C++ StackValue类代码示例

void interpretedVFrame::set_locals(StackValueCollection* values) const {
  if (values == NULL || values->size() == 0) return;

  int length = method()->max_locals();
  if (method()->is_native()) {
    // If the method is native, max_locals is not telling the truth.
    // maxlocals then equals the size of parameters
    length = method()->size_of_parameters();
  }

  assert(length == values->size(), "Mismatch between actual stack format and supplied data");

  // handle locals
  for (int i = 0; i < length; i++) {
    // Find stack location
    intptr_t *addr = locals_addr_at(i);

    // Depending on oop/int put it in the right package
    StackValue *sv = values->at(i);
    assert(sv != NULL, "sanity check");
    if (sv->type() == T_OBJECT) {
      *(oop *) addr = (sv->get_obj())();
    } else {                   // integer
      *addr = sv->get_int();
    }
  }
}

void
FrameInfo::popRegsAndSync(uint32_t uses)
{
    // x86 has only 3 Value registers. Only support 2 regs here for now,
    // so that there's always a scratch Value register for reg -> reg
    // moves.
    JS_ASSERT(uses > 0);
    JS_ASSERT(uses <= 2);
    JS_ASSERT(uses <= stackDepth());

    syncStack(uses);

    switch (uses) {
      case 1:
        popValue(R0);
        break;
      case 2: {
        // If the second value is in R1, move it to R2 so that it's not
        // clobbered by the first popValue.
        StackValue *val = peek(-2);
        if (val->kind() == StackValue::Register && val->reg() == R1) {
            masm.moveValue(R1, R2);
            val->setRegister(R2);
        }
        popValue(R1);
        popValue(R0);
        break;
      }
      default:
        MOZ_ASSUME_UNREACHABLE("Invalid uses");
    }
}

void javaVFrame::print_lock_info(int frame_count) {        
  ResourceMark rm;

  // If this is the first frame, and java.lang.Object.wait(...) then print out the receiver.
  if (frame_count == 0 && method()->name() == vmSymbols::wait_name() && 
      instanceKlass::cast(method()->method_holder())->name() == vmSymbols::java_lang_Object()) {
    StackValueCollection* locs = locals();      
    if (!locs->is_empty()) {
      StackValue* sv = locs->at(0);
      if (sv->type() == T_OBJECT) {
        Handle o = locs->at(0)->get_obj();    
        if (o.not_null()) {
          instanceKlass* ik = instanceKlass::cast(o->klass());
          tty->print_cr("\t- waiting on <" INTPTR_FORMAT "> (a %s)", o(), ik->external_name());
        }
      }
    }        
  }    
  
  // Print out all monitors that we have locked or are trying to lock
  GrowableArray<MonitorInfo*>* mons = monitors();
  if (!mons->is_empty()) {
    bool found_first_monitor = false;
    for (int index = (mons->length()-1); index >= 0; index--) {
      MonitorInfo* monitor = mons->at(index);
      if (monitor->owner() != NULL) {
        //
        // First, assume we have the monitor locked. If we haven't found an
        // owned monitor before and this is the first frame, then we need to
        // see if the thread is blocked.
        //
        const char *lock_state = "locked"; // assume we have the monitor locked
        if (!found_first_monitor && frame_count == 0) {
          switch (thread()->thread_state()) {
          case _thread_blocked:
          case _thread_blocked_trans:
            lock_state = "waiting to lock";
            break;
          }
        }
        found_first_monitor = true;
        instanceKlass* ik = instanceKlass::cast(monitor->owner()->klass());
        tty->print_cr("\t- %s <" INTPTR_FORMAT "> (a %s)", lock_state, monitor->owner(), ik->external_name());
      }
    }  
  }
}

void
FrameInfo::popValue(ValueOperand dest)
{
    StackValue *val = peek(-1);

