* Andi Kleen ([email protected]) wrote:
> Mathieu Desnoyers <[email protected]> writes:
> > }
> > - profile_hit(SCHED_PROFILING, __builtin_return_address(0));
> > + cond_call(profile_on,
> > + profile_hit(SCHED_PROFILING, __builtin_return_address(0)));
>
> Would it be possible to use a syntax like
>
> if (unlikely_cond_call(variable)) { (or better name)
> ...
> }
>
> instead? I think that would be much nicer to read than having
> code in a macro argument
>
I see your point, but there is a level of control on the branch I would
lack by doing so: the ability to put the call in either the if or else
branch. It is an optimization on i386.
I could do it by defining my home-made if() :
cond_if (cond_call_name) {
code
}
The macro cond_if could then expand (this is a simplified example) in either in
if (cond)
or
if (cond)
else
Also, I live in the expectation that, someday, the gcc guys will be nice
enough to add some kind of support for a nop-based jump that would
require code patching to put a jump instead. If it ever happens, my
macro could evolve into this for newer compiler versions, which I could
not do with the if() statement you are proposing.
--
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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