if (VM.VerifyAssertions) VM.assert(available > 0);
if (VM.VerifyAssertions) VM._assert(available > 0);
  public void minorEnd() throws VM_PragmaUninterruptible {      VM_Address middle = VM_Memory.roundDownPage(start.add(end.diff(start) / 2));      if (nurseryHeap.sense() == VM_ContiguousHeap.FORWARD) {	  int available = fromHeap.current().diff(middle);	  if (VM.VerifyAssertions) VM.assert(available > 0);	  VM_Address newMiddle = nurseryHeap.start.add(available);	  nurseryHeap.setRegion(nurseryHeap.start, newMiddle, VM_ContiguousHeap.FORWARD);	  fromHeap.extendRegion(newMiddle);      }      else {	  int available = middle.diff(fromHeap.current());	  if (VM.VerifyAssertions) VM.assert(available > 0);	  VM_Address newMiddle = nurseryHeap.end.sub(available);	  nurseryHeap.setRegion(newMiddle, nurseryHeap.end, VM_ContiguousHeap.BACKWARD);	  fromHeap.extendRegion(newMiddle);      }  }