Armin Rigo wrote:
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...
Well,
as we decided on #pypy I've changed the ADT interface. As I wrote in the
commit log:
"""
The interface of ListRepr and FixedSizeListRepr has changed: two
accessor methods has been added: ll_getitem_fast and
ll_setitem_fast. They should be used instead of the ll_items()[index]
idiom: that way when ootypesystem's list will support that interface
we will able to write function useable with both typesystem with no
modification.
The various ll_* helper function has been adapted to use the new
interface. Moreover function that accessed directly to the "l.length"
field has been changed to call the "ll_length()" method instead, for
the same reasons as above.
"""
The next step is to rename ootypesystem's list _GENERIC_METHODS to match
the ADT methods in lltypesystem's list, then we could try to share most
of ll_* function that currently belongs only to lltypesystem/rlist.py.
I hope I will do it tomorrow.
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, 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.)
I saw that 'oopspec' attributes, but I didn't understand the exact
semantic; your proposal sounds reasonable to me: if I can figure out
correctly this way the typesystem specific code would be reduced to the
minimum and will help to port other Repr such as rdict to ootypesystem,
too. I'll investigate a bit in this direction as soon as I can.
good Easter to all,
ciao Anto
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