code: function A(iid, base, offset, op, flags) {
          var bFlags = decodeBitPattern(flags, 1); // [isComputed]
          // avoid iid collision: make sure that iid+2 has the same source map as iid (@todo)
          var oprnd1 = G(iid+2, base, offset, createBitPattern(bFlags[0], true, false));
          return function (oprnd2) {
              // still possible to get iid collision with a mem operation
              var val = B(iid, op, oprnd1, oprnd2, createBitPattern(false, true, false));
              return P(iid, base, offset, val, createBitPattern(bFlags[0], true));
          };
      }
docs: Modify and assign +=, -= ...