Add CommonLinkage; currently tentative definitions

are represented as "weak", but there are subtle differences
in some cases on Darwin, so we need both.  The intent
is that "common" will behave identically to "weak" unless
somebody changes their target to do something else.
No functional change as yet.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@51118 91177308-0d34-0410-b5e6-96231b3b80d8

21 files changed, 67 insertions, 30 deletions

diff --git a/lib/AsmParser/LLLexer.cpp b/lib/AsmParser/LLLexer.cpp
index 6787ba1..37032eb 100644
--- a/lib/AsmParser/LLLexer.cpp
+++ b/lib/AsmParser/LLLexer.cpp
@@ -451,6 +451,7 @@ int LLLexer::LexIdentifier() {
   KEYWORD("appending", APPENDING);
   KEYWORD("dllimport", DLLIMPORT);
   KEYWORD("dllexport", DLLEXPORT);
+  KEYWORD("common", COMMON);
   KEYWORD("hidden", HIDDEN);
   KEYWORD("protected", PROTECTED);
   KEYWORD("extern_weak", EXTERN_WEAK);
diff --git a/lib/Bitcode/Reader/BitcodeReader.cpp b/lib/Bitcode/Reader/BitcodeReader.cpp
index 4098266..2d421b4 100644
--- a/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -66,6 +66,7 @@ static GlobalValue::LinkageTypes GetDecodedLinkage(unsigned Val) {
   case 5: return GlobalValue::DLLImportLinkage;
   case 6: return GlobalValue::DLLExportLinkage;
   case 7: return GlobalValue::ExternalWeakLinkage;
+  case 8: return GlobalValue::CommonLinkage;
   }
 }
 
diff --git a/lib/Bitcode/Writer/BitcodeWriter.cpp b/lib/Bitcode/Writer/BitcodeWriter.cpp
index 40e7011..8e9a395 100644
--- a/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -270,6 +270,7 @@ static unsigned getEncodedLinkage(const GlobalValue *GV) {
   case GlobalValue::DLLImportLinkage:    return 5;
   case GlobalValue::DLLExportLinkage:    return 6;
   case GlobalValue::ExternalWeakLinkage: return 7;
+  case GlobalValue::CommonLinkage:       return 8;
   }
 }
 
diff --git a/lib/CodeGen/ELFWriter.cpp b/lib/CodeGen/ELFWriter.cpp
index 63fee3a..27f23f4 100644
--- a/lib/CodeGen/ELFWriter.cpp
+++ b/lib/CodeGen/ELFWriter.cpp
@@ -282,7 +282,8 @@ void ELFWriter::EmitGlobal(GlobalVariable *GV) {
     // If this global is part of the common block, add it now.  Variables are
     // part of the common block if they are zero initialized and allowed to be
     // merged with other symbols.
-    if (GV->hasLinkOnceLinkage() || GV->hasWeakLinkage()) {
+    if (GV->hasLinkOnceLinkage() || GV->hasWeakLinkage() ||
+        GV->hasCommonLinkage()) {
       ELFSym CommonSym(GV);
       // Value for common symbols is the alignment required.
       CommonSym.Value = Align;
@@ -313,7 +314,7 @@ void ELFWriter::EmitGlobal(GlobalVariable *GV) {
     BSSSym.SetType(ELFSym::STT_OBJECT);
 
