Verstr[0] == '@');
+  if (IsDefault)
+    Verstr = Verstr.substr(1);
+
+  for (VersionDefinition &V : Config->VersionDefinitions) {
+    if (V.Name == Verstr)
+      return {Name, IsDefault ? V.Id : (V.Id | VERSYM_HIDDEN)};
+  }
+
+  // It is an error if the specified version was not defined.
+  error("symbol " + S + " has undefined version " + Verstr);
+  return {"", 0};
+}
+
+// Versions are usually assigned to symbols using version scripts,
+// but there's another way to assign versions to symbols.
+// If a symbol name contains '@', the string after it is not
+// actually a part of the symbol name but specifies a version.
+// This function takes care of it.
+template <class ELFT> void SymbolTable<ELFT>::scanSymbolVersions() {
+  if (Config->VersionDefinitions.empty())
+    return;
+
+  int MaxVersionLen = getMaxVersionLen();
+
+  // Unfortunately there's no way other than iterating over all
+  // symbols to look for '@' characters in symbol names.
+  // So this is inherently slow. A good news is that we do this
+  // only when versions have been defined.
+  for (Symbol *Sym : SymVector) {
+    // Symbol versions for exported symbols are by nature
+    // only for defined global symbols.
+    SymbolBody *B = Sym->body();
+    if (!B->isDefined())
+      continue;
+    uint8_t Visibility = B->getVisibility();
+    if (Visibility != STV_DEFAULT && Visibility != STV_PROTECTED)
+      continue;
+
+    // Look for '@' in the symbol name.
+    StringRef Name;
+    uint16_t Version;
+    std::tie(Name, Version) = getSymbolVersion(B, MaxVersionLen);
+    if (Name.empty())
+      continue;
+
+    B->setName(Name);
+    Sym->VersionId = Version;
+  }
+}
+
 // Print the module names which define the notified
 // symbols provided through -y or --trace-symbol option.
 template <class ELFT> void SymbolTable<ELFT>::traceDefined() {
   for (const auto &Symbol : Config->TraceSymbol)
     if (SymbolBody *B = find(Symbol.getKey()))
       if (B->isDefined() || B->isCommon())
         if (B->File)
           outs() << getFilename(B->File) << ": definition of " << B->getName()
                  << "\n";
 }
 
 template class elf::SymbolTable<ELF32LE>;
 template class elf::SymbolTable<ELF32BE>;
 template class elf::SymbolTable<ELF64LE>;
 template class elf::SymbolTable<ELF64BE>;

lld/trunk/ELF/Symbols.h

public:
   bool isCommon() const { return SymbolKind == DefinedCommonKind; }
   bool isLazy() const {
     return SymbolKind == LazyArchiveKind || SymbolKind == LazyObjectKind;
   }
   bool isShared() const { return SymbolKind == SharedKind; }
   bool isLocal() const { return IsLocal; }
   bool isPreemptible() const;
 
-  // Returns the symbol name.
   StringRef getName() const;
+  void setName(StringRef S);
+
   uint32_t getNameOffset() const {
     assert(isLocal());
     return NameOffset;
   }
 
   uint8_t getVisibility() const { return StOther & 0x3; }
 
   unsigned DynsymIndex = 0;
struct Symbol {
   unsigned IsUsedInRegularObj : 1;
 
   // If this flag is true and the symbol has protected or default visibility, it
   // will appear in .dynsym. This flag is set by interposable DSO symbols in
   // executables, by most symbols in DSOs and executables built with
   // --export-dynamic, and by dynamic lists.
   unsigned ExportDynamic : 1;
 
-  // If this flag is true then symbol name also contains version name. Such
-  // name can have single or double symbol @. Double means that version is
-  // used as default. Single signals about depricated symbol version.
-  unsigned VersionedName : 1;
-
   bool includeInDynsym() const;
   bool isWeak() const { return Binding == llvm::ELF::STB_WEAK; }
 
   // This field is used to store the Symbol's SymbolBody. This instantiation of
   // AlignedCharArrayUnion gives us a struct with a char array field that is
   // large and aligned enough to store any derived class of SymbolBody. We
   // assume that the size and alignment of ELF64LE symbols is sufficient for any
   // ELFT, and we verify this with the static_asserts in replaceBody.

lld/trunk/ELF/Symbols.cpp

 
 SymbolBody::SymbolBody(Kind K, StringRef Name, uint8_t StOther, uint8_t Type)
     : SymbolKind(K), NeedsCopyOrPltAddr(false), IsLocal(false),
       IsInGlobalMipsGot(false), Type(Type), StOther(StOther),
       Name({Name.data(), Name.size()}) {}
 
