C++ Convert::value方法代码示例

static bool match(UnsafeRawOp* x,
                  Instruction** base,
                  Instruction** index,
                  int*          log2_scale) {
  Instruction* instr_to_unpin = NULL;
  ArithmeticOp* root = x->base()->as_ArithmeticOp();
  if (root == NULL) return false;
  // Limit ourselves to addition for now
  if (root->op() != Bytecodes::_ladd) return false;
  // Try to find shift or scale op
  if (match_index_and_scale(root->y(), index, log2_scale, &instr_to_unpin)) {
    *base = root->x();
  } else if (match_index_and_scale(root->x(), index, log2_scale, &instr_to_unpin)) {
    *base = root->y();
  } else if (root->y()->as_Convert() != NULL) {
    Convert* convert = root->y()->as_Convert();
    if (convert->op() == Bytecodes::_i2l && convert->value()->type() == intType) {
      // pick base and index, setting scale at 1
      *base  = root->x();
      *index = convert->value();
      *log2_scale = 0;
    } else {
      return false;
    }
  } else {
    // doesn't match any expected sequences
    return false;
  }
  // Typically the addition is pinned, as it is the result of an
  // inlined routine. We want to unpin it so as to avoid the long
  // addition, but in order to do so we must still ensure that the
  // operands are pinned, as they may be computed arbitrarily before
  // the Unsafe op completes (even if the Unsafe op is pinned). At
  // this point we do not really need to pin Unsafe raw or object
  // gets.
  if (root->is_pinned()) {
    if (root->pin_state() == Instruction::PinInlineReturnValue) {
      assert(x->is_pinned(), "All unsafe raw ops should be pinned");
      root->unpin(Instruction::PinInlineReturnValue);
      (*base)->pin();
      (*index)->pin();
    } else {
      // can't safely unpin this instruction
      return false;
    }
  }

  if (PrintUnsafeOptimization && instr_to_unpin != NULL) {
    tty->print_cr("pin_state = 0x%x", instr_to_unpin->pin_state());
    instr_to_unpin->print();
  }
  return true;
}

void Canonicalizer::do_StoreField     (StoreField*      x) {
  // If a value is going to be stored into a field or array some of
  // the conversions emitted by javac are unneeded because the fields
  // are packed to their natural size.
  Convert* conv = x->value()->as_Convert();
  if (conv) {
    Value value = NULL;
    BasicType type = x->field()->type()->basic_type();
    switch (conv->op()) {
    case Bytecodes::_i2b: if (type == T_BYTE)  value = conv->value(); break;
    case Bytecodes::_i2s: if (type == T_SHORT || type == T_BYTE) value = conv->value(); break;
    case Bytecodes::_i2c: if (type == T_CHAR  || type == T_BYTE)  value = conv->value(); break;
    }
    // limit this optimization to current block
    if (value != NULL && in_current_block(conv)) {
      set_canonical(new StoreField(x->obj(), x->offset(), x->field(), value, x->is_static(),
                                   x->state_before(), x->needs_patching()));
      return;
    }
  }

}

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;
}