     switch (GV->getLinkage()) {
-    default:  // weak/linkonce handled above
+    default:  // weak/linkonce/common handled above
       assert(0 && "Unexpected linkage type!");
     case GlobalValue::AppendingLinkage:  // FIXME: This should be improved!
     case GlobalValue::ExternalLinkage:
diff --git a/lib/CodeGen/MachOWriter.cpp b/lib/CodeGen/MachOWriter.cpp
index 2726f70..c2b42ec 100644
--- a/lib/CodeGen/MachOWriter.cpp
+++ b/lib/CodeGen/MachOWriter.cpp
@@ -403,7 +403,8 @@ void MachOWriter::EmitGlobal(GlobalVariable *GV) {
     // If this global is part of the common block, add it now.  Variables are
     // part of the common block if they are zero initialized and allowed to be
     // merged with other symbols.
-    if (NoInit || GV->hasLinkOnceLinkage() || GV->hasWeakLinkage()) {
+    if (NoInit || GV->hasLinkOnceLinkage() || GV->hasWeakLinkage() ||
+        GV->hasCommonLinkage()) {
       MachOSym ExtOrCommonSym(GV, Mang->getValueName(GV), MachOSym::NO_SECT,TM);
       // For undefined (N_UNDF) external (N_EXT) types, n_value is the size in
       // bytes of the symbol.
@@ -951,6 +952,7 @@ MachOSym::MachOSym(const GlobalValue *gv, std::string name, uint8_t sect,
     break;
   case GlobalValue::WeakLinkage:
   case GlobalValue::LinkOnceLinkage:
+  case GlobalValue::CommonLinkage:
     assert(!isa<Function>(gv) && "Unexpected linkage type for Function!");
   case GlobalValue::ExternalLinkage:
     GVName = TAI->getGlobalPrefix() + name;
diff --git a/lib/ExecutionEngine/ExecutionEngine.cpp b/lib/ExecutionEngine/ExecutionEngine.cpp
index a56951d..8bd3b11 100644
--- a/lib/ExecutionEngine/ExecutionEngine.cpp
+++ b/lib/ExecutionEngine/ExecutionEngine.cpp
@@ -884,7 +884,7 @@ void ExecutionEngine::emitGlobals() {
           continue;
         
         // Otherwise, we know it's linkonce/weak, replace it if this is a strong
-        // symbol.
+        // symbol.  FIXME is this right for common?
         if (GV->hasExternalLinkage() || GVEntry->hasExternalWeakLinkage())
           GVEntry = GV;
       }
diff --git a/lib/Linker/LinkModules.cpp b/lib/Linker/LinkModules.cpp
index 3db5b09..cf4ceaa 100644
--- a/lib/Linker/LinkModules.cpp
+++ b/lib/Linker/LinkModules.cpp
@@ -410,10 +410,12 @@ static bool GetLinkageResult(GlobalValue *Dest, const GlobalValue *Src,
             "': can only link appending global with another appending global!");
     LinkFromSrc = true; // Special cased.
     LT = Src->getLinkage();
-  } else if (Src->hasWeakLinkage() || Src->hasLinkOnceLinkage()) {
-    // At this point we know that Dest has LinkOnce, External*, Weak, or
-    // DLL* linkage.
-    if ((Dest->hasLinkOnceLinkage() && Src->hasWeakLinkage()) ||
+  } else if (Src->hasWeakLinkage() || Src->hasLinkOnceLinkage() ||
+             Src->hasCommonLinkage()) {
+    // At this point we know that Dest has LinkOnce, External*, Weak, Common,
+    // or DLL* linkage.
+    if ((Dest->hasLinkOnceLinkage() && 
+          (Src->hasWeakLinkage() || Src->hasCommonLinkage())) ||
         Dest->hasExternalWeakLinkage()) {
       LinkFromSrc = true;
       LT = Src->getLinkage();
@@ -421,7 +423,8 @@ static bool GetLinkageResult(GlobalValue *Dest, const GlobalValue *Src,
       LinkFromSrc = false;
       LT = Dest->getLinkage();
     }
-  } else if (Dest->hasWeakLinkage() || Dest->hasLinkOnceLinkage()) {
+  } else if (Dest->hasWeakLinkage() || Dest->hasLinkOnceLinkage() ||
+             Dest->hasCommonLinkage()) {
     // At this point we know that Src has External* or DLL* linkage.
     if (Src->hasExternalWeakLinkage()) {
       LinkFromSrc = false;
@@ -792,10 +795,12 @@ static bool LinkGlobalInits(Module *Dest, const Module *Src,
           if (DGV->getInitializer() != SInit)
             return Error(Err, "Global Variable Collision on '" + SGV->getName() +
                          "': global variables have different initializers");
-        } else if (DGV->hasLinkOnceLinkage() || DGV->hasWeakLinkage()) {
+        } else if (DGV->hasLinkOnceLinkage() || DGV->hasWeakLinkage() ||
+                   DGV->hasCommonLinkage()) {
           // Nothing is required, mapped values will take the new global
           // automatically.
-        } else if (SGV->hasLinkOnceLinkage() || SGV->hasWeakLinkage()) {
+        } else if (SGV->hasLinkOnceLinkage() || SGV->hasWeakLinkage() ||
+                   SGV->hasCommonLinkage()) {
           // Nothing is required, mapped values will take the new global
           // automatically.
         } else if (DGV->hasAppendingLinkage()) {
@@ -916,16 +921,19 @@ static bool LinkFunctionProtos(Module *Dest, const Module *Src,
       DF->setLinkage(SF->getLinkage());
       // Visibility of prototype is overridden by vis of definition.
       DF->setVisibility(SF->getVisibility());
-    } else if (SF->hasWeakLinkage() || SF->hasLinkOnceLinkage()) {
+    } else if (SF->hasWeakLinkage() || SF->hasLinkOnceLinkage() ||
+               SF->hasCommonLinkage()) {
       // At this point we know that DF has LinkOnce, Weak, or External* linkage.
       ValueMap[SF] = DF;
 
