> What about liveness? No hard reg, pseudo, mem will live avross the > unspec volatile. Right?
Wrong. A volatile unspec may use/change machine state not directly accessible by gcc. Any use of or changes to the machine state modelled by gcc should be explicit in the pattern. i.e. if your pattern clobbers a hard register, you should include a clobber of that register in parallel with the unspec. Likewise if you set a hard register to a useful value, you should include an explicit set, typically something like "(set (reg) (unspec_volatile ...))" Paul
