Add useful helpers to AddrSpaceCastInst

[silvas]

Could you just add these as needed when refactoring? Adding these helpers seems like a no-brainer once the code needs them.

[arsenm]

I usually prefer to add things like this separately from their uses

[arsenm]

r267450

include/llvm/IR/Instructions.h

   static inline bool classof(const Value *V) {
     return isa<Instruction>(V) && classof(cast<Instruction>(V));
   }
+
+  /// \brief Gets the pointer operand.
+  Value *getPointerOperand() {
+    return getOperand(0);
+  }
+
+  /// \brief Gets the pointer operand.
+  const Value *getPointerOperand() const {
+    return getOperand(0);
+  }
+
+  /// \brief Gets the operand index of the pointer operand.
+  static unsigned getPointerOperandIndex() {
+    return 0U;
+  }
+
+  /// \brief Returns the address space of the pointer operand.
+  unsigned getSrcAddressSpace() const {
+    return getPointerOperand()->getType()->getPointerAddressSpace();
+  }
+
+  /// \brief Returns the address space of the result.
+  unsigned getDestAddressSpace() const {
+    return getType()->getPointerAddressSpace();
+  }
 };
 
 } // End llvm namespace