       // Linkonce+Weak = Weak
       // *+External Weak = *
-      if ((DF->hasLinkOnceLinkage() && SF->hasWeakLinkage()) ||
+      if ((DF->hasLinkOnceLinkage() && 
+              (SF->hasWeakLinkage() || SF->hasCommonLinkage())) ||
           DF->hasExternalWeakLinkage())
         DF->setLinkage(SF->getLinkage());
-    } else if (DF->hasWeakLinkage() || DF->hasLinkOnceLinkage()) {
+    } else if (DF->hasWeakLinkage() || DF->hasLinkOnceLinkage() ||
+               DF->hasCommonLinkage()) {
       // At this point we know that SF has LinkOnce or External* linkage.
       ValueMap[SF] = DF;
       if (!SF->hasLinkOnceLinkage() && !SF->hasExternalWeakLinkage())
diff --git a/lib/Target/Alpha/AlphaAsmPrinter.cpp b/lib/Target/Alpha/AlphaAsmPrinter.cpp
index 42e4b78..2c28971 100644
--- a/lib/Target/Alpha/AlphaAsmPrinter.cpp
+++ b/lib/Target/Alpha/AlphaAsmPrinter.cpp
@@ -225,6 +225,7 @@ bool AlphaAsmPrinter::doFinalization(Module &M) {
     switch (I->getLinkage()) {
     case GlobalValue::LinkOnceLinkage:
     case GlobalValue::WeakLinkage:
+    case GlobalValue::CommonLinkage:
       O << TAI->getWeakRefDirective() << name << '\n';
       break;
     case GlobalValue::AppendingLinkage:
diff --git a/lib/Target/CBackend/CBackend.cpp b/lib/Target/CBackend/CBackend.cpp
index dcc920a..f52322b 100644
--- a/lib/Target/CBackend/CBackend.cpp
+++ b/lib/Target/CBackend/CBackend.cpp
@@ -1604,7 +1604,8 @@ bool CWriter::doInitialization(Module &M) {
     for (Module::global_iterator I = M.global_begin(), E = M.global_end();
          I != E; ++I) {
 
-      if (I->hasExternalLinkage() || I->hasExternalWeakLinkage())
+      if (I->hasExternalLinkage() || I->hasExternalWeakLinkage() || 
+          I->hasCommonLinkage())
         Out << "extern ";
       else if (I->hasDLLImportLinkage())
         Out << "__declspec(dllimport) ";
@@ -1678,6 +1679,8 @@ bool CWriter::doInitialization(Module &M) {
 
         if (I->hasLinkOnceLinkage())
           Out << " __attribute__((common))";
+        else if (I->hasCommonLinkage())     // FIXME is this right?
+          Out << " __ATTRIBUTE_WEAK__";
         else if (I->hasWeakLinkage())
           Out << " __ATTRIBUTE_WEAK__";
         else if (I->hasExternalWeakLinkage())
@@ -1715,6 +1718,8 @@ bool CWriter::doInitialization(Module &M) {
           Out << " __attribute__((common))";
         else if (I->hasWeakLinkage())
           Out << " __ATTRIBUTE_WEAK__";
+        else if (I->hasCommonLinkage())
+          Out << " __ATTRIBUTE_WEAK__";
 
