diff --git a/lib/Bytecode/Writer/SlotCalculator.cpp b/lib/Bytecode/Writer/SlotCalculator.cpp
index 7b18a1dfd5a..d462bdd1e9f 100644
--- a/lib/Bytecode/Writer/SlotCalculator.cpp
+++ b/lib/Bytecode/Writer/SlotCalculator.cpp
@@ -146,7 +146,8 @@ void SlotCalculator::processModule() {
           TypePlane &Plane = Table[plane];
           unsigned FirstNonStringID = 0;
           for (unsigned i = 0, e = Plane.size(); i != e; ++i)
-            if (cast<ConstantArray>(Plane[i])->isString()) {
+            if (isa<ConstantAggregateZero>(Plane[i]) ||
+                cast<ConstantArray>(Plane[i])->isString()) {
               // Check to see if we have to shuffle this string around.  If not,
               // don't do anything.
               if (i != FirstNonStringID) {
diff --git a/lib/Linker/LinkModules.cpp b/lib/Linker/LinkModules.cpp
index 457a8b97b65..aa7720ece35 100644
--- a/lib/Linker/LinkModules.cpp
+++ b/lib/Linker/LinkModules.cpp
@@ -284,7 +284,8 @@ static Value *RemapOperand(const Value *In,
 
   // Check to see if it's a constant that we are interesting in transforming...
   if (const Constant *CPV = dyn_cast<Constant>(In)) {
-    if (!isa<DerivedType>(CPV->getType()) && !isa<ConstantExpr>(CPV))
+    if ((!isa<DerivedType>(CPV->getType()) && !isa<ConstantExpr>(CPV)) ||
+        isa<ConstantAggregateZero>(CPV))
       return const_cast<Constant*>(CPV);   // Simple constants stay identical...
 
     Constant *Result = 0;
@@ -796,12 +797,24 @@ static bool LinkAppendingVars(Module *M,
 
       // Merge the initializer...
       Inits.reserve(NewSize);
-      ConstantArray *I = cast<ConstantArray>(G1->getInitializer());
-      for (unsigned i = 0, e = T1->getNumElements(); i != e; ++i)
-        Inits.push_back(cast<Constant>(I->getValues()[i]));
-      I = cast<ConstantArray>(G2->getInitializer());
-      for (unsigned i = 0, e = T2->getNumElements(); i != e; ++i)
-        Inits.push_back(cast<Constant>(I->getValues()[i]));
+      if (ConstantArray *I = dyn_cast<ConstantArray>(G1->getInitializer())) {
+        for (unsigned i = 0, e = T1->getNumElements(); i != e; ++i)
+          Inits.push_back(cast<Constant>(I->getValues()[i]));
+      } else {
+        assert(isa<ConstantAggregateZero>(G1->getInitializer()));
+        Constant *CV = Constant::getNullValue(T1->getElementType());
+        for (unsigned i = 0, e = T1->getNumElements(); i != e; ++i)
+          Inits.push_back(CV);
+      }
+      if (ConstantArray *I = dyn_cast<ConstantArray>(G2->getInitializer())) {
+        for (unsigned i = 0, e = T2->getNumElements(); i != e; ++i)
+          Inits.push_back(cast<Constant>(I->getValues()[i]));
+      } else {
+        assert(isa<ConstantAggregateZero>(G2->getInitializer()));
+        Constant *CV = Constant::getNullValue(T2->getElementType());
+        for (unsigned i = 0, e = T2->getNumElements(); i != e; ++i)
+          Inits.push_back(CV);
+      }
       NG->setInitializer(ConstantArray::get(NewType, Inits));
       Inits.clear();
 
