Introduce new linkage types linkonce_odr, weak_odr, common_odr

and extern_weak_odr.  These are the same as the non-odr versions,
except that they indicate that the global will only be overridden
by an *equivalent* global.  In C, a function with weak linkage can
be overridden by a function which behaves completely differently.
This means that IP passes have to skip weak functions, since any
deductions made from the function definition might be wrong, since
the definition could be replaced by something completely different
at link time.   This is not allowed in C++, thanks to the ODR
(One-Definition-Rule): if a function is replaced by another at
link-time, then the new function must be the same as the original
function.  If a language knows that a function or other global can
only be overridden by an equivalent global, it can give it the
weak_odr linkage type, and the optimizers will understand that it
is alright to make deductions based on the function body.  The
code generators on the other hand map weak and weak_odr linkage
to the same thing.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@66339 91177308-0d34-0410-b5e6-96231b3b80d8

36 files changed, 259 insertions, 155 deletions

diff --git a/lib/Analysis/DebugInfo.cpp b/lib/Analysis/DebugInfo.cpp
index deb5c9b..a063aa5 100644
--- a/lib/Analysis/DebugInfo.cpp
+++ b/lib/Analysis/DebugInfo.cpp
@@ -344,7 +344,7 @@ DIAnchor DIFactory::GetOrCreateAnchor(unsigned TAG, const char *Name) {
   if (GV->hasInitializer()) 
     return SubProgramAnchor = DIAnchor(GV);
   
-  GV->setLinkage(GlobalValue::LinkOnceLinkage);
+  GV->setLinkage(GlobalValue::LinkOnceAnyLinkage);
   GV->setSection("llvm.metadata");
   GV->setConstant(true);
   M.addTypeName("llvm.dbg.anchor.type", EltTy);
diff --git a/lib/AsmParser/LLLexer.cpp b/lib/AsmParser/LLLexer.cpp
index fb491d3..6f1d5ee 100644
--- a/lib/AsmParser/LLLexer.cpp
+++ b/lib/AsmParser/LLLexer.cpp
@@ -456,15 +456,19 @@ lltok::Kind LLLexer::LexIdentifier() {
   KEYWORD(private);
   KEYWORD(internal);
   KEYWORD(linkonce);
+  KEYWORD(linkonce_odr);
   KEYWORD(weak);
+  KEYWORD(weak_odr);
   KEYWORD(appending);
   KEYWORD(dllimport);
   KEYWORD(dllexport);
   KEYWORD(common);
+  KEYWORD(common_odr);
   KEYWORD(default);
   KEYWORD(hidden);
   KEYWORD(protected);
   KEYWORD(extern_weak);
+  KEYWORD(extern_weak_odr);
   KEYWORD(external);
   KEYWORD(thread_local);
   KEYWORD(zeroinitializer);
diff --git a/lib/AsmParser/LLParser.cpp b/lib/AsmParser/LLParser.cpp
index 19f8415..90dd507 100644
--- a/lib/AsmParser/LLParser.cpp
+++ b/lib/AsmParser/LLParser.cpp
@@ -116,12 +116,16 @@ bool LLParser::ParseTopLevelEntities() {
     case lltok::kw_private:       // OptionalLinkage
     case lltok::kw_internal:      // OptionalLinkage
     case lltok::kw_weak:          // OptionalLinkage
+    case lltok::kw_weak_odr:      // OptionalLinkage
     case lltok::kw_linkonce:      // OptionalLinkage
+    case lltok::kw_linkonce_odr:  // OptionalLinkage
     case lltok::kw_appending:     // OptionalLinkage
     case lltok::kw_dllexport:     // OptionalLinkage
     case lltok::kw_common:        // OptionalLinkage
+    case lltok::kw_common_odr:    // OptionalLinkage
     case lltok::kw_dllimport:     // OptionalLinkage
     case lltok::kw_extern_weak:   // OptionalLinkage
+    case lltok::kw_extern_weak_odr: // OptionalLinkage
     case lltok::kw_external: {    // OptionalLinkage
       unsigned Linkage, Visibility;
       if (ParseOptionalLinkage(Linkage) ||
@@ -377,7 +381,8 @@ bool LLParser::ParseAlias(const std::string &Name, LocTy NameLoc,
     return true;
 
   if (Linkage != GlobalValue::ExternalLinkage &&
-      Linkage != GlobalValue::WeakLinkage &&
+      Linkage != GlobalValue::WeakAnyLinkage &&
+      Linkage != GlobalValue::WeakODRLinkage &&
       Linkage != GlobalValue::InternalLinkage &&
       Linkage != GlobalValue::PrivateLinkage)
     return Error(LinkageLoc, "invalid linkage type for alias");
@@ -461,7 +466,8 @@ bool LLParser::ParseGlobal(const std::string &Name, LocTy NameLoc,
   // present.
   Constant *Init = 0;
   if (!HasLinkage || (Linkage != GlobalValue::DLLImportLinkage &&
-                      Linkage != GlobalValue::ExternalWeakLinkage &&
+                      Linkage != GlobalValue::ExternalWeakAnyLinkage &&
+                      Linkage != GlobalValue::ExternalWeakODRLinkage &&
                       Linkage != GlobalValue::ExternalLinkage)) {
     if (ParseGlobalValue(Ty, Init))
       return true;
@@ -576,10 +582,10 @@ GlobalValue *LLParser::GetGlobalVal(const std::string &Name, const Type *Ty,
       return 0;
     }
     
-    FwdVal = Function::Create(FT, GlobalValue::ExternalWeakLinkage, Name, M);
+    FwdVal = Function::Create(FT, GlobalValue::ExternalWeakAnyLinkage, Name, M);
   } else {
     FwdVal = new GlobalVariable(PTy->getElementType(), false,
-                                GlobalValue::ExternalWeakLinkage, 0, Name, M);
+                                GlobalValue::ExternalWeakAnyLinkage, 0, Name, M);
   }
   
   ForwardRefVals[Name] = std::make_pair(FwdVal, Loc);
@@ -620,10 +626,10 @@ GlobalValue *LLParser::GetGlobalVal(unsigned ID, const Type *Ty, LocTy Loc) {
       Error(Loc, "function may not return opaque type");
       return 0;
     }
-    FwdVal = Function::Create(FT, GlobalValue::ExternalWeakLinkage, "", M);
+    FwdVal = Function::Create(FT, GlobalValue::ExternalWeakAnyLinkage, "", M);
   } else {
     FwdVal = new GlobalVariable(PTy->getElementType(), false,
-                                GlobalValue::ExternalWeakLinkage, 0, "", M);
+                                GlobalValue::ExternalWeakAnyLinkage, 0, "", M);
   }
   