         if (I->hasHiddenVisibility())
           Out << " __HIDDEN__";
@@ -1724,6 +1729,7 @@ bool CWriter::doInitialization(Module &M) {
         // this, however, occurs when the variable has weak linkage.  In this
         // case, the assembler will complain about the variable being both weak
         // and common, so we disable this optimization.
+        // FIXME common linkage should avoid this problem.
         if (!I->getInitializer()->isNullValue()) {
           Out << " = " ;
           writeOperand(I->getInitializer());
diff --git a/lib/Target/CellSPU/SPUAsmPrinter.cpp b/lib/Target/CellSPU/SPUAsmPrinter.cpp
index f627896..4e4324b 100644
--- a/lib/Target/CellSPU/SPUAsmPrinter.cpp
+++ b/lib/Target/CellSPU/SPUAsmPrinter.cpp
@@ -340,7 +340,7 @@ void SPUAsmPrinter::printOp(const MachineOperand &MO) {
     // stubs
     if (TM.getRelocationModel() != Reloc::Static) {
       if (((GV->isDeclaration() || GV->hasWeakLinkage() ||
-            GV->hasLinkOnceLinkage()))) {
+            GV->hasLinkOnceLinkage() || GV->hasCommonLinkage()))) {
         GVStubs.insert(Name);
         O << "L" << Name << "$non_lazy_ptr";
         return;
@@ -510,7 +510,7 @@ bool LinuxAsmPrinter::doFinalization(Module &M) {
 
     if (C->isNullValue() && /* FIXME: Verify correct */
         (I->hasInternalLinkage() || I->hasWeakLinkage() ||
-         I->hasLinkOnceLinkage() ||
+         I->hasLinkOnceLinkage() || I->hasCommonLinkage() ||
          (I->hasExternalLinkage() && !I->hasSection()))) {
       if (Size == 0) Size = 1;   // .comm Foo, 0 is undefined, avoid it.
       if (I->hasExternalLinkage()) {
@@ -537,6 +537,7 @@ bool LinuxAsmPrinter::doFinalization(Module &M) {
       switch (I->getLinkage()) {
       case GlobalValue::LinkOnceLinkage:
       case GlobalValue::WeakLinkage:
+      case GlobalValue::CommonLinkage:
         O << "\t.global " << name << '\n'
           << "\t.weak_definition " << name << '\n';
         SwitchToDataSection(".section __DATA,__datacoal_nt,coalesced", I);
diff --git a/lib/Target/CppBackend/CPPBackend.cpp b/lib/Target/CppBackend/CPPBackend.cpp
index 8724073..dc9a11e 100644
--- a/lib/Target/CppBackend/CPPBackend.cpp
+++ b/lib/Target/CppBackend/CPPBackend.cpp
@@ -301,6 +301,8 @@ namespace {
       Out << "GlobalValue::ExternalWeakLinkage"; break;
     case GlobalValue::GhostLinkage:
       Out << "GlobalValue::GhostLinkage"; break;
+    case GlobalValue::CommonLinkage:
+      Out << "GlobalValue::CommonLinkage"; break;
     }
   }
 
diff --git a/lib/Target/IA64/IA64AsmPrinter.cpp b/lib/Target/IA64/IA64AsmPrinter.cpp
index 829730d..037687c 100644
--- a/lib/Target/IA64/IA64AsmPrinter.cpp
+++ b/lib/Target/IA64/IA64AsmPrinter.cpp
@@ -275,6 +275,7 @@ bool IA64AsmPrinter::doFinalization(Module &M) {
 
