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 deb5c9bbfb..a063aa53ba 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 fb491d3278..6f1d5eefe8 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 19f8415bba..90dd50743a 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 e3bc908b6e..efdc77af81 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 2ddfbe3a13..0fe6fc682c 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 5633f0ffad..fefffbedb6 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 5c4957aba1..9181216b5a 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 7cca74b1fb..ddc4e3588b 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 5b4de27b8a..56b1736b41 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 22c21578ec..5fe05a4e8f 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 7913c01963..a08dcb2e49 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 5a55760c7c..2402f81bb0 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 386c3beedd..0490343b86 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 c596812e0c..6ea3005e75 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 41852fa594..cc38efb9cc 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 969b8face4..ae968e7b09 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 536e5920f3..5238b79d9d 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 f784d70f44..7731a9023a 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::