   ForwardRefValIDs[ID] = std::make_pair(FwdVal, Loc);
@@ -746,27 +752,36 @@ bool LLParser::ParseOptionalAttrs(unsigned &Attrs, unsigned AttrKind) {
 ///   ::= 'private'
 ///   ::= 'internal'
 ///   ::= 'weak'
+///   ::= 'weak_odr'
 ///   ::= 'linkonce'
+///   ::= 'linkonce_odr'
 ///   ::= 'appending'
 ///   ::= 'dllexport'
 ///   ::= 'common'
+///   ::= 'common_odr'
 ///   ::= 'dllimport'
 ///   ::= 'extern_weak'
+///   ::= 'extern_weak_odr'
 ///   ::= 'external'
 bool LLParser::ParseOptionalLinkage(unsigned &Res, bool &HasLinkage) {
   HasLinkage = false;
   switch (Lex.getKind()) {
-  default:                    Res = GlobalValue::ExternalLinkage; return false;
-  case lltok::kw_private:     Res = GlobalValue::PrivateLinkage; break;
-  case lltok::kw_internal:    Res = GlobalValue::InternalLinkage; break;
-  case lltok::kw_weak:        Res = GlobalValue::WeakLinkage; break;
-  case lltok::kw_linkonce:    Res = GlobalValue::LinkOnceLinkage; break;
-  case lltok::kw_appending:   Res = GlobalValue::AppendingLinkage; break;
-  case lltok::kw_dllexport:   Res = GlobalValue::DLLExportLinkage; break;
-  case lltok::kw_common:      Res = GlobalValue::CommonLinkage; break;
-  case lltok::kw_dllimport:   Res = GlobalValue::DLLImportLinkage; break;
-  case lltok::kw_extern_weak: Res = GlobalValue::ExternalWeakLinkage; break;
-  case lltok::kw_external:    Res = GlobalValue::ExternalLinkage; break;
+  default:                     Res = GlobalValue::ExternalLinkage; return false;
+  case lltok::kw_private:      Res = GlobalValue::PrivateLinkage; break;
+  case lltok::kw_internal:     Res = GlobalValue::InternalLinkage; break;
+  case lltok::kw_weak:         Res = GlobalValue::WeakAnyLinkage; break;
+  case lltok::kw_weak_odr:     Res = GlobalValue::WeakODRLinkage; break;
+  case lltok::kw_linkonce:     Res = GlobalValue::LinkOnceAnyLinkage; break;
+  case lltok::kw_linkonce_odr: Res = GlobalValue::LinkOnceODRLinkage; break;
+  case lltok::kw_appending:    Res = GlobalValue::AppendingLinkage; break;
+  case lltok::kw_dllexport:    Res = GlobalValue::DLLExportLinkage; break;
+  case lltok::kw_common:       Res = GlobalValue::CommonAnyLinkage; break;
+  case lltok::kw_common_odr:   Res = GlobalValue::CommonODRLinkage; break;
+  case lltok::kw_dllimport:    Res = GlobalValue::DLLImportLinkage; break;
+  case lltok::kw_extern_weak:  Res = GlobalValue::ExternalWeakAnyLinkage; break;
+  case lltok::kw_extern_weak_odr:
+                               Res = GlobalValue::ExternalWeakODRLinkage; break;
+  case lltok::kw_external:     Res = GlobalValue::ExternalLinkage; break;
   }
   Lex.Lex();
   HasLinkage = true;
@@ -2074,21 +2089,25 @@ bool LLParser::ParseFunctionHeader(Function *&Fn, bool isDefine) {
   case GlobalValue::ExternalLinkage:
     break; // always ok.
   case GlobalValue::DLLImportLinkage:
-  case GlobalValue::ExternalWeakLinkage:
+  case GlobalValue::ExternalWeakAnyLinkage:
+  case GlobalValue::ExternalWeakODRLinkage:
     if (isDefine)
       return Error(LinkageLoc, "invalid linkage for function definition");
     break;
   case GlobalValue::PrivateLinkage:
   case GlobalValue::InternalLinkage:
-  case GlobalValue::LinkOnceLinkage:
-  case GlobalValue::WeakLinkage:
+  case GlobalValue::LinkOnceAnyLinkage:
+  case GlobalValue::LinkOnceODRLinkage:
+  case GlobalValue::WeakAnyLinkage:
+  case GlobalValue::WeakODRLinkage:
   case GlobalValue::DLLExportLinkage:
     if (!isDefine)
       return Error(LinkageLoc, "invalid linkage for function declaration");
     break;
   case GlobalValue::AppendingLinkage:
   case GlobalValue::GhostLinkage:
-  case GlobalValue::CommonLinkage:
+  case GlobalValue::CommonAnyLinkage:
+  case GlobalValue::CommonODRLinkage:
     return Error(LinkageLoc, "invalid function linkage type");
   }
   
diff --git a/lib/AsmParser/LLToken.h b/lib/AsmParser/LLToken.h
index e3bc908..efdc77a 100644
--- a/lib/AsmParser/LLToken.h
+++ b/lib/AsmParser/LLToken.h
@@ -36,9 +36,10 @@ namespace lltok {
     kw_declare, kw_define,
     kw_global,  kw_constant,
 
-    kw_private, kw_internal, kw_linkonce, kw_weak, kw_appending, kw_dllimport,
-    kw_dllexport, kw_common, kw_default, kw_hidden, kw_protected,
-    kw_extern_weak,
+    kw_private, kw_internal, kw_linkonce, kw_linkonce_odr, kw_weak, kw_weak_odr,
+    kw_appending, kw_dllimport, kw_dllexport, kw_common, kw_common_odr,
+    kw_default, kw_hidden, kw_protected,
+    kw_extern_weak, kw_extern_weak_odr,
     kw_external, kw_thread_local,
     kw_zeroinitializer,
     kw_undef, kw_null,
diff --git a/lib/Bitcode/Reader/BitcodeReader.cpp b/lib/Bitcode/Reader/BitcodeReader.cpp
index 2ddfbe3..0fe6fc6 100644
--- a/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -59,15 +59,19 @@ static GlobalValue::LinkageTypes GetDecodedLinkage(unsigned Val) {
   switch (Val) {
   default: // Map unknown/new linkages to external
   case 0: return GlobalValue::ExternalLinkage;
-  case 1: return GlobalValue::WeakLinkage;
+  case 1: return GlobalValue::WeakAnyLinkage;
   case 2: return GlobalValue::AppendingLinkage;
   case 3: return GlobalValue::InternalLinkage;
-  case 4: return GlobalValue::LinkOnceLinkage;
+  case 4: return GlobalValue::LinkOnceAnyLinkage;
   case 5: return GlobalValue::DLLImportLinkage;
   case 6: return GlobalValue::DLLExportLinkage;
-  case 7: return GlobalValue::ExternalWeakLinkage;
-  case 8: return GlobalValue::CommonLinkage;
+  case 7: return GlobalValue::ExternalWeakAnyLinkage;
+  case 8: return GlobalValue::CommonAnyLinkage;
   case 9: return GlobalValue::PrivateLinkage;
+  case 10: return GlobalValue::WeakODRLinkage;
+  case 11: return GlobalValue::LinkOnceODRLinkage;
+  case 12: return GlobalValue::ExternalWeakODRLinkage;
+  case 13: return GlobalValue::CommonODRLinkage;
   }
 }
 
diff --git a/lib/Bitcode/Writer/BitcodeWriter.cpp b/lib/Bitcode/Writer/BitcodeWriter.cpp
index 5633f0f..fefffbe 100644
--- a/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -276,15 +276,19 @@ static unsigned getEncodedLinkage(const GlobalValue *GV) {
   default: assert(0 && "Invalid linkage!");
   case GlobalValue::GhostLinkage:  // Map ghost linkage onto external.
   case GlobalValue::ExternalLinkage:     return 0;
-  case GlobalValue::WeakLinkage:         return 1;
+  case GlobalValue::WeakAnyLinkage:      return 1;
   case GlobalValue::AppendingLinkage:    return 2;
   case GlobalValue::InternalLinkage:     return 3;
-  case GlobalValue::LinkOnceLinkage:     return 4;
+  case GlobalValue::LinkOnceAnyLinkage:  return 4;
   case GlobalValue::DLLImportLinkage:    return 5;
   case GlobalValue::DLLExportLinkage:    return 6;
-  case GlobalValue::ExternalWeakLinkage: return 7;
-  case GlobalValue::CommonLinkage:       return 8;
+  case GlobalValue::ExternalWeakAnyLinkage: return 7;
+  case GlobalValue::CommonAnyLinkage:    return 8;
   case GlobalValue::PrivateLinkage:      return 9;
+  case GlobalValue::WeakODRLinkage:      return 10;
+  case GlobalValue::LinkOnceODRLinkage:  return 11;
+  case GlobalValue::ExternalWeakODRLinkage: return 12;
+  case GlobalValue::CommonODRLinkage:    return 13;
   }
 }
 
diff --git a/lib/CodeGen/AsmPrinter/DwarfWriter.cpp b/lib/CodeGen/AsmPrinter/DwarfWriter.cpp
index 5c4957a..9181216 100644
--- a/lib/CodeGen/AsmPrinter/DwarfWriter.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfWriter.cpp
@@ -3135,9 +3135,8 @@ public:
     GlobalVariable *GV = getGlobalVariable(V);
     if (!GV)
       return false;
-    
-    if (GV->getLinkage() != GlobalValue::InternalLinkage
-        && GV->getLinkage() != GlobalValue::LinkOnceLinkage)
+
+    if (!GV->hasInternalLinkage () && !GV->hasLinkOnceLinkage())
       return false;
 
