{
last= curInst;
act= beenTo.get(curInst.instruction);
needsNull.orEq(act.useInfo.willNull);
act.useInfo.willNull= RegisterSet.none();
needsNull.andEqNot(act.useInfo.allWrites());
}
if (act != null)
{
if (last.instruction.getName().startsWith("return"))
{