Around line 177 we have:

LIR_Opr tmp = new_pointer_register();
      if (Assembler::operand_valid_for_add_sub_immediate(large_disp)) {
        __ add(tmp, tmp, LIR_OprFact::intptrConst(large_disp)); <---
        index = tmp;
      } else {

This is supposed to be calculating "tmp = index + large_disp" but it actually does "large_disp = tmp + tmp".

On line 157 if index is a constant we add it to large_disp and set index to LIR_OprFact::illegalOpr. Then on line 194:

  // at this point we either have base + index or base + displacement
  if (large_disp == 0) {
    return new LIR_Address(base, index, type); <----
  } else {

If the displacement and constant index sum to zero we end up passing an illegal value into LIR_Address, triggering an assert.