    switch (val->kind()) {
      case StackValue::Constant:
        masm.moveValue(val->constant(), dest);
        break;
      case StackValue::LocalSlot:
        masm.loadValue(addressOfLocal(val->localSlot()), dest);
        break;
      case StackValue::ArgSlot:
        masm.loadValue(addressOfArg(val->argSlot()), dest);
        break;
      case StackValue::ThisSlot:
        masm.loadValue(addressOfThis(), dest);
        break;
      case StackValue::Stack:
        masm.popValue(dest);
        break;
      case StackValue::Register:
        masm.moveValue(val->reg(), dest);
        break;
      default:
        MOZ_ASSUME_UNREACHABLE("Invalid kind");
    }

    // masm.popValue already adjusted the stack pointer, don't do it twice.
    pop(DontAdjustStack);
}

void interpretedVFrame::set_locals(StackValueCollection* values) const {
  if (values == NULL || values->size() == 0) return;

  int length = method()->max_locals();
  if (method()->is_native()) {
    // If the method is native, max_locals is not telling the truth.
    // maxlocals then equals the size of parameters 
    length = method()->size_of_parameters();
  }

  assert(length == values->size(), "Mismatch between actual stack format and supplied data");

  // Get oopmap describing oops and int for current bci
  InterpreterOopMap oop_mask;
  if (TraceDeoptimization && Verbose) {
    methodHandle m_h(thread(), method());
    OopMapCache::compute_one_oop_map(m_h, bci(), &oop_mask);
  } else {
    method()->mask_for(bci(), &oop_mask);
  }

  // handle locals
  for (int i = 0; i < length; i++) {
    // Find stack location
    intptr_t *addr = locals_addr_at(i); 

    // Depending on oop/int put it in the right package
    StackValue *sv = values->at(i);
    assert(sv != NULL, "sanity check");
    if (oop_mask.is_oop(i)) { // oop value
      *(oop *) addr = (sv->get_obj())();
    } else {                   // integer
      *addr = sv->get_int();
    }
  }
}

void vframeArrayElement::fill_in(compiledVFrame* vf) {

// Copy the information from the compiled vframe to the
// interpreter frame we will be creating to replace vf

  _method = vf->method();
  _bci    = vf->raw_bci();
  _reexecute = vf->should_reexecute();

  int index;

  // Get the monitors off-stack

  GrowableArray<MonitorInfo*>* list = vf->monitors();
  if (list->is_empty()) {
    _monitors = NULL;
  } else {

    // Allocate monitor chunk
    _monitors = new MonitorChunk(list->length());
    vf->thread()->add_monitor_chunk(_monitors);

    // Migrate the BasicLocks from the stack to the monitor chunk
    for (index = 0; index < list->length(); index++) {
      MonitorInfo* monitor = list->at(index);
      assert(!monitor->owner_is_scalar_replaced(), "object should be reallocated already");
      assert(monitor->owner() == NULL || (!monitor->owner()->is_unlocked() && !monitor->owner()->has_bias_pattern()), "object must be null or locked, and unbiased");
      BasicObjectLock* dest = _monitors->at(index);
      dest->set_obj(monitor->owner());
      monitor->lock()->move_to(monitor->owner(), dest->lock());
    }
  }

  // Convert the vframe locals and expressions to off stack
  // values. Because we will not gc all oops can be converted to
  // intptr_t (i.e. a stack slot) and we are fine. This is
  // good since we are inside a HandleMark and the oops in our
  // collection would go away between packing them here and
  // unpacking them in unpack_on_stack.

