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 @@
     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 @@
     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 @@
 
         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 @@
           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 @@
         // 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 @@
     // 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 @@
 
     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 @@
       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 @@
       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 @@
 
       if (C->isNullValue() &&
           (I->hasLinkOnceLinkage() || I->hasInternalLinkage() ||
+           I->hasCommonLinkage() ||
            I->hasWeakLinkage() /* FIXME: Verify correct */)) {
         SwitchToDataSection(".data", I);
         if (I->hasInternalLinkage()) {
@@ -289,6 +290,7 @@
       } 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 @@
 
       // 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 @@
         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 @@
 
       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 @@
         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 @@
     // 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 @@
     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 @@
       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 @@
     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 @@
       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 @@
       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 @@
         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 @@
       // 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 @@
       
       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 @@
     }
 
     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 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 @@
     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.