Armin Rigo wrote:
Hi Antonio,
On Fri, Apr 14, 2006 at 04:53:28PM +0200, Antonio Cuni wrote:
# lltypesystem
def ll_listindex(lst, obj, eqfn):
items = lst.ll_items()
(...)
if items[j] == obj:
# ootypesystem
def ll_listindex(lst, obj, eqfn):
(...)
if lst.getitem_nonneg(j) == obj:
Another solution could be to add an extra level of indirection but I
guess this could bring to some efficiency penalty.
I think this is kind-of-reasonable. The ADT method approach of the
lltypesystem was introduced late during the development of the rtyper;
by now, it would be reasonable to define common method names between the
ADT methods of the lltypesystem and the GENERIC_METHODS of the
ootypesystem.
I am unsure about the performance penalty. The current version of many
ll helpers, for example, read the 'items' pointer only once and reuse
it; if this gets replaced by ADT methods like 'getitem_nonneg()', it
means that althought the call is probably inlined there is still the
overhead of reading 'items' through each iteration in the list. Who
knows, maybe C compilers will notice and move the read out of the loop.
Just give it a try on a small example like ll_listindex(), I guess...
A different comment: as you mentioned on IRC it would be nice if the
back-end could choose which methods it implements natively. At one
point there was the idea that maybe the 'oopspec' attributes that
started to show up in lltypesystem/rlist.py (used by the JIT only) could
be useful in this respect. If I remember correctly, the idea didn't
work out because of the different 'lowleveltype' needed,
yes, the problem was not re-using code as such, indeed it should not be hard
to write generic code that can be shared using adt methods etc.
The problem was trying to share the same type between ootype and lltype,
Instances are not Ptrs and don't even behave similarly enough, this is where
trying to reuse completely the lltypesystem rlist and rtuple code broke.
and the
difference in the interface. Merging the ADT method names of lltyped
lists and the GENERIC_METHODS of ootyped lists could be a step in this
direction again. The interesting point is that each oo back-end could
then choose to special-case the ll_xxx() functions with the oopspecs
that they recognize, and just translate the other ones normally. (The
ll back-ends always translate them all.)
A bientot,
Armin.
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