On Mon, Feb 27, 2006 at 09:46:42AM -0800, Chip Salzenberg wrote: > On Fri, Feb 24, 2006 at 12:57:24AM +0100, Leopold Toetsch wrote: > > On Feb 24, 2006, at 0:23, Patrick R. Michaud wrote: > > >>[...] > > >I've just committed an update (r11722) that eliminates PGE's > > >use of save/restore opcodes in the code it generates -- indeed, > > >PGE no longer has any save or restore opcodes and thus doesn't > > >need the user stack at all. > > > > That's indeed an (indirect) answer to the 'do we really need it' part ;) > > Is there any other client of the user stack that can't be easily replaced by > some kind of *Array? It'd be nice to lop off such a low-value feature.
As Will Coleda mentioned, the only real advantage of the user stack over an *Array seems to be that each subroutine wanting to manipulate the stack doesn't have to first look up a global symbol in order to do it. Intuitively, it would seem that a user stack, with its specialized parrot opcodes, ought to be significantly faster than simply using another array-ish object as a stack. It was this sort of (incorrect) thinking that led me to use it over an array in the first place. Since that is apparently not the case, I don't see any real use for keeping the user stack. (In PGE's case, using an array instead of the userstack is also superior for a number of other reasons, mostly having to do with being able to manipulate large parts of the stack in a single operation.) Pm