diff --git a/lib/Target/SparcV9/SparcV9AsmPrinter.cpp b/lib/Target/SparcV9/SparcV9AsmPrinter.cpp
index e87f6a2215a..40aa81cab00 100644
--- a/lib/Target/SparcV9/SparcV9AsmPrinter.cpp
+++ b/lib/Target/SparcV9/SparcV9AsmPrinter.cpp
@@ -387,8 +387,9 @@ void AsmPrinter::printConstantValueOnly(const Constant* CV,
     }
     assert(sizeSoFar == cvsLayout->StructSize &&
            "Layout of constant struct may be incorrect!");
-  }
-  else
+  } else if (isa<ConstantAggregateZero>(CV)) {
+    PrintZeroBytesToPad(Target.getTargetData().getTypeSize(CV->getType()));
+  } else
     printSingleConstantValue(CV);
 
   if (numPadBytesAfter)
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 85d580b8ce5..773441f5383 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -2088,11 +2088,13 @@ static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) {
   // addressing...
   for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i)
     if (ConstantUInt *CU = dyn_cast<ConstantUInt>(CE->getOperand(i))) {
-      ConstantStruct *CS = cast<ConstantStruct>(C);
+      ConstantStruct *CS = dyn_cast<ConstantStruct>(C);
+      if (CS == 0) return 0;
       if (CU->getValue() >= CS->getValues().size()) return 0;
       C = cast<Constant>(CS->getValues()[CU->getValue()]);
     } else if (ConstantSInt *CS = dyn_cast<ConstantSInt>(CE->getOperand(i))) {
-      ConstantArray *CA = cast<ConstantArray>(C);
+      ConstantArray *CA = dyn_cast<ConstantArray>(C);
+      if (CA == 0) return 0;
       if ((uint64_t)CS->getValue() >= CA->getValues().size()) return 0;
       C = cast<Constant>(CA->getValues()[CS->getValue()]);
     } else 
diff --git a/lib/Transforms/Scalar/SCCP.cpp b/lib/Transforms/Scalar/SCCP.cpp
index 4e5e5156bb7..8304e2e823b 100644
--- a/lib/Transforms/Scalar/SCCP.cpp
+++ b/lib/Transforms/Scalar/SCCP.cpp
@@ -689,14 +689,16 @@ static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) {
   // addressing...
   for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i)
     if (ConstantUInt *CU = dyn_cast<ConstantUInt>(CE->getOperand(i))) {
-      ConstantStruct *CS = cast<ConstantStruct>(C);
+      ConstantStruct *CS = dyn_cast<ConstantStruct>(C);
+      if (CS == 0) return 0;
       if (CU->getValue() >= CS->getValues().size()) return 0;
       C = cast<Constant>(CS->getValues()[CU->getValue()]);
     } else if (ConstantSInt *CS = dyn_cast<ConstantSInt>(CE->getOperand(i))) {
-      ConstantArray *CA = cast<ConstantArray>(C);
+      ConstantArray *CA = dyn_cast<ConstantArray>(C);
+      if (CA == 0) return 0;
       if ((uint64_t)CS->getValue() >= CA->getValues().size()) return 0;
       C = cast<Constant>(CA->getValues()[CS->getValue()]);
-    } else 
+    } else
       return 0;
   return C;
 }
diff --git a/lib/Transforms/Utils/Linker.cpp b/lib/Transforms/Utils/Linker.cpp
index 457a8b97b65..aa7720ece35 100644
--- a/lib/Transforms/Utils/Linker.cpp
+++ b/lib/Transforms/Utils/Linker.cpp
@@ -284,7 +284,8 @@ static Value *RemapOperand(const Value *In,
 
   // Check to see if it's a constant that we are interesting in transforming...
   if (const Constant *CPV = dyn_cast<Constant>(In)) {
-    if (!isa<DerivedType>(CPV->getType()) && !isa<ConstantExpr>(CPV))
+    if ((!isa<DerivedType>(CPV->getType()) && !isa<ConstantExpr>(CPV)) ||
+        isa<ConstantAggregateZero>(CPV))
       return const_cast<Constant*>(CPV);   // Simple constants stay identical...
 