  // First the locals go off-stack

  // FIXME this seems silly it creates a StackValueCollection
  // in order to get the size to then copy them and
  // convert the types to intptr_t size slots. Seems like it
  // could do it in place... Still uses less memory than the
  // old way though

  StackValueCollection *locs = vf->locals();
  _locals = new StackValueCollection(locs->size());
  for(index = 0; index < locs->size(); index++) {
    StackValue* value = locs->at(index);
    switch(value->type()) {
      case T_OBJECT:
        assert(!value->obj_is_scalar_replaced(), "object should be reallocated already");
        // preserve object type
        _locals->add( new StackValue((intptr_t) (value->get_obj()()), T_OBJECT ));
        break;
      case T_CONFLICT:
        // A dead local.  Will be initialized to null/zero.
        _locals->add( new StackValue());
        break;
      case T_INT:
        _locals->add( new StackValue(value->get_int()));
        break;
      default:
        ShouldNotReachHere();
    }
  }

  // Now the expressions off-stack
  // Same silliness as above

  StackValueCollection *exprs = vf->expressions();
  _expressions = new StackValueCollection(exprs->size());
  for(index = 0; index < exprs->size(); index++) {
    StackValue* value = exprs->at(index);
    switch(value->type()) {
      case T_OBJECT:
        assert(!value->obj_is_scalar_replaced(), "object should be reallocated already");
        // preserve object type
        _expressions->add( new StackValue((intptr_t) (value->get_obj()()), T_OBJECT ));
        break;
      case T_CONFLICT:
        // A dead stack element.  Will be initialized to null/zero.
        // This can occur when the compiler emits a state in which stack
        // elements are known to be dead (because of an imminent exception).
        _expressions->add( new StackValue());
        break;
      case T_INT:
        _expressions->add( new StackValue(value->get_int()));
        break;
      default:
        ShouldNotReachHere();
    }
  }
}

//.........这里部分代码省略.........

  _frame.patch_pc(thread, pc);

  assert (!method()->is_synchronized() || locks > 0, "synchronized methods must have monitors");

  BasicObjectLock* top = iframe()->interpreter_frame_monitor_begin();
  for (int index = 0; index < locks; index++) {
    top = iframe()->previous_monitor_in_interpreter_frame(top);
    BasicObjectLock* src = _monitors->at(index);
    top->set_obj(src->obj());
    src->lock()->move_to(src->obj(), top->lock());
  }
  if (ProfileInterpreter) {
    iframe()->interpreter_frame_set_mdx(0); // clear out the mdp.
  }
  iframe()->interpreter_frame_set_bcx((intptr_t)bcp); // cannot use bcp because frame is not initialized yet
  if (ProfileInterpreter) {
    methodDataOop mdo = method()->method_data();
    if (mdo != NULL) {
      int bci = iframe()->interpreter_frame_bci();
      if (use_next_mdp) ++bci;
      address mdp = mdo->bci_to_dp(bci);
      iframe()->interpreter_frame_set_mdp(mdp);
    }
  }

  // Unpack expression stack
  // If this is an intermediate frame (i.e. not top frame) then this
  // only unpacks the part of the expression stack not used by callee
  // as parameters. The callee parameters are unpacked as part of the
  // callee locals.
  int i;
  for(i = 0; i < expressions()->size(); i++) {
    StackValue *value = expressions()->at(i);
    intptr_t*   addr  = iframe()->interpreter_frame_expression_stack_at(i);
    switch(value->type()) {
      case T_INT:
        *addr = value->get_int();
        break;
      case T_OBJECT:
        *addr = value->get_int(T_OBJECT);
        break;
      case T_CONFLICT:
        // A dead stack slot.  Initialize to null in case it is an oop.
        *addr = NULL_WORD;
        break;
      default:
        ShouldNotReachHere();
    }
  }


  // Unpack the locals
  for(i = 0; i < locals()->size(); i++) {
    StackValue *value = locals()->at(i);
    intptr_t* addr  = iframe()->interpreter_frame_local_at(i);
    switch(value->type()) {
      case T_INT:
        *addr = value->get_int();
        break;
      case T_OBJECT:
        *addr = value->get_int(T_OBJECT);
        break;
      case T_CONFLICT:
        // A dead location. If it is an oop then we need a NULL to prevent GC from following it
        *addr = NULL_WORD;