 StringRef SymbolBody::getName() const {
   assert(!isLocal());
-  StringRef S = StringRef(Name.S, Name.Len);
-  if (!symbol()->VersionedName)
-    return S;
-  return S.substr(0, S.find('@'));
+  return StringRef(Name.S, Name.Len);
+}
+
+void SymbolBody::setName(StringRef S) {
+  Name.S = S.data();
+  Name.Len = S.size();
 }
 
 // Returns true if a symbol can be replaced at load-time by a symbol
 // with the same name defined in other ELF executable or DSO.
 bool SymbolBody::isPreemptible() const {
   if (isLocal())
     return false;
 

lld/trunk/test/ELF/verdef-defaultver.s

 # EXE-NEXT:        Hash: 98456416
 # EXE-NEXT:        Flags: 0x0
 # EXE-NEXT:        Index: 3
 # EXE-NEXT:        Name: LIBSAMPLE_2.0
 # EXE-NEXT:      }
 # EXE-NEXT:    }
 # EXE-NEXT:  }
 
-# RUN: not ld.lld -shared %t1 -o %terr.so 2>&1 | \
-# RUN:   FileCheck -check-prefix=ERR1 %s
-# ERR1: symbol b@@LIBSAMPLE_2.0 has undefined version LIBSAMPLE_2.0
-
 .globl _start
 _start:
   callq a
   callq b
   callq c

