Robert Bradshaw wrote:
> On Mon, 4 Aug 2008, Dag Sverre Seljebotn wrote:
>
>> Stefan Behnel wrote:
>>> Dag Sverre Seljebotn wrote:
>>>> If we make positive int literals unsigned long rather than plain long,
>>>> constant-index buffer lookups are going to be optimized for free. Is
>>>> there going to be any ill side-effects from doing this?
>>>>
>>>> (If not, I can always special-case int literals used for buffer lookups.)
>>> What about enabling this, adding a test module dedicated to integer
>>> literals, casting and arithmetic, and running the (complete) test suite
>>> with
>>>
>>> -Wall -pedantic
>>>
>>> ?
>> Sure, but that would have been a lot of work only to get a reply here
>> afterwards that "this whole idea would obviously not work because X"
>> from people who know the code base better :-)
>
> I think in general that is a good idea, but the problem is that
> PyLong_FromUnsignedLong is slower than PyInt_FromLong and produces python
> longs rather than python ints. One would need a special type (or flag) to
> indicate that the top bit can be assumed to be 0.
And there's my X.
Do you see any weaknesses in this? (as a general, somewhat orthogonal
runtime optimization ... the hit should be negligible compared to
PyInt_FromUnsignedLong, or...?):
static INLINE PyObject* __Pyx_ObjectFromUnsignedLong(unsigned long value) {
if (top bit of value is 0) return PyInt_FromLong((long)value);
else return PyLong_FromUnsignedLong(value);
}
--
Dag Sverre
_______________________________________________
Cython-dev mailing list
[email protected]
http://codespeak.net/mailman/listinfo/cython-dev
