src/share/vm/opto/loopTransform.cpp

*** 707,720 ****
--- 707,723 ----
        stride_con < 0 && ((limit_type->_lo - stride_con) <= limit_type->_lo))
      return false;  // overflow
  
    // Adjust body_size to determine if we unroll or not
    uint body_size = _body.size();
+   // Key test to unroll loop in CRC32 java code
+   int xors_in_loop = 0;
    // Also count ModL, DivL and MulL which expand mightly
    for (uint k = 0; k < _body.size(); k++) {
      Node* n = _body.at(k);
      switch (n->Opcode()) {
+       case Op_XorI: xors_in_loop++; break; // CRC32 java code
        case Op_ModL: body_size += 30; break;
        case Op_DivL: body_size += 30; break;
        case Op_MulL: body_size += 10; break;
        case Op_StrComp:
        case Op_StrEquals:
*** 727,736 ****
--- 730,740 ----
      } // switch
    }
  
    // Check for being too big
    if (body_size > (uint)LoopUnrollLimit) {
+     if (xors_in_loop >= 4 && body_size < (uint)LoopUnrollLimit*4) return true;
      // Normal case: loop too big
      return false;
    }
  
    // Unroll once!  (Each trip will soon do double iterations)