       if (C->isNullValue() &&
           (I->hasLinkOnceLinkage() || I->hasInternalLinkage() ||
+           I->hasCommonLinkage() ||
            I->hasWeakLinkage() /* FIXME: Verify correct */)) {
         SwitchToDataSection(".data", I);
         if (I->hasInternalLinkage()) {
@@ -289,6 +290,7 @@ bool IA64AsmPrinter::doFinalization(Module &M) {
       } else {
         switch (I->getLinkage()) {
           case GlobalValue::LinkOnceLinkage:
+          case GlobalValue::CommonLinkage:
           case GlobalValue::WeakLinkage:   // FIXME: Verify correct for weak.
                                            // Nonnull linkonce -> weak
             O << "\t.weak " << name << "\n";
diff --git a/lib/Target/Mips/MipsAsmPrinter.cpp b/lib/Target/Mips/MipsAsmPrinter.cpp
index 6c0c908..6ae6104 100644
--- a/lib/Target/Mips/MipsAsmPrinter.cpp
+++ b/lib/Target/Mips/MipsAsmPrinter.cpp
@@ -461,7 +461,8 @@ doFinalization(Module &M)
 
       // Is this correct ?
       if (C->isNullValue() && (I->hasLinkOnceLinkage() || 
-          I->hasInternalLinkage() || I->hasWeakLinkage())) 
+          I->hasInternalLinkage() || I->hasWeakLinkage() ||
+          I->hasCommonLinkage()))
       {
         if (Size == 0) Size = 1;   // .comm Foo, 0 is undefined, avoid it.
 
@@ -487,7 +488,8 @@ doFinalization(Module &M)
         switch (I->getLinkage()) 
         {
           case GlobalValue::LinkOnceLinkage:
-          case GlobalValue::WeakLinkage:   
+          case GlobalValue::CommonLinkage:
+          case GlobalValue::WeakLinkage:
             // FIXME: Verify correct for weak.
             // Nonnull linkonce -> weak
             O << "\t.weak " << name << "\n";
diff --git a/lib/Target/PIC16/PIC16AsmPrinter.cpp b/lib/Target/PIC16/PIC16AsmPrinter.cpp
index f211fac..15711b5 100644
--- a/lib/Target/PIC16/PIC16AsmPrinter.cpp
+++ b/lib/Target/PIC16/PIC16AsmPrinter.cpp
@@ -414,7 +414,7 @@ bool PIC16AsmPrinter::doFinalization(Module &M)
 
       if (!I->hasSection() &&
           (I->hasInternalLinkage() || I->hasWeakLinkage() ||
-           I->hasLinkOnceLinkage())) {
+           I->hasLinkOnceLinkage() || I->hasCommonLinkage())) {
         if (Size == 0) Size = 1;   // .comm Foo, 0 is undefined, avoid it.
         if (!NoZerosInBSS && TAI->getBSSSection())
           SwitchToDataSection(M.getModuleIdentifier().c_str(), I);
diff --git a/lib/Target/PowerPC/PPCAsmPrinter.cpp b/lib/Target/PowerPC/PPCAsmPrinter.cpp
index 4cc9d2a..96e1ae8 100644
--- a/lib/Target/PowerPC/PPCAsmPrinter.cpp
+++ b/lib/Target/PowerPC/PPCAsmPrinter.cpp
@@ -185,7 +185,7 @@ namespace {
         if (MO.getType() == MachineOperand::MO_GlobalAddress) {
           GlobalValue *GV = MO.getGlobal();
           if (((GV->isDeclaration() || GV->hasWeakLinkage() ||
-                GV->hasLinkOnceLinkage()))) {
+                GV->hasLinkOnceLinkage() || GV->hasCommonLinkage()))) {
             // Dynamically-resolved functions need a stub for the function.
             std::string Name = Mang->getValueName(GV);
             FnStubs.insert(Name);
@@ -390,7 +390,7 @@ 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->hasWeakLinkage() ||
-            GV->hasLinkOnceLinkage()))) {
+            GV->hasLinkOnceLinkage() || GV->hasCommonLinkage()))) {
         GVStubs.insert(Name);
         O << "L" << Name << "$non_lazy_ptr";
         return;
@@ -671,8 +671,8 @@ bool LinuxAsmPrinter::doFinalization(Module &M) {
     unsigned Align = TD->getPreferredAlignmentLog(I);
 
