Re: Shrinking the C core

[Ihor Radchenko]

Eli Zaretskii <eliz@gnu.org> writes:

>>   CHECK_NUMBER (n);
>>   if (NILP (d))
>>     return FLOATP (n) ? double_to_integer (double_round (XFLOAT_DATA (n))) : 
>> n;
>> ...
>> During native compilation, if type information and n and d is available,
>> GCC might have a chance to cut a number of branches away from the above
>> code.
>
> Cut them how?  AFAICT, none of the tests above are redundant.

Consider the following:

(let ((a 10))
  (setq a (+ a 100))
  (floor a nil))

During compilation of the above code, the compiler will know that a is a
positive integer. Therefore, CHECK_NUMBER, NILP, and FLOATP are not
necessary and can be omitted in the call to `floor':

(let ((a 10))
 (setq a (+ a 100))
 a)

However, GCC JIT has no information about the internal structure of the
`floor' subr. Hence, it is currently unable to perform such
optimization.

It could, if it were somehow given an information about `floor'
implementation.

-- 
Ihor Radchenko // yantar92,
Org mode contributor,
Learn more about Org mode at <https://orgmode.org/>.
Support Org development at <https://liberapay.com/org-mode>,
or support my work at <https://liberapay.com/yantar92>