Hi Lang, > + // Record PHI def. > + //assert(!hasPHIDef(DestReg) && "Vreg has multiple phi-defs?"); > + //PHIDefs[DestReg] = &MBB; this doesn't do much. > + // Record the kill. > + //PHIKills[SrcReg].insert(&opBlock); Neither does this :) Ciao, Duncan.