     if (C->isNullValue() && /* FIXME: Verify correct */
-        !I->hasSection() &&
-        (I->hasInternalLinkage() || I->hasWeakLinkage() ||
+        !I->hasSection() && (I->hasCommonLinkage() ||
+         I->hasInternalLinkage() || I->hasWeakLinkage() ||
          I->hasLinkOnceLinkage() || I->hasExternalLinkage())) {
       if (Size == 0) Size = 1;   // .comm Foo, 0 is undefined, avoid it.
       if (I->hasExternalLinkage()) {
@@ -696,6 +696,7 @@ bool LinuxAsmPrinter::doFinalization(Module &M) {
       switch (I->getLinkage()) {
       case GlobalValue::LinkOnceLinkage:
       case GlobalValue::WeakLinkage:
+      case GlobalValue::CommonLinkage:
         O << "\t.global " << name << '\n'
           << "\t.type " << name << ", @object\n"
           << "\t.weak " << name << '\n';
@@ -936,8 +937,8 @@ bool DarwinAsmPrinter::doFinalization(Module &M) {
     unsigned Align = TD->getPreferredAlignmentLog(I);
 
     if (C->isNullValue() && /* FIXME: Verify correct */
-        !I->hasSection() &&
-        (I->hasInternalLinkage() || I->hasWeakLinkage() ||
+        !I->hasSection() && (I->hasCommonLinkage() ||
+         I->hasInternalLinkage() || I->hasWeakLinkage() ||
          I->hasLinkOnceLinkage() || I->hasExternalLinkage())) {
       if (Size == 0) Size = 1;   // .comm Foo, 0 is undefined, avoid it.
       if (I->hasExternalLinkage()) {
@@ -961,6 +962,7 @@ bool DarwinAsmPrinter::doFinalization(Module &M) {
       switch (I->getLinkage()) {
       case GlobalValue::LinkOnceLinkage:
       case GlobalValue::WeakLinkage:
+      case GlobalValue::CommonLinkage:
         O << "\t.globl " << name << '\n'
           << "\t.weak_definition " << name << '\n';
         SwitchToDataSection("\t.section __DATA,__datacoal_nt,coalesced", I);
diff --git a/lib/Target/Sparc/SparcAsmPrinter.cpp b/lib/Target/Sparc/SparcAsmPrinter.cpp
index 01bd092..2011ab9 100644
--- a/lib/Target/Sparc/SparcAsmPrinter.cpp
+++ b/lib/Target/Sparc/SparcAsmPrinter.cpp
@@ -231,8 +231,8 @@ bool SparcAsmPrinter::doFinalization(Module &M) {
       unsigned Size = TD->getABITypeSize(C->getType());
       unsigned Align = TD->getPreferredAlignment(I);
 
-      if (C->isNullValue() &&
-          (I->hasLinkOnceLinkage() || I->hasInternalLinkage() ||
+      if (C->isNullValue() && (I->hasCommonLinkage() ||
+           I->hasLinkOnceLinkage() || I->hasInternalLinkage() ||
            I->hasWeakLinkage() /* FIXME: Verify correct */)) {
         SwitchToDataSection(".data", I);
         if (I->hasInternalLinkage())
@@ -243,6 +243,7 @@ bool SparcAsmPrinter::doFinalization(Module &M) {
         O << "\n";
       } else {
         switch (I->getLinkage()) {
+        case GlobalValue::CommonLinkage:
         case GlobalValue::LinkOnceLinkage:
         case GlobalValue::WeakLinkage:   // FIXME: Verify correct for weak.
           // Nonnull linkonce -> weak
diff --git a/lib/Target/X86/X86ATTAsmPrinter.cpp b/lib/Target/X86/X86ATTAsmPrinter.cpp
index 6909da1..4659deb 100644
--- a/lib/Target/X86/X86ATTAsmPrinter.cpp
+++ b/lib/Target/X86/X86ATTAsmPrinter.cpp
@@ -309,7 +309,8 @@ void X86ATTAsmPrinter::printOperand(const MachineInstr *MI, unsigned OpNo,
       // non-lazily-resolved stubs
       if (GV->isDeclaration() ||
           GV->hasWeakLinkage() ||
-          GV->hasLinkOnceLinkage()) {
+          GV->hasLinkOnceLinkage() ||
+          GV->hasCommonLinkage()) {
         // Dynamically-resolved functions need a stub for the function.
         if (isCallOp && isa<Function>(GV)) {
           FnStubs.insert(Name);
diff --git a/lib/Target/X86/X86AsmPrinter.cpp b/lib/Target/X86/X86AsmPrinter.cpp
index e1bc65f..3898a9e 100644
--- a/lib/Target/X86/X86AsmPrinter.cpp
+++ b/lib/Target/X86/X86AsmPrinter.cpp
@@ -200,7 +200,7 @@ bool X86SharedAsmPrinter::doFinalization(Module &M) {
       
