code: def gf2mulmod(x, y, m):
      z = 0
      while x > 0:
          if (x & 1) != 0:
              z ^= y
          y <<= 1
          y2 = y ^ m
          if y2 < y:
              y = y2
          x >>= 1
      return z
  
label_desc: Use image node_id 1 for calling a global function with example usage: gf2mulmod(x, y, m) and returns: z