{
RegisterSet allRegs= new RegisterSet();
for (OnePathInstructionRegisterContents curInst : c.path)
{
InstructionUseInfo useInfo= beenTo.get(curInst.instruction).useInfo;
allRegs.orEq(useInfo.allWrites());
allRegs.orEq(useInfo.usedReg());
}
// Look for a retain, no writes, then a release, and then get
// rid of the symmetric retain / release