anto.cuni at gmail.com
Tue May 2 12:01:27 CEST 2006
Sanghyeon Seo wrote:
> Is there some documentation on oopspec attribute? How one may use it
> in the backend?
I think there are no docs about the oopspec attribute. Armin wrote these
lines some time ago to respond to the same question:
The oopspec string tells what is the "abstract" list operation that this
particular ll_*() function implement. For example:
def ll_prepend(l, newitem):
ll_prepend.oopspec = 'list.insert(l, 0, newitem)'
means that ll_prepend() is equivalent to an insert with the index set to
zero. In the stirng, the pseudo-arguments between the ( ) are either
real argument names of the ll_ function, or constants.
So for example, if a backend has got its own way to implement the
insert() calls in general, it could figure out from the oopspec that the
ll_prepend() helper can be replaced by a custom stub invoking the
backend's own version of insertion with an index of 0. That's
essentially what the JIT does -- see handle_highlevel_operation() in
The CLI backend uses the oopspec attribute for replacing calls to
selected low-level helpers with native builtin methods; the code is
still very experimental since it doesn't parse the argument line: it
simply forwards the call using the first parameter as the target object
and subsequent parameters as method's arguments. By now the only
recognized oopspec is 'list.append' (i.e., ll_append) that is translated
to the 'Add' method.
If you want to look at my code see translator/cli/oopspec.py and the
_Call.render method in translator/cli/metavm.py; at the moment I put
these files in the cli/ directory, but they are general enough to be
shared among multiple backends (metavm would be useful only for backends
emitting bytecode, so not for gencl nor gensqueak, I guess).
The rationale behind this is that this way a backend can quickly gain
full list support by simply supply basic operations such as
ll_getitem_fast & Co; then each backend can choose what operation to
optimize based on their knowledge of the target system.
Btw, I have a doubt about oopspec, too: Armin told that the 'oopspec'
specifies the "abstract" operation that each ll_* helper implements;
does this abstract operation have to be one of standard list methods or
can I add new operations? I was thinking to add a 'll_remove_range' or
similar to be used by other helpers such as delslice and company; this
way backends can replace ll_remove_range with their
almost-surely-present equivalent without having to care about
python-specific logic such as slices or so.
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