On Tue, 26 Aug 2008, luben wrote:
I have noticed that Rakudo (and NQP) generates different PIR code for
implicit and explicit returns.
Example for implicit return:
sub foo($n){
$n;
}
And example for explicit return:
sub foo($n){
return $n;
}
Is this on purpose? The implicit return is 4-5 times faster than explicit
return.
the implicit return is by definition always at the end of a sub and
therefore emits a PIR .return(). it's fast and easy.
the explicit return, in contrast, could be anywhere in a subroutine,
including loops, closures, etc. these constructs are also implemented
using parrot subs, so using .return() would return control to the
sub that *contains* the loop, closure, or whatever construct you're using.
that's not what we want.
to get around this, an exception is thrown and caught by the sub that
*should* do the actual returning. you can see that in the PIR you
generate.
(pmichaud, i hope i explained this right! ;-)
-jeff