     DIDescriptor DI(GV);
@@ -3449,8 +3448,10 @@ class DwarfException : public Dwarf  {
     }
 
     // If corresponding function is weak definition, this should be too.
-    if ((linkage == Function::WeakLinkage ||
-         linkage == Function::LinkOnceLinkage) &&
+    if ((linkage == Function::WeakAnyLinkage ||
+         linkage == Function::WeakODRLinkage ||
+         linkage == Function::LinkOnceAnyLinkage ||
+         linkage == Function::LinkOnceODRLinkage) &&
         TAI->getWeakDefDirective())
       O << TAI->getWeakDefDirective() << EHFrameInfo.FnName << "\n";
 
@@ -3461,8 +3462,10 @@ class DwarfException : public Dwarf  {
     // unwind info is to be available for non-EH uses.
     if (!EHFrameInfo.hasCalls &&
         !UnwindTablesMandatory &&
-        ((linkage != Function::WeakLinkage &&
-          linkage != Function::LinkOnceLinkage) ||
+        ((linkage != Function::WeakAnyLinkage &&
+          linkage != Function::WeakODRLinkage &&
+          linkage != Function::LinkOnceAnyLinkage &&
+          linkage != Function::LinkOnceODRLinkage) ||
          !TAI->getWeakDefDirective() ||
          TAI->getSupportsWeakOmittedEHFrame()))
     {
diff --git a/lib/CodeGen/ELFWriter.cpp b/lib/CodeGen/ELFWriter.cpp
index 7cca74b..ddc4e35 100644
--- a/lib/CodeGen/ELFWriter.cpp
+++ b/lib/CodeGen/ELFWriter.cpp
@@ -174,8 +174,10 @@ bool ELFCodeEmitter::finishFunction(MachineFunction &F) {
   case GlobalValue::ExternalLinkage:
     FnSym.SetBind(ELFWriter::ELFSym::STB_GLOBAL);
     break;
-  case GlobalValue::LinkOnceLinkage:
-  case GlobalValue::WeakLinkage:
+  case GlobalValue::LinkOnceAnyLinkage:
+  case GlobalValue::LinkOnceODRLinkage:
+  case GlobalValue::WeakAnyLinkage:
+  case GlobalValue::WeakODRLinkage:
     FnSym.SetBind(ELFWriter::ELFSym::STB_WEAK);
     break;
   case GlobalValue::PrivateLinkage:
diff --git a/lib/CodeGen/IntrinsicLowering.cpp b/lib/CodeGen/IntrinsicLowering.cpp
index 5b4de27..56b1736 100644
--- a/lib/CodeGen/IntrinsicLowering.cpp
+++ b/lib/CodeGen/IntrinsicLowering.cpp
@@ -316,7 +316,7 @@ static Instruction *LowerPartSelect(CallInst *CI) {
       Name[i] = '_';
   Module* M = F->getParent();
   F = cast<Function>(M->getOrInsertFunction(Name, FT));
-  F->setLinkage(GlobalValue::WeakLinkage);
+  F->setLinkage(GlobalValue::WeakAnyLinkage);
 
   // If we haven't defined the impl function yet, do so now
   if (F->isDeclaration()) {
@@ -490,7 +490,7 @@ static Instruction *LowerPartSet(CallInst *CI) {
       Name[i] = '_';
   Module* M = F->getParent();
   F = cast<Function>(M->getOrInsertFunction(Name, FT));
-  F->setLinkage(GlobalValue::WeakLinkage);
+  F->setLinkage(GlobalValue::WeakAnyLinkage);
 
   // If we haven't defined the impl function yet, do so now
   if (F->isDeclaration()) {
diff --git a/lib/CodeGen/MachOWriter.cpp b/lib/CodeGen/MachOWriter.cpp
index 22c2157..5fe05a4 100644
--- a/lib/CodeGen/MachOWriter.cpp
+++ b/lib/CodeGen/MachOWriter.cpp
@@ -956,9 +956,12 @@ MachOSym::MachOSym(const GlobalValue *gv, std::string name, uint8_t sect,
   default:
     assert(0 && "Unexpected linkage type!");
     break;
-  case GlobalValue::WeakLinkage:
-  case GlobalValue::LinkOnceLinkage:
-  case GlobalValue::CommonLinkage:
+  case GlobalValue::WeakAnyLinkage:
+  case GlobalValue::WeakODRLinkage:
+  case GlobalValue::LinkOnceAnyLinkage:
+  case GlobalValue::LinkOnceODRLinkage:
+  case GlobalValue::CommonAnyLinkage:
+  case GlobalValue::CommonODRLinkage:
     assert(!isa<Function>(gv) && "Unexpected linkage type for Function!");
   case GlobalValue::ExternalLinkage:
     GVName = TAI->getGlobalPrefix() + name;
diff --git a/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 7913c01..a08dcb2 100644
--- a/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -728,7 +728,7 @@ TargetLowering::isOffsetFoldingLegal(const GlobalAddressSDNode *GA) const {
   if (getTargetMachine().getRelocationModel() == Reloc::DynamicNoPIC &&
       GA &&
       !GA->getGlobal()->isDeclaration() &&
-      !GA->getGlobal()->mayBeOverridden())
+      !GA->getGlobal()->isWeakForLinker())
     return true;
 
   // Otherwise assume nothing is safe.
diff --git a/lib/CodeGen/ShadowStackGC.cpp b/lib/CodeGen/ShadowStackGC.cpp
index 5a55760..2402f81 100644
--- a/lib/CodeGen/ShadowStackGC.cpp
+++ b/lib/CodeGen/ShadowStackGC.cpp
@@ -293,12 +293,12 @@ bool ShadowStackGC::initializeCustomLowering(Module &M) {
     // If the root chain does not exist, insert a new one with linkonce
     // linkage!
     Head = new GlobalVariable(StackEntryPtrTy, false,
-                              GlobalValue::LinkOnceLinkage,
+                              GlobalValue::LinkOnceAnyLinkage,
                               Constant::getNullValue(StackEntryPtrTy),
                               "llvm_gc_root_chain", &M);
   } else if (Head->hasExternalLinkage() && Head->isDeclaration()) {
     Head->setInitializer(Constant::getNullValue(StackEntryPtrTy));
-    Head->setLinkage(GlobalValue::LinkOnceLinkage);
+    Head->setLinkage(GlobalValue::LinkOnceAnyLinkage);
   }
 
   return true;
diff --git a/lib/ExecutionEngine/JIT/JIT.cpp b/lib/ExecutionEngine/JIT/JIT.cpp
index 386c3be..0490343 100644
--- a/lib/ExecutionEngine/JIT/JIT.cpp
+++ b/lib/ExecutionEngine/JIT/JIT.cpp
@@ -580,8 +580,8 @@ void *JIT::getPointerToFunction(Function *F) {
   }
 
   if (F->isDeclaration()) {
-    bool AbortOnFailure = !areDlsymStubsEnabled() &&
-                          F->getLinkage() != GlobalValue::ExternalWeakLinkage;
+    bool AbortOnFailure =
+      !areDlsymStubsEnabled() && !F->hasExternalWeakLinkage();
     void *Addr = getPointerToNamedFunction(F->getName(), AbortOnFailure);
     addGlobalMapping(F, Addr);
     return Addr;
diff --git a/lib/Linker/LinkModules.cpp b/lib/Linker/LinkModules.cpp
index c596812..6ea3005 100644
--- a/lib/Linker/LinkModules.cpp
+++ b/lib/Linker/LinkModules.cpp
@@ -460,7 +460,7 @@ static bool GetLinkageResult(GlobalValue *Dest, const GlobalValue *Src,
         LT = Src->getLinkage();
       }
     } else if (Dest->hasExternalWeakLinkage()) {
-      //If the Dest is weak, use the source linkage
+      // If the Dest is weak, use the source linkage.
       LinkFromSrc = true;
       LT = Src->getLinkage();
     } else {
@@ -683,15 +683,22 @@ static bool LinkGlobals(Module *Dest, const Module *Src,
 
