Add isCString() - returns true if a ConstantArray is a CString.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@31201 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Constants.h

@@ -334,6 +334,11 @@ public:
   /// ubyte, and if the elements of the array are all ConstantInt's.
   bool isString() const;
 
+  /// isCString - This method returns true if the array is a string (see
+  /// isString) and it ends in a null byte \0 and does not contains any other
+  /// null bytes except its terminator.
+  bool isCString() const;
+
   /// getAsString - If this array is isString(), then this method converts the
   /// array to an std::string and returns it.  Otherwise, it asserts out.
   ///

lib/VMCore/Constants.cpp

@@ -1073,6 +1073,19 @@ bool ConstantArray::isString() const {
   return true;
 }
 
+/// isCString - This method returns true if the array is a string (see
+/// isString) and it ends in a null byte \0 and does not contains any other
+/// null bytes except its terminator.
+bool ConstantArray::isCString() const {
+  if (!isString()) return false;
+  // This is safe because a ConstantArray cannot be a zero array.
+  for (unsigned i = 0, e = getNumOperands()-1; i != e; ++i)
+    if (cast<ConstantInt>(getOperand(i))->getZExtValue() == 0)
+      return false;
+  return true;
+}
+
+
 // getAsString - If the sub-element type of this array is either sbyte or ubyte,
 // then this method converts the array to an std::string and returns it.
 // Otherwise, it asserts out.