Jason Gloudon wrote:
On Tue, Oct 29, 2002 at 02:40:14PM +0100, Leopold Toetsch wrote:+ cur_var_ptr = (size_t)((ptrdiff_t)cur_var_ptr + PARROT_PTR_ALIGNMENT)When PARROT_PTR_ALIGNMENT is not 1, that much pointers -1 are skipped during stack scanning by incrementing cur_var_ptr by sizeof(size_t) * PARROT_PTR_ALIGNMENT bytes.
ptrdiff_t is not a pointer type, so cur_var_ptr + PARROT_PTR_ALIGNMENT skips exactly PARROT_PTR_ALIGNMENT bytes. You may not be matching ( )'s quite right.
Brr, yes. I checked with gdb. cur_var_ptr is incremented by PARROT_PTR_ALIGNMENT _bytes_ i.e. by 1 byte on i386. Can we really have e.g. odd aligned PMCs on stack? I don't think so. Or am I still missing something?
As a side note: applying your patch slows down e.g. life.pasm by ~2%. (I really don't see why).
Are you compiling with optimization enabled ? Is the difference consistent ?
W/o optimization, but consistent.
If the answer to both questions is yes, it is probably a cache effect related to the new variable on the function stack. I doubt the slowdown is universal. I will try to check on SPARC sometime today.
leo