 static GlobalValue::LinkageTypes
 CalculateAliasLinkage(const GlobalValue *SGV, const GlobalValue *DGV) {
-  if (SGV->hasExternalLinkage() || DGV->hasExternalLinkage())
+  GlobalValue::LinkageTypes SL = SGV->getLinkage();
+  GlobalValue::LinkageTypes DL = DGV->getLinkage();
+  if (SL == GlobalValue::ExternalLinkage || DL == GlobalValue::ExternalLinkage)
     return GlobalValue::ExternalLinkage;
-  else if (SGV->hasWeakLinkage() || DGV->hasWeakLinkage())
-    return GlobalValue::WeakLinkage;
-  else if (SGV->hasInternalLinkage() && DGV->hasInternalLinkage())
+  else if (SL == GlobalValue::WeakAnyLinkage ||
+           DL == GlobalValue::WeakAnyLinkage)
+    return GlobalValue::WeakAnyLinkage;
+  else if (SL == GlobalValue::WeakODRLinkage ||
+           DL == GlobalValue::WeakODRLinkage)
+    return GlobalValue::WeakODRLinkage;
+  else if (SL == GlobalValue::InternalLinkage &&
+           DL == GlobalValue::InternalLinkage)
     return GlobalValue::InternalLinkage;
   else {
-    assert (SGV->hasPrivateLinkage() && DGV->hasPrivateLinkage() &&
-	    "Unexpected linkage type");
+    assert (SL == GlobalValue::PrivateLinkage &&
+            DL == GlobalValue::PrivateLinkage && "Unexpected linkage type");
     return GlobalValue::PrivateLinkage;
   }
 }
diff --git a/lib/Target/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp
index 41852fa..cc38efb 100644
--- a/lib/Target/ARM/ARMISelLowering.cpp
+++ b/lib/Target/ARM/ARMISelLowering.cpp
@@ -854,7 +854,7 @@ static bool GVIsIndirectSymbol(GlobalValue *GV, Reloc::Model RelocM) {
   bool isDecl = GV->isDeclaration() && !GV->hasNotBeenReadFromBitcode();
   if (GV->hasHiddenVisibility() && (!isDecl && !GV->hasCommonLinkage()))
     return false;
-  return RelocM != Reloc::Static && (isDecl || GV->mayBeOverridden());
+  return RelocM != Reloc::Static && (isDecl || GV->isWeakForLinker());
 }
 
 SDValue ARMTargetLowering::LowerGlobalAddressDarwin(SDValue Op,
diff --git a/lib/Target/ARM/AsmPrinter/ARMAsmPrinter.cpp b/lib/Target/ARM/AsmPrinter/ARMAsmPrinter.cpp
index 969b8fa..ae968e7 100644
--- a/lib/Target/ARM/AsmPrinter/ARMAsmPrinter.cpp
+++ b/lib/Target/ARM/AsmPrinter/ARMAsmPrinter.cpp
@@ -208,8 +208,10 @@ bool ARMAsmPrinter::runOnMachineFunction(MachineFunction &MF) {
     SwitchToTextSection("\t.text", F);
     O << "\t.globl\t" << CurrentFnName << "\n";
     break;
-  case Function::WeakLinkage:
-  case Function::LinkOnceLinkage:
+  case Function::WeakAnyLinkage:
+  case Function::WeakODRLinkage:
+  case Function::LinkOnceAnyLinkage:
+  case Function::LinkOnceODRLinkage:
     if (Subtarget->isTargetDarwin()) {
       SwitchToTextSection(
                 ".section __TEXT,__textcoal_nt,coalesced,pure_instructions", F);
@@ -853,7 +855,7 @@ void ARMAsmPrinter::printModuleLevelGV(const GlobalVariable* GVar) {
       }
     }
 
-    if (GVar->hasLocalLinkage() || GVar->mayBeOverridden()) {
+    if (GVar->hasLocalLinkage() || GVar->isWeakForLinker()) {
       if (Size == 0) Size = 1;   // .comm Foo, 0 is undefined, avoid it.
 
       if (isDarwin) {
@@ -899,9 +901,12 @@ void ARMAsmPrinter::printModuleLevelGV(const GlobalVariable* GVar) {
 
   SwitchToSection(TAI->SectionForGlobal(GVar));
   switch (GVar->getLinkage()) {
-   case GlobalValue::CommonLinkage:
-   case GlobalValue::LinkOnceLinkage:
-   case GlobalValue::WeakLinkage:
+   case GlobalValue::CommonAnyLinkage:
+   case GlobalValue::CommonODRLinkage:
+   case GlobalValue::LinkOnceAnyLinkage:
+   case GlobalValue::LinkOnceODRLinkage:
+   case GlobalValue::WeakAnyLinkage:
+   case GlobalValue::WeakODRLinkage:
     if (isDarwin) {
       O << "\t.globl " << name << "\n"
         << "\t.weak_definition " << name << "\n";
diff --git a/lib/Target/Alpha/AsmPrinter/AlphaAsmPrinter.cpp b/lib/Target/Alpha/AsmPrinter/AlphaAsmPrinter.cpp
index 536e592..5238b79 100644
--- a/lib/Target/Alpha/AsmPrinter/AlphaAsmPrinter.cpp
+++ b/lib/Target/Alpha/AsmPrinter/AlphaAsmPrinter.cpp
@@ -163,8 +163,10 @@ bool AlphaAsmPrinter::runOnMachineFunction(MachineFunction &MF) {
    case Function::ExternalLinkage:
      O << "\t.globl " << CurrentFnName << "\n";
      break;
-  case Function::WeakLinkage:
-  case Function::LinkOnceLinkage:
+  case Function::WeakAnyLinkage:
+  case Function::WeakODRLinkage:
+  case Function::LinkOnceAnyLinkage:
+  case Function::LinkOnceODRLinkage:
     O << TAI->getWeakRefDirective() << CurrentFnName << "\n";
     break;
   }
@@ -231,9 +233,12 @@ void AlphaAsmPrinter::printModuleLevelGV(const GlobalVariable* GVar) {
 
   // 2: Kind
   switch (GVar->getLinkage()) {
-   case GlobalValue::LinkOnceLinkage:
-   case GlobalValue::WeakLinkage:
-   case GlobalValue::CommonLinkage:
+   case GlobalValue::LinkOnceAnyLinkage:
+   case GlobalValue::LinkOnceODRLinkage:
+   case GlobalValue::WeakAnyLinkage:
+   case GlobalValue::WeakODRLinkage:
+   case GlobalValue::CommonAnyLinkage:
+   case GlobalValue::CommonODRLinkage:
     O << TAI->getWeakRefDirective() << name << '\n';
     break;
    case GlobalValue::AppendingLinkage:
diff --git a/lib/Target/CellSPU/AsmPrinter/SPUAsmPrinter.cpp b/lib/Target/CellSPU/AsmPrinter/SPUAsmPrinter.cpp
index f784d70..7731a90 100644
--- a/lib/Target/CellSPU/AsmPrinter/SPUAsmPrinter.cpp
+++ b/lib/Target/CellSPU/AsmPrinter/SPUAsmPrinter.cpp
@@ -445,8 +445,10 @@ LinuxAsmPrinter::runOnMachineFunction(MachineFunction &MF)
     O << "\t.global\t" << CurrentFnName << "\n"
       << "\t.type\t" << CurrentFnName << ", @function\n";
     break;
-  case Function::WeakLinkage:
-  case Function::LinkOnceLinkage:
+  case Function::WeakAnyLinkage:
+  case Function::WeakODRLinkage:
+  case Function::LinkOnceAnyLinkage:
+  case Function::LinkOnceODRLinkage:
     O << "\t.global\t" << CurrentFnName << "\n";
     O << "\t.weak_definition\t" << CurrentFnName << "\n";
     break;
@@ -534,7 +536,7 @@ void LinuxAsmPrinter::printModuleLevelGV(const GlobalVariable* GVar) {
   if (C->isNullValue() && /* FIXME: Verify correct */
       !GVar->hasSection() &&
       (GVar->hasLocalLinkage() || GVar->hasExternalLinkage() ||
-       GVar->mayBeOverridden())) {
+       GVar->isWeakForLinker())) {
       if (Size == 0) Size = 1;   // .comm Foo, 0 is undefined, avoid it.
 