     Constant *Result = 0;
@@ -796,12 +797,24 @@ static bool LinkAppendingVars(Module *M,
 
       // Merge the initializer...
       Inits.reserve(NewSize);
-      ConstantArray *I = cast<ConstantArray>(G1->getInitializer());
-      for (unsigned i = 0, e = T1->getNumElements(); i != e; ++i)
-        Inits.push_back(cast<Constant>(I->getValues()[i]));
-      I = cast<ConstantArray>(G2->getInitializer());
-      for (unsigned i = 0, e = T2->getNumElements(); i != e; ++i)
-        Inits.push_back(cast<Constant>(I->getValues()[i]));
+      if (ConstantArray *I = dyn_cast<ConstantArray>(G1->getInitializer())) {
+        for (unsigned i = 0, e = T1->getNumElements(); i != e; ++i)
+          Inits.push_back(cast<Constant>(I->getValues()[i]));
+      } else {
+        assert(isa<ConstantAggregateZero>(G1->getInitializer()));
+        Constant *CV = Constant::getNullValue(T1->getElementType());
+        for (unsigned i = 0, e = T1->getNumElements(); i != e; ++i)
+          Inits.push_back(CV);
+      }
+      if (ConstantArray *I = dyn_cast<ConstantArray>(G2->getInitializer())) {
+        for (unsigned i = 0, e = T2->getNumElements(); i != e; ++i)
+          Inits.push_back(cast<Constant>(I->getValues()[i]));
+      } else {
+        assert(isa<ConstantAggregateZero>(G2->getInitializer()));
+        Constant *CV = Constant::getNullValue(T2->getElementType());
+        for (unsigned i = 0, e = T2->getNumElements(); i != e; ++i)
+          Inits.push_back(CV);
+      }
       NG->setInitializer(ConstantArray::get(NewType, Inits));
       Inits.clear();
 
diff --git a/lib/Transforms/Utils/ValueMapper.cpp b/lib/Transforms/Utils/ValueMapper.cpp
index acc433a6ed2..2cb6a9d221d 100644
--- a/lib/Transforms/Utils/ValueMapper.cpp
+++ b/lib/Transforms/Utils/ValueMapper.cpp
@@ -28,7 +28,7 @@ Value *llvm::MapValue(const Value *V, std::map<const Value*, Value*> &VM) {
 
   if (Constant *C = const_cast<Constant*>(dyn_cast<Constant>(V))) {
     if (isa<ConstantIntegral>(C) || isa<ConstantFP>(C) ||
-        isa<ConstantPointerNull>(C))
+        isa<ConstantPointerNull>(C) || isa<ConstantAggregateZero>(C))
       return VMSlot = C;           // Primitive constants map directly
     else if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(C)) {
       GlobalValue *MV = cast<GlobalValue>(MapValue((Value*)CPR->getValue(),VM));
diff --git a/lib/VMCore/AsmWriter.cpp b/lib/VMCore/AsmWriter.cpp
index 5fc7a893c44..29adfd079ad 100644
--- a/lib/VMCore/AsmWriter.cpp
+++ b/lib/VMCore/AsmWriter.cpp
@@ -288,12 +288,9 @@ static void WriteConstantInt(std::ostream &Out, const Constant *CV,
            "assuming that double is 64 bits!");
     Out << "0x" << utohexstr(*(uint64_t*)Ptr);
 