lld/trunk/test/ELF/verdef-executable.s

-# REQUIRES: x86
-
-# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t1
-# RUN: ld.lld %t1 -o %t
-# RUN: llvm-readobj -t -V -dyn-symbols %t | FileCheck --check-prefix=EXE %s
-
-# EXE:      Symbols [
-# EXE-NEXT:    Symbol {
-# EXE-NEXT:      Name:
-# EXE-NEXT:      Value: 0x0
-# EXE-NEXT:      Size: 0
-# EXE-NEXT:      Binding: Local
-# EXE-NEXT:      Type: None (0x0)
-# EXE-NEXT:      Other: 0
-# EXE-NEXT:      Section: Undefined (0x0)
-# EXE-NEXT:    }
-# EXE-NEXT:    Symbol {
-# EXE-NEXT:      Name: _start
-# EXE-NEXT:      Value: 0x11004
-# EXE-NEXT:      Size: 0
-# EXE-NEXT:      Binding: Global
-# EXE-NEXT:      Type: None
-# EXE-NEXT:      Other: 0
-# EXE-NEXT:      Section: .text
-# EXE-NEXT:    }
-# EXE-NEXT:    Symbol {
-# EXE-NEXT:      Name: a
-# EXE-NEXT:      Value: 0x11000
-# EXE-NEXT:      Size: 0
-# EXE-NEXT:      Binding: Global
-# EXE-NEXT:      Type: Function
-# EXE-NEXT:      Other: 0
-# EXE-NEXT:      Section: .text
-# EXE-NEXT:    }
-# EXE-NEXT:    Symbol {
-# EXE-NEXT:      Name: b
-# EXE-NEXT:      Value: 0x11002
-# EXE-NEXT:      Size: 0
-# EXE-NEXT:      Binding: Global
-# EXE-NEXT:      Type: Function
-# EXE-NEXT:      Other: 0
-# EXE-NEXT:      Section: .text
-# EXE-NEXT:    }
-# EXE-NEXT:    Symbol {
-# EXE-NEXT:      Name: b
-# EXE-NEXT:      Value: 0x11001
-# EXE-NEXT:      Size: 0
-# EXE-NEXT:      Binding: Global
-# EXE-NEXT:      Type: Function
-# EXE-NEXT:      Other: 0
-# EXE-NEXT:      Section: .text
-# EXE-NEXT:    }
-# EXE-NEXT:    Symbol {
-# EXE-NEXT:      Name: b_1
-# EXE-NEXT:      Value: 0x11001
-# EXE-NEXT:      Size: 0
-# EXE-NEXT:      Binding: Global
-# EXE-NEXT:      Type: Function
-# EXE-NEXT:      Other: 0
-# EXE-NEXT:      Section: .text
-# EXE-NEXT:    }
-# EXE-NEXT:    Symbol {
-# EXE-NEXT:      Name: b_2
-# EXE-NEXT:      Value: 0x11002
-# EXE-NEXT:      Size: 0
-# EXE-NEXT:      Binding: Global
-# EXE-NEXT:      Type: Function
-# EXE-NEXT:      Other: 0
-# EXE-NEXT:      Section: .text
-# EXE-NEXT:    }
-# EXE-NEXT:    Symbol {
-# EXE-NEXT:      Name: c
-# EXE-NEXT:      Value: 0x11003
-# EXE-NEXT:      Size: 0
-# EXE-NEXT:      Binding: Global
-# EXE-NEXT:      Type: Function
-# EXE-NEXT:      Other: 0
-# EXE-NEXT:      Section: .text
-# EXE-NEXT:    }
-# EXE-NEXT:  ]
-# EXE-NEXT: DynamicSymbols [
-# EXE-NEXT: ]
-# EXE-NEXT: Version symbols {
-# EXE-NEXT: }
-# EXE-NEXT: SHT_GNU_verdef {
-# EXE-NEXT: }
-# EXE-NEXT: SHT_GNU_verneed {
-# EXE-NEXT: }
-
-# RUN: ld.lld -pie --export-dynamic %t1 -o %t2
-# RUN: llvm-readobj -t -V -dyn-symbols %t2 | \
-# RUN:   FileCheck --check-prefix=EXEDYN %s
-
-# EXEDYN:      DynamicSymbols [
-# EXEDYN-NEXT:    Symbol {
-# EXEDYN-NEXT:      Name: @
-# EXEDYN-NEXT:      Value: 0x0
-# EXEDYN-NEXT:      Size: 0
-# EXEDYN-NEXT:      Binding: Local
-# EXEDYN-NEXT:      Type: None
-# EXEDYN-NEXT:      Other: 0
-# EXEDYN-NEXT:      Section: Undefined
-# EXEDYN-NEXT:    }
-# EXEDYN-NEXT:    Symbol {
-# EXEDYN-NEXT:      Name: _start@
-# EXEDYN-NEXT:      Value: 0x1004
-# EXEDYN-NEXT:      Size: 0
-# EXEDYN-NEXT:      Binding: Global
-# EXEDYN-NEXT:      Type: None
-# EXEDYN-NEXT:      Other: 0
-# EXEDYN-NEXT:      Section: .text
-# EXEDYN-NEXT:    }
-# EXEDYN-NEXT:    Symbol {
-# EXEDYN-NEXT:      Name: a@
-# EXEDYN-NEXT:      Value: 0x1000
-# EXEDYN-NEXT:      Size: 0
-# EXEDYN-NEXT:      Binding: Global
-# EXEDYN-NEXT:      Type: Function
-# EXEDYN-NEXT:      Other: 0
-# EXEDYN-NEXT:      Section: .text
-# EXEDYN-NEXT:    }
-# EXEDYN-NEXT:    Symbol {
-# EXEDYN-NEXT:      Name: b@@LIBSAMPLE_2.0
-# EXEDYN-NEXT:      Value: 0x1002
-# EXEDYN-NEXT:      Size: 0
-# EXEDYN-NEXT:      Binding: Global
-# EXEDYN-NEXT:      Type: Function
-# EXEDYN-NEXT:      Other: 0
-# EXEDYN-NEXT:      Section: .text
-# EXEDYN-NEXT:    }
-# EXEDYN-NEXT:    Symbol {