       if (GVar->hasExternalLinkage()) {
@@ -555,9 +557,12 @@ void LinuxAsmPrinter::printModuleLevelGV(const GlobalVariable* GVar) {
 
   switch (GVar->getLinkage()) {
     // Should never be seen for the CellSPU platform...
-   case GlobalValue::LinkOnceLinkage:
-   case GlobalValue::WeakLinkage:
-   case GlobalValue::CommonLinkage:
+   case GlobalValue::LinkOnceAnyLinkage:
+   case GlobalValue::LinkOnceODRLinkage:
+   case GlobalValue::WeakAnyLinkage:
+   case GlobalValue::WeakODRLinkage:
+   case GlobalValue::CommonAnyLinkage:
+   case GlobalValue::CommonODRLinkage:
     O << "\t.global " << name << '\n'
       << "\t.type " << name << ", @object\n"
       << "\t.weak " << name << '\n';
diff --git a/lib/Target/CppBackend/CPPBackend.cpp b/lib/Target/CppBackend/CPPBackend.cpp
index dbe4f2d..48cf495 100644
--- a/lib/Target/CppBackend/CPPBackend.cpp
+++ b/lib/Target/CppBackend/CPPBackend.cpp
@@ -294,10 +294,14 @@ namespace {
       Out << "GlobalValue::InternalLinkage"; break;
     case GlobalValue::PrivateLinkage:
       Out << "GlobalValue::PrivateLinkage"; break;
-    case GlobalValue::LinkOnceLinkage:
-      Out << "GlobalValue::LinkOnceLinkage "; break;
-    case GlobalValue::WeakLinkage:
-      Out << "GlobalValue::WeakLinkage"; break;
+    case GlobalValue::LinkOnceAnyLinkage:
+      Out << "GlobalValue::LinkOnceAnyLinkage "; break;
+    case GlobalValue::LinkOnceODRLinkage:
+      Out << "GlobalValue::LinkOnceODRLinkage "; break;
+    case GlobalValue::WeakAnyLinkage:
+      Out << "GlobalValue::WeakAnyLinkage"; break;
+    case GlobalValue::WeakODRLinkage:
+      Out << "GlobalValue::WeakODRLinkage"; break;
     case GlobalValue::AppendingLinkage:
       Out << "GlobalValue::AppendingLinkage"; break;
     case GlobalValue::ExternalLinkage:
@@ -306,12 +310,16 @@ namespace {
       Out << "GlobalValue::DLLImportLinkage"; break;
     case GlobalValue::DLLExportLinkage:
       Out << "GlobalValue::DLLExportLinkage"; break;
-    case GlobalValue::ExternalWeakLinkage:
-      Out << "GlobalValue::ExternalWeakLinkage"; break;
+    case GlobalValue::ExternalWeakAnyLinkage:
+      Out << "GlobalValue::ExternalWeakAnyLinkage"; break;
+    case GlobalValue::ExternalWeakODRLinkage:
+      Out << "GlobalValue::ExternalWeakODRLinkage"; break;
     case GlobalValue::GhostLinkage:
       Out << "GlobalValue::GhostLinkage"; break;
-    case GlobalValue::CommonLinkage:
-      Out << "GlobalValue::CommonLinkage"; break;
+    case GlobalValue::CommonAnyLinkage:
+      Out << "GlobalValue::CommonAnyLinkage"; break;
+    case GlobalValue::CommonODRLinkage:
+      Out << "GlobalValue::CommonODRLinkage"; break;
     }
   }
 
diff --git a/lib/Target/DarwinTargetAsmInfo.cpp b/lib/Target/DarwinTargetAsmInfo.cpp
index cc05c09..927fdd2 100644
--- a/lib/Target/DarwinTargetAsmInfo.cpp
+++ b/lib/Target/DarwinTargetAsmInfo.cpp
@@ -75,7 +75,7 @@ DarwinTargetAsmInfo::emitUsedDirectiveFor(const GlobalValue* GV,
 const Section*
 DarwinTargetAsmInfo::SelectSectionForGlobal(const GlobalValue *GV) const {
   SectionKind::Kind Kind = SectionKindForGlobal(GV);
-  bool isWeak = GV->mayBeOverridden();
+  bool isWeak = GV->isWeakForLinker();
   bool isNonStatic = TM.getRelocationModel() != Reloc::Static;
 
   switch (Kind) {
diff --git a/lib/Target/ELFTargetAsmInfo.cpp b/lib/Target/ELFTargetAsmInfo.cpp
index 624b95c..3a2a00c 100644
--- a/lib/Target/ELFTargetAsmInfo.cpp
+++ b/lib/Target/ELFTargetAsmInfo.cpp
@@ -49,14 +49,16 @@ ELFTargetAsmInfo::SelectSectionForGlobal(const GlobalValue *GV) const {
      case Function::DLLExportLinkage:
      case Function::ExternalLinkage:
       return TextSection;
-     case Function::WeakLinkage:
-     case Function::LinkOnceLinkage:
+     case Function::WeakAnyLinkage:
+     case Function::WeakODRLinkage:
+     case Function::LinkOnceAnyLinkage:
+     case Function::LinkOnceODRLinkage:
       std::string Name = UniqueSectionForGlobal(GV, Kind);
       unsigned Flags = SectionFlagsForGlobal(GV, Name.c_str());
       return getNamedSection(Name.c_str(), Flags);
     }
   } else if (const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV)) {
-    if (GVar->mayBeOverridden()) {
+    if (GVar->isWeakForLinker()) {
       std::string Name = UniqueSectionForGlobal(GVar, Kind);
       unsigned Flags = SectionFlagsForGlobal(GVar, Name.c_str());
       return getNamedSection(Name.c_str(), Flags);
diff --git a/lib/Target/IA64/IA64AsmPrinter.cpp b/lib/Target/IA64/IA64AsmPrinter.cpp
index 0047430..d8ec210 100644
--- a/lib/Target/IA64/IA64AsmPrinter.cpp
+++ b/lib/Target/IA64/IA64AsmPrinter.cpp
@@ -278,7 +278,7 @@ void IA64AsmPrinter::printModuleLevelGV(const GlobalVariable* GVar) {
 
   if (C->isNullValue() && !GVar->hasSection()) {
     if (!GVar->isThreadLocal() &&
-        (GVar->hasLocalLinkage() || GVar->mayBeOverridden())) {
+        (GVar->hasLocalLinkage() || GVar->isWeakForLinker())) {
       if (Size == 0) Size = 1;   // .comm Foo, 0 is undefined, avoid it.
 
       if (GVar->hasLocalLinkage()) {
@@ -296,9 +296,12 @@ void IA64AsmPrinter::printModuleLevelGV(const GlobalVariable* GVar) {
   }
 
   switch (GVar->getLinkage()) {
-   case GlobalValue::LinkOnceLinkage:
-   case GlobalValue::CommonLinkage:
-   case GlobalValue::WeakLinkage:
+   case GlobalValue::LinkOnceAnyLinkage:
+   case GlobalValue::LinkOnceODRLinkage:
+   case GlobalValue::CommonAnyLinkage:
+   case GlobalValue::CommonODRLinkage:
+   case GlobalValue::WeakAnyLinkage:
+   case GlobalValue::WeakODRLinkage:
     // Nonnull linkonce -> weak
     O << "\t.weak " << name << '\n';
     break;
diff --git a/lib/Target/Mips/MipsAsmPrinter.cpp b/lib/Target/Mips/MipsAsmPrinter.cpp
index 732c5d7..a22d7d6 100644
--- a/lib/Target/Mips/MipsAsmPrinter.cpp
+++ b/lib/Target/Mips/MipsAsmPrinter.cpp
@@ -504,7 +504,7 @@ printModuleLevelGV(const GlobalVariable* GVar) {
 
   if (C->isNullValue() && !GVar->hasSection()) {
     if (!GVar->isThreadLocal() &&
-        (GVar->hasLocalLinkage() || GVar->mayBeOverridden())) {
+        (GVar->hasLocalLinkage() || GVar->isWeakForLinker())) {
       if (Size == 0) Size = 1;   // .comm Foo, 0 is undefined, avoid it.
 
