C++ Constant::type方法代码示例

void Canonicalizer::do_ArrayLength    (ArrayLength*     x) {
  NewArray* array = x->array()->as_NewArray();
  if (array != NULL && array->length() != NULL) {
    Constant* length = array->length()->as_Constant();
    if (length != NULL) {
      // do not use the Constant itself, but create a new Constant
      // with same value Otherwise a Constant is live over multiple
      // blocks without being registered in a state array.
      assert(length->type()->as_IntConstant() != NULL, "array length must be integer");
      set_constant(length->type()->as_IntConstant()->value());
    }
  } else {
    LoadField* lf = x->array()->as_LoadField();
    if (lf != NULL) {
      ciField* field = lf->field();
      if (field->is_constant() && field->is_static()) {
        // final static field
        ciObject* c = field->constant_value().as_object();
        if (c->is_array()) {
          ciArray* array = (ciArray*) c;
          set_constant(array->length());
        }
      }
    }
  }
}

void Canonicalizer::do_ArrayLength    (ArrayLength*     x) {
  NewArray*  na;
  Constant*  ct;
  LoadField* lf;

  if ((na = x->array()->as_NewArray()) != NULL) {
    // New arrays might have the known length.
    // Do not use the Constant itself, but create a new Constant
    // with same value Otherwise a Constant is live over multiple
    // blocks without being registered in a state array.
    Constant* length;
    if (na->length() != NULL &&
        (length = na->length()->as_Constant()) != NULL) {
      assert(length->type()->as_IntConstant() != NULL, "array length must be integer");
      set_constant(length->type()->as_IntConstant()->value());
    }

  } else if ((ct = x->array()->as_Constant()) != NULL) {
    // Constant arrays have constant lengths.
    ArrayConstant* cnst = ct->type()->as_ArrayConstant();
    if (cnst != NULL) {
      set_constant(cnst->value()->length());
    }

  } else if ((lf = x->array()->as_LoadField()) != NULL) {
    ciField* field = lf->field();
    if (field->is_static_constant()) {
      assert(PatchALot || ScavengeRootsInCode < 2, "Constant field loads are folded during parsing");
      ciObject* c = field->constant_value().as_object();
      if (!c->is_null_object()) {
        set_constant(c->as_array()->length());
      }
    }
  }
}

// perform constant and interval tests on index value
bool AccessIndexed::compute_needs_range_check() {
  Constant* clength = length()->as_Constant();
  Constant* cindex = index()->as_Constant();
  if (clength && cindex) {
    IntConstant* l = clength->type()->as_IntConstant();
    IntConstant* i = cindex->type()->as_IntConstant();
    if (l && i && i->value() < l->value() && i->value() >= 0) {
      return false;
    }
  }
  return true;
}

static bool match_index_and_scale(Instruction*  instr,
                                  Instruction** index,
                                  int*          log2_scale,
                                  Instruction** instr_to_unpin) {
  *instr_to_unpin = NULL;

  // Skip conversion ops
  Convert* convert = instr->as_Convert();
  if (convert != NULL) {
    instr = convert->value();
  }

  ShiftOp* shift = instr->as_ShiftOp();
  if (shift != NULL) {
    if (shift->is_pinned()) {
      *instr_to_unpin = shift;
    }
    // Constant shift value?
    Constant* con = shift->y()->as_Constant();
    if (con == NULL) return false;
    // Well-known type and value?
    IntConstant* val = con->type()->as_IntConstant();
    if (val == NULL) return false;
    if (shift->x()->type() != intType) return false;
    *index = shift->x();
    int tmp_scale = val->value();
    if (tmp_scale >= 0 && tmp_scale < 4) {
      *log2_scale = tmp_scale;
      return true;
    } else {
      return false;
    }
  }

  ArithmeticOp* arith = instr->as_ArithmeticOp();
  if (arith != NULL) {
    if (arith->is_pinned()) {
      *instr_to_unpin = arith;
    }
    // Check for integer multiply
    if (arith->op() == Bytecodes::_imul) {
      // See if either arg is a known constant
      Constant* con = arith->x()->as_Constant();
      if (con != NULL) {
        *index = arith->y();
      } else {
        con = arith->y()->as_Constant();
        if (con == NULL) return false;
        *index = arith->x();
      }
      if ((*index)->type() != intType) return false;
      // Well-known type and value?
      IntConstant* val = con->type()->as_IntConstant();
      if (val == NULL) return false;
      switch (val->value()) {
      case 1: *log2_scale = 0; return true;
      case 2: *log2_scale = 1; return true;
      case 4: *log2_scale = 2; return true;
      case 8: *log2_scale = 3; return true;
      default:            return false;
      }
    }
  }

  // Unknown instruction sequence; don't touch it
  return false;
}