Roman Zippel wrote: > Hi, > > On Wed, 20 Jun 2007, Kenneth Zadeck wrote: > > >> If we add the dead note there we are asserting that the value is >> modified by the caller. however it might not be and someone could write >> a piece of asm right after the call to use that reg if the person knew >> that the reg was not modified by that particular call. >> > > I have big problems to see this as a valid example, this sounds just > broken. First off the user had to know the register was alive before and > then the user had to magically know the register isn't clobbered by the > call (e.g. loading the address of the function into that register). > You could declare the variable as asm register variable, then it might > work, but then the register wouldn't be available for allocation anyway > and the whole problem changes. > > >> having the dead note there is asserting to the register allocator that >> they are free to use that reg after the calll in any way that it wants >> and there is a (small) possibility that is wrong. >> > > IMO there is nothing wrong with this. > > bye, Roman > The whole reason for bugzilla is to remind compiler developers that rare case cannot be ignored.
kenny