       if (GVar->hasLocalLinkage())
@@ -519,9 +519,12 @@ printModuleLevelGV(const GlobalVariable* GVar) {
     }
   }
   switch (GVar->getLinkage()) {
-   case GlobalValue::LinkOnceLinkage:
-   case GlobalValue::CommonLinkage:
-   case GlobalValue::WeakLinkage:
+   case GlobalValue::LinkOnceAnyLinkage:
+   case GlobalValue::LinkOnceODRLinkage:
+   case GlobalValue::CommonAnyLinkage:
+   case GlobalValue::CommonODRLinkage:
+   case GlobalValue::WeakAnyLinkage:
+   case GlobalValue::WeakODRLinkage:
     // FIXME: Verify correct for weak.
     // Nonnull linkonce -> weak
     O << "\t.weak " << name << '\n';
diff --git a/lib/Target/Mips/MipsTargetAsmInfo.cpp b/lib/Target/Mips/MipsTargetAsmInfo.cpp
index 7566f41..3eee3be 100644
--- a/lib/Target/Mips/MipsTargetAsmInfo.cpp
+++ b/lib/Target/Mips/MipsTargetAsmInfo.cpp
@@ -85,7 +85,7 @@ SelectSectionForGlobal(const GlobalValue *GV) const {
   SectionKind::Kind K = SectionKindForGlobal(GV);
   const GlobalVariable *GVA = dyn_cast<GlobalVariable>(GV);
 
-  if (GVA && (!GVA->mayBeOverridden()))
+  if (GVA && (!GVA->isWeakForLinker()))
     switch (K) {
       case SectionKind::SmallData:
         return getSmallDataSection();
diff --git a/lib/Target/PowerPC/AsmPrinter/PPCAsmPrinter.cpp b/lib/Target/PowerPC/AsmPrinter/PPCAsmPrinter.cpp
index 57a2697..4da5377 100644
--- a/lib/Target/PowerPC/AsmPrinter/PPCAsmPrinter.cpp
+++ b/lib/Target/PowerPC/AsmPrinter/PPCAsmPrinter.cpp
@@ -388,7 +388,7 @@ void PPCAsmPrinter::printOp(const MachineOperand &MO) {
 
     // External or weakly linked global variables need non-lazily-resolved stubs
     if (TM.getRelocationModel() != Reloc::Static) {
-      if (GV->isDeclaration() || GV->mayBeOverridden()) {
+      if (GV->isDeclaration() || GV->isWeakForLinker()) {
         if (GV->hasHiddenVisibility()) {
           if (!GV->isDeclaration() && !GV->hasCommonLinkage())
             O << Name;
@@ -592,8 +592,10 @@ bool PPCLinuxAsmPrinter::runOnMachineFunction(MachineFunction &MF) {
     O << "\t.global\t" << CurrentFnName << '\n'
       << "\t.type\t" << CurrentFnName << ", @function\n";
     break;
-  case Function::WeakLinkage:
-  case Function::LinkOnceLinkage:
+  case Function::WeakAnyLinkage:
+  case Function::WeakODRLinkage:
+  case Function::LinkOnceAnyLinkage:
+  case Function::LinkOnceODRLinkage:
     O << "\t.global\t" << CurrentFnName << '\n';
     O << "\t.weak\t" << CurrentFnName << '\n';
     break;
@@ -689,7 +691,7 @@ void PPCLinuxAsmPrinter::printModuleLevelGV(const GlobalVariable* GVar) {
   if (C->isNullValue() && /* FIXME: Verify correct */
       !GVar->hasSection() &&
       (GVar->hasLocalLinkage() || GVar->hasExternalLinkage() ||
-       GVar->mayBeOverridden())) {
+       GVar->isWeakForLinker())) {
       if (Size == 0) Size = 1;   // .comm Foo, 0 is undefined, avoid it.
 
       if (GVar->hasExternalLinkage()) {
@@ -709,9 +711,12 @@ void PPCLinuxAsmPrinter::printModuleLevelGV(const GlobalVariable* GVar) {
   }
 
   switch (GVar->getLinkage()) {
-   case GlobalValue::LinkOnceLinkage:
-   case GlobalValue::WeakLinkage:
-   case GlobalValue::CommonLinkage:
+   case GlobalValue::LinkOnceAnyLinkage:
+   case GlobalValue::LinkOnceODRLinkage:
+   case GlobalValue::WeakAnyLinkage:
+   case GlobalValue::WeakODRLinkage:
+   case GlobalValue::CommonAnyLinkage:
+   case GlobalValue::CommonODRLinkage:
     O << "\t.global " << name << '\n'
       << "\t.type " << name << ", @object\n"
       << "\t.weak " << name << '\n';
@@ -785,8 +790,10 @@ bool PPCDarwinAsmPrinter::runOnMachineFunction(MachineFunction &MF) {
   case Function::ExternalLinkage:
     O << "\t.globl\t" << CurrentFnName << '\n';
     break;
-  case Function::WeakLinkage:
-  case Function::LinkOnceLinkage:
+  case Function::WeakAnyLinkage:
+  case Function::WeakODRLinkage:
+  case Function::LinkOnceAnyLinkage:
+  case Function::LinkOnceODRLinkage:
     O << "\t.globl\t" << CurrentFnName << '\n';
     O << "\t.weak_definition\t" << CurrentFnName << '\n';
     break;
@@ -918,7 +925,7 @@ void PPCDarwinAsmPrinter::printModuleLevelGV(const GlobalVariable* GVar) {
   if (C->isNullValue() && /* FIXME: Verify correct */
       !GVar->hasSection() &&
       (GVar->hasLocalLinkage() || GVar->hasExternalLinkage() ||
-       GVar->mayBeOverridden()) &&
+       GVar->isWeakForLinker()) &&
       TAI->SectionKindForGlobal(GVar) != SectionKind::RODataMergeStr) {
     if (Size == 0) Size = 1;   // .comm Foo, 0 is undefined, avoid it.
 
@@ -950,9 +957,12 @@ void PPCDarwinAsmPrinter::printModuleLevelGV(const GlobalVariable* GVar) {
   }
 
   switch (GVar->getLinkage()) {
-   case GlobalValue::LinkOnceLinkage:
-   case GlobalValue::WeakLinkage:
-   case GlobalValue::CommonLinkage:
+   case GlobalValue::LinkOnceAnyLinkage:
+   case GlobalValue::LinkOnceODRLinkage:
+   case GlobalValue::WeakAnyLinkage:
+   case GlobalValue::WeakODRLinkage:
+   case GlobalValue::CommonAnyLinkage:
+   case GlobalValue::CommonODRLinkage:
     O << "\t.globl " << name << '\n'
       << "\t.weak_definition " << name << '\n';
     break;
diff --git a/lib/Target/Sparc/AsmPrinter/SparcAsmPrinter.cpp b/lib/Target/Sparc/AsmPrinter/SparcAsmPrinter.cpp
index 80976bb..e0785d5 100644
--- a/lib/Target/Sparc/AsmPrinter/SparcAsmPrinter.cpp
+++ b/lib/Target/Sparc/AsmPrinter/SparcAsmPrinter.cpp
@@ -260,7 +260,7 @@ void SparcAsmPrinter::printModuleLevelGV(const GlobalVariable* GVar) {
 
   if (C->isNullValue() && !GVar->hasSection()) {
     if (!GVar->isThreadLocal() &&
-        (GVar->hasLocalLinkage() || GVar->mayBeOverridden())) {
+        (GVar->hasLocalLinkage() || GVar->isWeakForLinker())) {
       if (Size == 0) Size = 1;   // .comm Foo, 0 is undefined, avoid it.
 
