It is interesting and very clear patch.
Probably you idea can be extended to support regular globals too. I mean
$GLOBALS["name"].
>
GLOBALS is itself in the auto global registry, so these would
automatically get picked up too. Oh, no, you probably mean have that
entire expression boil down to a CV, ah... that'll be slightly tricker
(since it'll involve rewriting the opcode), but in principle it
shouldn't be impossible. Even if it's ugly to do in the single-pass
compiler, an opcode optimizer could certainly handle it in its second
pass once the fetch_type is added to CV definitions...
BTW I am not sure this patch will give significant speedup, because locals
are used most often then globals, and your patch adds small overhead for
them.
Did you benchmarked your patch?
Well, I gave it the usual BogoMIPS treatment (Bogus Meaningless
Indication of Processor Speed for anyone who doesn't recognize that),
and I got the following encouraging numbers:
<?php
$_POST['foo'] = 'bar';
for($i = 0; $i<1000000; $i++)
$b = $_POST['foo'];
?>
[current -- without patch]
$ time sapi/cli/php -f test.php
real 0m1.057s
user 0m0.660s
sys 0m0.000s
[with patch]
$ time sapi/cli/php -f test.php
real 0m0.490s
user 0m0.467s
sys 0m0.000s
Even looking at just the user times, the gain is in the right direction
and is a fair percentage...
According to ZEND_BEGIN_SILENCE, just try to run simple script <?php $x =
@$y;?> with and without this check.
In case of missing check, real $y fetch is performed in ASSIGN operator
after ZEND_END_SILENCE, so we see error message.
Ah, of course, that makes perfect sense... And I've got to say, that's
a clever solution to that problem. It does unnecessarily rob DIM/OBJ
fetches in a localized silence ($foo = @$bar[$baz];) of being CV when
those technically could, but that's a fairly small price to pay for the
elegance of the solution.
So leaving the silence alone (since it's necessary), and considering the
appearant gain for a minor code change, what are your thoughts on
tossing this in as is and looking at extending it for $GLOBALS['foo'] ->
(global fetch CV)$foo later on?
-Sara
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