-# EXEDYN-NEXT:      Name: b@LIBSAMPLE_1.0
-# EXEDYN-NEXT:      Value: 0x1001
-# EXEDYN-NEXT:      Size: 0
-# EXEDYN-NEXT:      Binding: Global
-# EXEDYN-NEXT:      Type: Function
-# EXEDYN-NEXT:      Other: 0
-# EXEDYN-NEXT:      Section: .text
-# EXEDYN-NEXT:    }
-# EXEDYN-NEXT:    Symbol {
-# EXEDYN-NEXT:      Name: b_1@
-# EXEDYN-NEXT:      Value: 0x1001
-# EXEDYN-NEXT:      Size: 0
-# EXEDYN-NEXT:      Binding: Global
-# EXEDYN-NEXT:      Type: Function
-# EXEDYN-NEXT:      Other: 0
-# EXEDYN-NEXT:      Section: .text
-# EXEDYN-NEXT:    }
-# EXEDYN-NEXT:    Symbol {
-# EXEDYN-NEXT:      Name: b_2@
-# EXEDYN-NEXT:      Value: 0x1002
-# EXEDYN-NEXT:      Size: 0
-# EXEDYN-NEXT:      Binding: Global
-# EXEDYN-NEXT:      Type: Function
-# EXEDYN-NEXT:      Other: 0
-# EXEDYN-NEXT:      Section: .text
-# EXEDYN-NEXT:    }
-# EXEDYN-NEXT:    Symbol {
-# EXEDYN-NEXT:      Name: c@
-# EXEDYN-NEXT:      Value: 0x1003
-# EXEDYN-NEXT:      Size: 0
-# EXEDYN-NEXT:      Binding: Global
-# EXEDYN-NEXT:      Type: Function
-# EXEDYN-NEXT:      Other: 0
-# EXEDYN-NEXT:      Section: .text
-# EXEDYN-NEXT:    }
-# EXEDYN-NEXT:  ]
-# EXEDYN-NEXT:  Version symbols {
-# EXEDYN-NEXT:    Section Name: .gnu.version
-# EXEDYN-NEXT:    Address: 0x288
-# EXEDYN-NEXT:    Offset: 0x288
-# EXEDYN-NEXT:    Link: 1
-# EXEDYN-NEXT:    Symbols [
-# EXEDYN-NEXT:      Symbol {
-# EXEDYN-NEXT:        Version: 0
-# EXEDYN-NEXT:        Name: @
-# EXEDYN-NEXT:      }
-# EXEDYN-NEXT:      Symbol {
-# EXEDYN-NEXT:        Version: 1
-# EXEDYN-NEXT:        Name: _start@
-# EXEDYN-NEXT:      }
-# EXEDYN-NEXT:      Symbol {
-# EXEDYN-NEXT:        Version: 1
-# EXEDYN-NEXT:        Name: a@
-# EXEDYN-NEXT:      }
-# EXEDYN-NEXT:      Symbol {
-# EXEDYN-NEXT:        Version: 2
-# EXEDYN-NEXT:        Name: b@@LIBSAMPLE_2.0
-# EXEDYN-NEXT:      }
-# EXEDYN-NEXT:      Symbol {
-# EXEDYN-NEXT:        Version: 3
-# EXEDYN-NEXT:        Name: b@LIBSAMPLE_1.0
-# EXEDYN-NEXT:      }
-# EXEDYN-NEXT:      Symbol {
-# EXEDYN-NEXT:        Version: 1
-# EXEDYN-NEXT:        Name: b_1@
-# EXEDYN-NEXT:      }
-# EXEDYN-NEXT:      Symbol {
-# EXEDYN-NEXT:        Version: 1
-# EXEDYN-NEXT:        Name: b_2@
-# EXEDYN-NEXT:      }
-# EXEDYN-NEXT:      Symbol {
-# EXEDYN-NEXT:        Version: 1
-# EXEDYN-NEXT:        Name: c@
-# EXEDYN-NEXT:      }
-# EXEDYN-NEXT:    ]
-# EXEDYN-NEXT:  }
-# EXEDYN-NEXT:  SHT_GNU_verdef {
-# EXEDYN-NEXT:    Definition {
-# EXEDYN-NEXT:      Version: 1
-# EXEDYN-NEXT:      Flags: Base
-# EXEDYN-NEXT:      Index: 1
-# EXEDYN-NEXT:      Hash:
-# EXEDYN-NEXT:      Name:
-# EXEDYN-NEXT:    }
-# EXEDYN-NEXT:    Definition {
-# EXEDYN-NEXT:      Version: 1
-# EXEDYN-NEXT:      Flags: 0x0
-# EXEDYN-NEXT:      Index: 2
-# EXEDYN-NEXT:      Hash: 98456416
-# EXEDYN-NEXT:      Name: LIBSAMPLE_2.0
-# EXEDYN-NEXT:    }
-# EXEDYN-NEXT:    Definition {
-# EXEDYN-NEXT:      Version: 1
-# EXEDYN-NEXT:      Flags: 0x0
-# EXEDYN-NEXT:      Index: 3
-# EXEDYN-NEXT:      Hash: 98457184
-# EXEDYN-NEXT:      Name: LIBSAMPLE_1.0
-# EXEDYN-NEXT:    }
-# EXEDYN-NEXT:  }
-# EXEDYN-NEXT:  SHT_GNU_verneed {
-# EXEDYN-NEXT:  }
-
-## Check when linking executable that error produced if version script
-## was specified and there are symbols with version in name that
-## is absent in script.
-# RUN: echo    "VERSION { \
-# RUN:          global: foo;   \
-# RUN:          local: *; }; " > %t.script
-# RUN: not ld.lld --version-script %t.script %t1 -o %t3 2>&1 | \
-# RUN:   FileCheck -check-prefix=ERR %s
-# ERR: symbol b@LIBSAMPLE_1.0 has undefined version LIBSAMPLE_1.0
-
-b@LIBSAMPLE_1.0 = b_1
-b@@LIBSAMPLE_2.0 = b_2
-
-.globl a
-.type  a,@function
-a:
-retq
-
-.globl b_1
-.type  b_1,@function
-b_1:
-retq
-
-.globl b_2
-.type  b_2,@function
-b_2:
-retq
-
-.globl c
-.type  c,@function
-c:
-retq
-
-.globl _start
-_start:
- nop