       if (!I->isThreadLocal() &&
           (I->hasInternalLinkage() || I->hasWeakLinkage() ||
-           I->hasLinkOnceLinkage())) {
+           I->hasLinkOnceLinkage() || I->hasCommonLinkage())) {
         if (Size == 0) Size = 1;   // .comm Foo, 0 is undefined, avoid it.
         if (!NoZerosInBSS && TAI->getBSSSection())
           SwitchToDataSection(TAI->getBSSSection(), I);
@@ -235,6 +235,7 @@ bool X86SharedAsmPrinter::doFinalization(Module &M) {
     }
 
     switch (I->getLinkage()) {
+    case GlobalValue::CommonLinkage:
     case GlobalValue::LinkOnceLinkage:
     case GlobalValue::WeakLinkage:
       if (Subtarget->isTargetDarwin()) {
diff --git a/lib/Target/X86/X86IntelAsmPrinter.cpp b/lib/Target/X86/X86IntelAsmPrinter.cpp
index ddd90cd..a1031bd 100644
--- a/lib/Target/X86/X86IntelAsmPrinter.cpp
+++ b/lib/Target/X86/X86IntelAsmPrinter.cpp
@@ -373,6 +373,7 @@ bool X86IntelAsmPrinter::doFinalization(Module &M) {
     bool bCustomSegment = false;
 
     switch (I->getLinkage()) {
+    case GlobalValue::CommonLinkage:
     case GlobalValue::LinkOnceLinkage:
     case GlobalValue::WeakLinkage:
       SwitchToDataSection("");
diff --git a/lib/Target/X86/X86Subtarget.cpp b/lib/Target/X86/X86Subtarget.cpp
index 98d80c8..23ceb9b 100644
--- a/lib/Target/X86/X86Subtarget.cpp
+++ b/lib/Target/X86/X86Subtarget.cpp
@@ -41,6 +41,7 @@ bool X86Subtarget::GVRequiresExtraLoad(const GlobalValue* GV,
     if (isTargetDarwin()) {
       return (!isDirectCall &&
               (GV->hasWeakLinkage() || GV->hasLinkOnceLinkage() ||
+               GV->hasCommonLinkage() ||
                (GV->isDeclaration() && !GV->hasNotBeenReadFromBitcode())));
     } else if (isTargetELF()) {
       // Extra load is needed for all non-statics.
diff --git a/lib/VMCore/AsmWriter.cpp b/lib/VMCore/AsmWriter.cpp
index 06bfc50..3d39553 100644
--- a/lib/VMCore/AsmWriter.cpp
+++ b/lib/VMCore/AsmWriter.cpp
@@ -930,6 +930,7 @@ void AssemblyWriter::printGlobal(const GlobalVariable *GV) {
   } else {
     switch (GV->getLinkage()) {
     case GlobalValue::InternalLinkage:     Out << "internal "; break;
+    case GlobalValue::CommonLinkage:       Out << "common "; break;
     case GlobalValue::LinkOnceLinkage:     Out << "linkonce "; break;
     case GlobalValue::WeakLinkage:         Out << "weak "; break;
     case GlobalValue::AppendingLinkage:    Out << "appending "; break;
@@ -1049,6 +1050,7 @@ void AssemblyWriter::printFunction(const Function *F) {
   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;