emit padding as undef values, take 2
merge also a few tests I had here for this feature, and FileCheck'ize one file

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@101535 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGExprConstant.cpp b/lib/CodeGen/CGExprConstant.cpp
index 7da7554..52e7d04 100644
--- a/lib/CodeGen/CGExprConstant.cpp
+++ b/lib/CodeGen/CGExprConstant.cpp
@@ -259,7 +259,7 @@
   if (NumBytes > 1)
     Ty = llvm::ArrayType::get(Ty, NumBytes);
 
-  llvm::Constant *C = llvm::Constant::getNullValue(Ty);
+  llvm::Constant *C = llvm::UndefValue::get(Ty);
   Elements.push_back(C);
   assert(getAlignment(C) == 1 && "Padding must have 1 byte alignment!");
 
@@ -297,7 +297,7 @@
       if (NumBytes > 1)
         Ty = llvm::ArrayType::get(Ty, NumBytes);
 
-      llvm::Constant *Padding = llvm::Constant::getNullValue(Ty);
+      llvm::Constant *Padding = llvm::UndefValue::get(Ty);
       PackedElements.push_back(Padding);
       ElementOffsetInBytes += getSizeInBytes(Padding);
     }
@@ -537,7 +537,7 @@
         if (NumPadBytes > 1)
           Ty = llvm::ArrayType::get(Ty, NumPadBytes);
 
-        Elts.push_back(llvm::Constant::getNullValue(Ty));
+        Elts.push_back(llvm::UndefValue::get(Ty));
         Types.push_back(Ty);
       }