PR10210: New method ConstantArray::getAsCString(). Use it in LTO to

avoid getting embedded trailing null bytes in std::strings.

llvm-svn: 133999

Author: jayfoad

llvm/include/llvm/Constants.h

@@ -387,6 +387,12 @@ class ConstantArray : public Constant {
   ///
   std::string getAsString() const;
 
+  /// getAsCString - If this array is isCString(), then this method converts the
+  /// array (without the trailing null byte) to an std::string and returns it.
+  /// Otherwise, it asserts out.
+  ///
+  std::string getAsCString() const;
+
   /// isNullValue - Return true if this is the value that would be returned by
   /// getNullValue.  This always returns false because zero arrays are always
   /// created as ConstantAggregateZero objects.

llvm/lib/VMCore/Constants.cpp

@@ -1011,17 +1011,32 @@ bool ConstantArray::isCString() const {
 }
 
 
-/// getAsString - If the sub-element type of this array is i8
-/// then this method converts the array to an std::string and returns it.
-/// Otherwise, it asserts out.
+/// convertToString - Helper function for getAsString() and getAsCString().
+static std::string convertToString(const User *U, unsigned len)
+{
+  std::string Result;
+  Result.reserve(len);
+  for (unsigned i = 0; i != len; ++i)
+    Result.push_back((char)cast<ConstantInt>(U->getOperand(i))->getZExtValue());
+  return Result;
+}
+
+/// getAsString - If this array is isString(), then this method converts the
+/// array to an std::string and returns it.  Otherwise, it asserts out.
 ///
 std::string ConstantArray::getAsString() const {
   assert(isString() && "Not a string!");
-  std::string Result;
-  Result.reserve(getNumOperands());
-  for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
-    Result.push_back((char)cast<ConstantInt>(getOperand(i))->getZExtValue());
-  return Result;
+  return convertToString(this, getNumOperands());
+}
+
+
+/// getAsCString - If this array is isCString(), then this method converts the
+/// array (without the trailing null byte) to an std::string and returns it.
+/// Otherwise, it asserts out.
+///
+std::string ConstantArray::getAsCString() const {
+  assert(isCString() && "Not a string!");
+  return convertToString(this, getNumOperands() - 1);
 }
 
 

llvm/tools/lto/LTOModule.cpp

@@ -191,7 +191,7 @@ bool LTOModule::objcClassNameFromExpression(Constant *c, std::string &name) {
       Constant *cn = gvn->getInitializer();
       if (ConstantArray *ca = dyn_cast<ConstantArray>(cn)) {
         if (ca->isCString()) {
-          name = ".objc_class_name_" + ca->getAsString();
+          name = ".objc_class_name_" + ca->getAsCString();
           return true;
         }
       }