Piers Cawley <[EMAIL PROTECTED]> wrote: > Leopold Toetsch <[EMAIL PROTECTED]> writes:
>> Matt Fowles <[EMAIL PROTECTED]> wrote: >> >>> Thanks for the clear explanation. I did not realize that S registers >>> could switch pointers, that does make things a little harder. I have >>> a recommendation for a possible hybrid solution. Incur the cost of >>> spilling I,S,N registers heavily. Restore the state of P register. >> >> My conclusion was that with the copying approach I,S,N registers are >> unusable. > But you only need to copy when the frame you're restoring is a full > continuation Yes. With the effect that semantics of I,S,N (i.e. value registers) suddenly changes. > I'd submit that, in the vast majority of cases you're not going to be > dealing with full continuations, and on the occasions when you are the > programmer using them will be aware of the cost and will be willing to > pay it. *If* the programmer is aware of the fact that a subroutine can return multiple times, he can annotate the source so that a correct CFG is created that prevents register reusing alltogether. The problem is gone in the first place. *If* that's not true, you'd get the effect that suddenly I,S,N registers restore to some older values which makes this registers de facto unusable. leo