       if (GVar->hasLocalLinkage())
@@ -276,9 +276,12 @@ void SparcAsmPrinter::printModuleLevelGV(const GlobalVariable* GVar) {
   }
 
   switch (GVar->getLinkage()) {
-   case GlobalValue::CommonLinkage:
-   case GlobalValue::LinkOnceLinkage:
-   case GlobalValue::WeakLinkage:   // FIXME: Verify correct for weak.
+   case GlobalValue::CommonAnyLinkage:
+   case GlobalValue::CommonODRLinkage:
+   case GlobalValue::LinkOnceAnyLinkage:
+   case GlobalValue::LinkOnceODRLinkage:
+   case GlobalValue::WeakAnyLinkage: // FIXME: Verify correct for weak.
+   case GlobalValue::WeakODRLinkage: // FIXME: Verify correct for weak.
     // Nonnull linkonce -> weak
     O << "\t.weak " << name << '\n';
     break;
diff --git a/lib/Target/TargetAsmInfo.cpp b/lib/Target/TargetAsmInfo.cpp
index d687e2f..8f5941f 100644
--- a/lib/Target/TargetAsmInfo.cpp
+++ b/lib/Target/TargetAsmInfo.cpp
@@ -259,7 +259,7 @@ TargetAsmInfo::SectionFlagsForGlobal(const GlobalValue *GV,
       assert(0 && "Unexpected section kind!");
     }
 
-    if (GV->mayBeOverridden())
+    if (GV->isWeakForLinker())
       Flags |= SectionFlags::Linkonce;
   }
 
@@ -310,7 +310,7 @@ const Section*
 TargetAsmInfo::SelectSectionForGlobal(const GlobalValue *GV) const {
   SectionKind::Kind Kind = SectionKindForGlobal(GV);
 
-  if (GV->mayBeOverridden()) {
+  if (GV->isWeakForLinker()) {
     std::string Name = UniqueSectionForGlobal(GV, Kind);
     unsigned Flags = SectionFlagsForGlobal(GV, Name.c_str());
     return getNamedSection(Name.c_str(), Flags);
diff --git a/lib/Target/X86/AsmPrinter/X86ATTAsmPrinter.cpp b/lib/Target/X86/AsmPrinter/X86ATTAsmPrinter.cpp
index 0595b6f..e3b6c27 100644
--- a/lib/Target/X86/AsmPrinter/X86ATTAsmPrinter.cpp
+++ b/lib/Target/X86/AsmPrinter/X86ATTAsmPrinter.cpp
@@ -168,8 +168,10 @@ void X86ATTAsmPrinter::emitFunctionHeader(const MachineFunction &MF) {
     EmitAlignment(FnAlign, F);
     O << "\t.globl\t" << CurrentFnName << '\n';
     break;
-  case Function::LinkOnceLinkage:
-  case Function::WeakLinkage:
+  case Function::LinkOnceAnyLinkage:
+  case Function::LinkOnceODRLinkage:
+  case Function::WeakAnyLinkage:
+  case Function::WeakODRLinkage:
     EmitAlignment(FnAlign, F);
     if (Subtarget->isTargetDarwin()) {
       O << "\t.globl\t" << CurrentFnName << '\n';
@@ -198,8 +200,7 @@ void X86ATTAsmPrinter::emitFunctionHeader(const MachineFunction &MF) {
   O << CurrentFnName << ":\n";
   // Add some workaround for linkonce linkage on Cygwin\MinGW
   if (Subtarget->isTargetCygMing() &&
-      (F->getLinkage() == Function::LinkOnceLinkage ||
-       F->getLinkage() == Function::WeakLinkage))
+      (F->hasLinkOnceLinkage() || F->hasWeakLinkage()))
     O << "Lllvm$workaround$fake$stub$" << CurrentFnName << ":\n";
 }
 
@@ -386,7 +387,7 @@ void X86ATTAsmPrinter::printOperand(const MachineInstr *MI, unsigned OpNo,
     if (shouldPrintStub(TM, Subtarget)) {
       // Link-once, declaration, or Weakly-linked global variables need
       // non-lazily-resolved stubs
-      if (GV->isDeclaration() || GV->mayBeOverridden()) {
+      if (GV->isDeclaration() || GV->isWeakForLinker()) {
         // Dynamically-resolved functions need a stub for the function.
         if (isCallOp && isa<Function>(GV)) {
           // Function stubs are no longer needed for Mac OS X 10.5 and up.
@@ -816,7 +817,7 @@ void X86ATTAsmPrinter::printModuleLevelGV(const GlobalVariable* GVar) {
     }
 
     if (!GVar->isThreadLocal() &&
-        (GVar->hasLocalLinkage() || GVar->mayBeOverridden())) {
+        (GVar->hasLocalLinkage() || GVar->isWeakForLinker())) {
       if (Size == 0) Size = 1;   // .comm Foo, 0 is undefined, avoid it.
 
       if (TAI->getLCOMMDirective() != NULL) {
@@ -855,9 +856,12 @@ void X86ATTAsmPrinter::printModuleLevelGV(const GlobalVariable* GVar) {
   }
 
   switch (GVar->getLinkage()) {
-  case GlobalValue::CommonLinkage:
-  case GlobalValue::LinkOnceLinkage:
-  case GlobalValue::WeakLinkage:
+  case GlobalValue::CommonAnyLinkage:
+  case GlobalValue::CommonODRLinkage:
+  case GlobalValue::LinkOnceAnyLinkage:
+  case GlobalValue::LinkOnceODRLinkage:
+  case GlobalValue::WeakAnyLinkage:
+  case GlobalValue::WeakODRLinkage:
     if (Subtarget->isTargetDarwin()) {
       O << "\t.globl " << name << '\n'
         << TAI->getWeakDefDirective() << name << '\n';
diff --git a/lib/Target/X86/AsmPrinter/X86IntelAsmPrinter.cpp b/lib/Target/X86/AsmPrinter/X86IntelAsmPrinter.cpp
index c4389aa..12b9c2f 100644
--- a/lib/Target/X86/AsmPrinter/X86IntelAsmPrinter.cpp
+++ b/lib/Target/X86/AsmPrinter/X86IntelAsmPrinter.cpp
@@ -455,9 +455,12 @@ bool X86IntelAsmPrinter::doFinalization(Module &M) {
     bool bCustomSegment = false;
 
     switch (I->getLinkage()) {
-    case GlobalValue::CommonLinkage:
-    case GlobalValue::LinkOnceLinkage:
-    case GlobalValue::WeakLinkage:
+    case GlobalValue::CommonAnyLinkage:
+    case GlobalValue::CommonODRLinkage:
+    case GlobalValue::LinkOnceAnyLinkage:
+    case GlobalValue::LinkOnceODRLinkage:
+    case GlobalValue::WeakAnyLinkage:
+    case GlobalValue::WeakODRLinkage:
       SwitchToDataSection("");
       O << name << "?\tsegment common 'COMMON'\n";
       bCustomSegment = true;
diff --git a/lib/Target/X86/X86Subtarget.cpp b/lib/Target/X86/X86Subtarget.cpp
index 6d2602a..8c5176b 100644
--- a/lib/Target/X86/X86Subtarget.cpp
+++ b/lib/Target/X86/X86Subtarget.cpp
@@ -51,7 +51,7 @@ bool X86Subtarget::GVRequiresExtraLoad(const GlobalValue* GV,
         // target is x86-64 or the symbol is definitely defined in the current
         // translation unit.
         return false;
-      return !isDirectCall && (isDecl || GV->mayBeOverridden());
+      return !isDirectCall && (isDecl || GV->isWeakForLinker());
     } else if (isTargetELF()) {
       // Extra load is needed for all externally visible.
       if (isDirectCall)
diff --git a/lib/Target/XCore/XCoreAsmPrinter.cpp b/lib/Target/XCore/XCoreAsmPrinter.cpp
index 3a30f10..6026e12 100644
--- a/lib/Target/XCore/XCoreAsmPrinter.cpp
+++ b/lib/Target/XCore/XCoreAsmPrinter.cpp
@@ -188,8 +188,10 @@ emitGlobal(const GlobalVariable *GV)
     case GlobalValue::AppendingLinkage:
       cerr << "AppendingLinkage is not supported by this target!\n";
       abort();
-    case GlobalValue::LinkOnceLinkage:
-    case GlobalValue::WeakLinkage:
+    case GlobalValue::LinkOnceAnyLinkage:
+    case GlobalValue::LinkOnceODRLinkage:
+    case GlobalValue::WeakAnyLinkage:
+    case GlobalValue::WeakODRLinkage:
     case GlobalValue::ExternalLinkage:
       emitArrayBound(name, GV);
       emitGlobalDirective(name);
@@ -266,8 +268,10 @@ emitFunctionStart(MachineFunction &MF)
   case Function::ExternalLinkage:
     emitGlobalDirective(CurrentFnName);
     break;
-  case Function::LinkOnceLinkage:
-  case Function::WeakLinkage:
+  case Function::LinkOnceAnyLinkage:
+  case Function::LinkOnceODRLinkage:
+  case Function::WeakAnyLinkage:
+  case Function::WeakODRLinkage:
     // TODO Use COMDAT groups for LinkOnceLinkage
     O << TAI->getGlobalDirective() << CurrentFnName << "\n";
     O << TAI->getWeakDefDirective() << CurrentFnName << "\n";
@@ -434,7 +438,8 @@ bool XCoreAsmPrinter::doInitialization(Module &M) {
       switch (I->getLinkage()) {
       default:
         assert(0 && "Unexpected linkage");
-      case Function::ExternalWeakLinkage:
+      case Function::ExternalWeakAnyLinkage:
+      case Function::ExternalWeakODRLinkage:
         ExtWeakSymbols.insert(I);
         // fallthrough
       case Function::ExternalLinkage:
diff --git a/lib/Target/XCore/XCoreTargetAsmInfo.cpp b/lib/Target/XCore/XCoreTargetAsmInfo.cpp
index 847224c..78eb90c 100644
--- a/lib/Target/XCore/XCoreTargetAsmInfo.cpp
+++ b/lib/Target/XCore/XCoreTargetAsmInfo.cpp
@@ -73,7 +73,7 @@ XCoreTargetAsmInfo::SelectSectionForGlobal(const GlobalValue *GV) const {
 
