[Python-Dev] Optimization targets - refcount

[Jeff Epler]

Maybe something like this:

#ifdef __GCC__
#define constant_p(x) __builtin_constant_p(x)
#else
#define constant_p(x) 0
#endif

#define Py_INCREF(x) \
    if( ! constant_p(x) || (x != Py_None && x != other immortals)) \
        actual Py_INCREF body(x)

this should allow the compiler, by constant propagation, to skip actual
Py_INCREF body when it sees
    Py_INCREF(Py_None)
and when it's
    Py_INCREF(nonconstant)
to have no test for equality with the immortal values.

does this actually work?  I didn't check.  I think that on some
important systems there may be no equivalent to gcc's
__builtin_constant_p(), and that Py_None is not a compile-time constant
(*cough* DLLs *cough*)

Jeff