+  } else if (isa<ConstantAggregateZero>(CV)) {
+    Out << "zeroinitializer";
   } else if (const ConstantArray *CA = dyn_cast<ConstantArray>(CV)) {
-    if (CA->getNumOperands() > 5 && CA->isNullValue()) {
-      Out << "zeroinitializer";
-      return;
-    }
-
     // As a special case, print the array as a string if it is an array of
     // ubytes or an array of sbytes with positive values.
     // 
@@ -339,11 +336,6 @@ static void WriteConstantInt(std::ostream &Out, const Constant *CV,
       Out << " ]";
     }
   } else if (const ConstantStruct *CS = dyn_cast<ConstantStruct>(CV)) {
-    if (CS->getNumOperands() > 5 && CS->isNullValue()) {
-      Out << "zeroinitializer";
-      return;
-    }
-
     Out << "{";
     if (CS->getNumOperands()) {
       Out << " ";
diff --git a/lib/VMCore/Linker.cpp b/lib/VMCore/Linker.cpp
index 457a8b97b65..aa7720ece35 100644
--- a/lib/VMCore/Linker.cpp
+++ b/lib/VMCore/Linker.cpp
@@ -284,7 +284,8 @@ static Value *RemapOperand(const Value *In,
 
   // Check to see if it's a constant that we are interesting in transforming...
   if (const Constant *CPV = dyn_cast<Constant>(In)) {
-    if (!isa<DerivedType>(CPV->getType()) && !isa<ConstantExpr>(CPV))
+    if ((!isa<DerivedType>(CPV->getType()) && !isa<ConstantExpr>(CPV)) ||
+        isa<ConstantAggregateZero>(CPV))
       return const_cast<Constant*>(CPV);   // Simple constants stay identical...
 
     Constant *Result = 0;
@@ -796,12 +797,24 @@ static bool LinkAppendingVars(Module *M,
 
       // Merge the initializer...
       Inits.reserve(NewSize);
-      ConstantArray *I = cast<ConstantArray>(G1->getInitializer());
-      for (unsigned i = 0, e = T1->getNumElements(); i != e; ++i)
-        Inits.push_back(cast<Constant>(I->getValues()[i]));
-      I = cast<ConstantArray>(G2->getInitializer());
-      for (unsigned i = 0, e = T2->getNumElements(); i != e; ++i)
-        Inits.push_back(cast<Constant>(I->getValues()[i]));
+      if (ConstantArray *I = dyn_cast<ConstantArray>(G1->getInitializer())) {
+        for (unsigned i = 0, e = T1->getNumElements(); i != e; ++i)
+          Inits.push_back(cast<Constant>(I->getValues()[i]));
+      } else {
+        assert(isa<ConstantAggregateZero>(G1->getInitializer()));
+        Constant *CV = Constant::getNullValue(T1->getElementType());
+        for (unsigned i = 0, e = T1->getNumElements(); i != e; ++i)
+          Inits.push_back(CV);
+      }
+      if (ConstantArray *I = dyn_cast<ConstantArray>(G2->getInitializer())) {
+        for (unsigned i = 0, e = T2->getNumElements(); i != e; ++i)
+          Inits.push_back(cast<Constant>(I->getValues()[i]));
+      } else {
+        assert(isa<ConstantAggregateZero>(G2->getInitializer()));
+        Constant *CV = Constant::getNullValue(T2->getElementType());
+        for (unsigned i = 0, e = T2->getNumElements(); i != e; ++i)
+          Inits.push_back(CV);
+      }
       NG->setInitializer(ConstantArray::get(NewType, Inits));
       Inits.clear();
 
diff --git a/lib/VMCore/SlotCalculator.cpp b/lib/VMCore/SlotCalculator.cpp
index 7b18a1dfd5a..d462bdd1e9f 100644
--- a/lib/VMCore/SlotCalculator.cpp
+++ b/lib/VMCore/SlotCalculator.cpp
@@ -146,7 +146,8 @@ void SlotCalculator::processModule() {
           TypePlane &Plane = Table[plane];
           unsigned FirstNonStringID = 0;
           for (unsigned i = 0, e = Plane.size(); i != e; ++i)
-            if (cast<ConstantArray>(Plane[i])->isString()) {
+            if (isa<ConstantAggregateZero>(Plane[i]) ||
+                cast<ConstantArray>(Plane[i])->isString()) {
               // Check to see if we have to shuffle this string around.  If not,
               // don't do anything.
               if (i != FirstNonStringID) {