add missing operator

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35613 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/ADT/APInt.h

@@ -543,6 +543,10 @@ public:
     return (*this) - APInt(BitWidth, RHS);
   }
   
+  APInt operator<<(unsigned Bits) const {
+    return shl(Bits);
+  }
+
   /// Arithmetic right-shift this APInt by shiftAmt.
   /// @brief Arithmetic right-shift function.
   APInt ashr(uint32_t shiftAmt) const;