   if (const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV))
   {
-    if (!GVar->mayBeOverridden()) {
+    if (!GVar->isWeakForLinker()) {
       switch (Kind) {
       case SectionKind::RODataMergeStr:
         return MergeableStringSection(GVar);
diff --git a/lib/Transforms/IPO/IndMemRemoval.cpp b/lib/Transforms/IPO/IndMemRemoval.cpp
index 6b1f969..b55dea2 100644
--- a/lib/Transforms/IPO/IndMemRemoval.cpp
+++ b/lib/Transforms/IPO/IndMemRemoval.cpp
@@ -53,7 +53,7 @@ bool IndMemRemPass::runOnModule(Module &M) {
   if (Function* F = M.getFunction("free")) {
     if (F->isDeclaration() && F->arg_size() == 1 && !F->use_empty()) {
       Function* FN = Function::Create(F->getFunctionType(),
-                                      GlobalValue::LinkOnceLinkage,
+                                      GlobalValue::LinkOnceAnyLinkage,
                                       "free_llvm_bounce", &M);
       BasicBlock* bb = BasicBlock::Create("entry",FN);
       Instruction* R = ReturnInst::Create(bb);
@@ -67,7 +67,7 @@ bool IndMemRemPass::runOnModule(Module &M) {
   if (Function* F = M.getFunction("malloc")) {
     if (F->isDeclaration() && F->arg_size() == 1 && !F->use_empty()) {
       Function* FN = Function::Create(F->getFunctionType(), 
-                                      GlobalValue::LinkOnceLinkage, 
+                                      GlobalValue::LinkOnceAnyLinkage,
                                       "malloc_llvm_bounce", &M);
       FN->setDoesNotAlias(0);
       BasicBlock* bb = BasicBlock::Create("entry",FN);
diff --git a/lib/Transforms/Utils/InlineCost.cpp b/lib/Transforms/Utils/InlineCost.cpp
index b9f13d9..209ba92 100644
--- a/lib/Transforms/Utils/InlineCost.cpp
+++ b/lib/Transforms/Utils/InlineCost.cpp
@@ -182,12 +182,9 @@ InlineCost InlineCostAnalyzer::getInlineCost(CallSite CS,
 
       // Don't inline functions which can be redefined at link-time to mean
       // something else.
-      // FIXME: We allow link-once linkage since in practice all versions of
-      // the function have the same body (C++ ODR) - but the LLVM definition
-      // of LinkOnceLinkage doesn't require this.
-   if ((Callee->mayBeOverridden() && !Callee->hasLinkOnceLinkage()) ||
-      // Don't inline functions marked noinline.
-      Callee->hasFnAttr(Attribute::NoInline) || NeverInline.count(Callee))
+   if (Callee->mayBeOverridden() ||
+       // Don't inline functions marked noinline.
+       Callee->hasFnAttr(Attribute::NoInline) || NeverInline.count(Callee))
     return llvm::InlineCost::getNever();
 
   // InlineCost - This value measures how good of an inline candidate this call
diff --git a/lib/Transforms/Utils/LowerInvoke.cpp b/lib/Transforms/Utils/LowerInvoke.cpp
index 20cff90..b0364ec 100644
--- a/lib/Transforms/Utils/LowerInvoke.cpp
+++ b/lib/Transforms/Utils/LowerInvoke.cpp
@@ -139,7 +139,7 @@ bool LowerInvoke::doInitialization(Module &M) {
     // already exists.
     if (!(JBListHead = M.getGlobalVariable("llvm.sjljeh.jblist", PtrJBList))) {
       JBListHead = new GlobalVariable(PtrJBList, false,
-                                      GlobalValue::LinkOnceLinkage,
+                                      GlobalValue::LinkOnceAnyLinkage,
                                       Constant::getNullValue(PtrJBList),
                                       "llvm.sjljeh.jblist", &M);
     }
diff --git a/lib/VMCore/AsmWriter.cpp b/lib/VMCore/AsmWriter.cpp
index 239760d..12a8ed6 100644
--- a/lib/VMCore/AsmWriter.cpp
+++ b/lib/VMCore/AsmWriter.cpp
@@ -1183,22 +1183,26 @@ void AssemblyWriter::printModule(const Module *M) {
 
 static void PrintLinkage(GlobalValue::LinkageTypes LT, raw_ostream &Out) {
   switch (LT) {
-  case GlobalValue::PrivateLinkage:      Out << "private "; break;
-  case GlobalValue::InternalLinkage:     Out << "internal "; break;
-  case GlobalValue::LinkOnceLinkage:     Out << "linkonce "; break;
-  case GlobalValue::WeakLinkage:         Out << "weak "; break;
-  case GlobalValue::CommonLinkage:       Out << "common "; break;
-  case GlobalValue::AppendingLinkage:    Out << "appending "; break;
-  case GlobalValue::DLLImportLinkage:    Out << "dllimport "; break;
-  case GlobalValue::DLLExportLinkage:    Out << "dllexport "; break;
-  case GlobalValue::ExternalWeakLinkage: Out << "extern_weak "; break;      
+  case GlobalValue::PrivateLinkage:     Out << "private "; break;
+  case GlobalValue::InternalLinkage:    Out << "internal "; break;
+  case GlobalValue::LinkOnceAnyLinkage: Out << "linkonce "; break;
+  case GlobalValue::LinkOnceODRLinkage: Out << "linkonce_odr "; break;
+  case GlobalValue::WeakAnyLinkage:     Out << "weak "; break;
+  case GlobalValue::WeakODRLinkage:     Out << "weak_odr "; break;
+  case GlobalValue::CommonAnyLinkage:   Out << "common "; break;
+  case GlobalValue::CommonODRLinkage:   Out << "common_odr "; break;
+  case GlobalValue::AppendingLinkage:   Out << "appending "; break;
+  case GlobalValue::DLLImportLinkage:   Out << "dllimport "; break;
+  case GlobalValue::DLLExportLinkage:   Out << "dllexport "; break;
+  case GlobalValue::ExternalWeakAnyLinkage: Out << "extern_weak "; break;
+  case GlobalValue::ExternalWeakODRLinkage: Out << "extern_weak_odr "; break;
   case GlobalValue::ExternalLinkage: break;
   case GlobalValue::GhostLinkage:
     Out << "GhostLinkage not allowed in AsmWriter!\n";
     abort();
   }
 }
-      
+
 
 static void PrintVisibility(GlobalValue::VisibilityTypes Vis,
                             raw_ostream &Out) {