if (VM.VerifyAssertions) VM._assert(!SimpleRCHeader.isGreen(obj));
if (VM.VerifyAssertions) VM._assert(!SimpleRCBaseHeader.isGreen(obj));
  private final void doScanPhase() {    VM_Address obj;    AddressQueue src = (cycleBufferAisOpen) ? cycleBufferA : cycleBufferB;    AddressQueue tgt = (cycleBufferAisOpen) ? cycleBufferB : cycleBufferA;    rcCollector.scanPhase();    while (!(obj = src.pop()).isZero()) {      if (VM.VerifyAssertions) VM._assert(!SimpleRCHeader.isGreen(obj));      rcCollector.scan(obj);      tgt.push(obj);    }    cycleBufferAisOpen = !cycleBufferAisOpen;  }