Object getter method optimization

Hi Xinchen Hui,

The magic get method is not being optimized. This optimization only
focuses on simple getter, which is used in a lot of OO-based appoications
like Symfony or Drupal.

Hi Dimitry,

Thanks for reviewing the code, comments are helpful. :) could you explain a
little bit of how runtime_cache_slot works?

I think adding the property_offset in op_array is kinda like a workaround
for POC, and I want to remove it from op_array.

Cheers, Yo-An

Xinchen Hui laruence@php.net 於 2016年4月1日 星期五寫道：

Hey:

On Fri, Apr 1, 2016 at 4:35 PM, Lin Yo-An <cornelius.howl@gmail.com
javascript:_e(%7B%7D,'cvml','cornelius.howl@gmail.com');> wrote:

Hi Dmitry, Nikita, Andrea

My implementation now is able to get the property offset and fetch object
property directly without invoking zend_std_read_property and pushing new
call frame onto the stack.

The current behavior:

1. In compile-time, the pass_two() function now marks the getter
   functions in op_array.accessor.type

2. When Zend Engine first time attempt to read the property, it saves the
   property offset in the accessor field and mark the method as a "getter".

I am not sure if I understand you correctly, but.. have you consider this
case?

<?php
class A {
private $a = 1;
private $b = 2;
public function __get($name) {
static $is_first = 1;
if ($is_first) {
$is_first = 0;
return $this->a;
} else {
return $this->b;
}
}
}

$a = new A();
echo $a->nomeaning;
echo $a->nomeaning;
?>

thanks

3. When Zend Engine second time invoke the getter method, it checks the
   accessor field and try to read the property value directly instead a
   "method call"

The implementation did some change:

1. Added accessor struct to op_array to save "accessor" related
   information (getter or setter, property offset)

2. Added two statement in zend_std_read_property to save property offset.

3. Added op code check in zend_compile (The pass_two() function) to mark
   a function is a getter)

But now I encountered a problem, I can't store the result value in
INIT_METHOD_CALL op, the result var is only available in DO_FCALL_*

I have an idea for solving this, but I'm not sure if it's good or not:

If DO_FCALL_* will always follow a INIT_METHOD_CALL, then I think we can
store result var from the next op (DO_FCALL) and skip DO_FCALL directly.

Would be great if I can have your advices and suggestion. :-)

Thanks, Yo-An Lin

On Tue, Mar 22, 2016 at 4:45 PM, Dmitry Stogov <dmitry@zend.com
javascript:_e(%7B%7D,'cvml','dmitry@zend.com');> wrote:

Hi Yo-An Lin,

This "run-time inlining" approach may work.

PHP compiler (or optimizer) may mark functions and methods suitable for
"run-time" inlining (e.g. methods without arguments and FETCH_OBJ_R UNUSED,
CONST -> TMP; RETURN TMP).

Then INIT_METHOD_CALL may check this flag and execute "optimized code
sequence" instead of pushing stack frame and real call.

However, I'm not sure what kind of performance impact this may make,
because we will have to make additional check on each INIT_METHOD_CALL
execution.

Thanks. Dmitry.

---

From: Lin Yo-An <cornelius.howl@gmail.com
javascript:_e(%7B%7D,'cvml','cornelius.howl@gmail.com');>
Sent: Saturday, March 19, 2016 10:08
To: Dmitry Stogov
Cc: internals; Xinchen Hui
Subject: Re: [PHP-DEV] Object getter method optimization

Hi Dmitry,

Thanks for your reply! You're correct. let me try to explain your points:

If I have a main.php and worker.php

And I defined work($worker) { $status = $worker->getStatus(); } inside
main.php

when main.php is compiled, we don't know what the class entry of $worker
is. What we only know is invoking a method "getStatus" on $worker CV unless
we know we have to compile worker.php before main.php and add a type hint
on $worker.

Is it correct?

Since the original approach doesn't work, here comes another new idea:

When executing method call on an object, if we found the method body are
just 2 op codes (FETCH_OBJ_R and RETURN), we then denote the method is a
"getter method"

And the next time, when we execute the same method, we found the "getter
method" flag, we simply execute FETCH_OBJ_R on that object and return the
value to avoid extra op code execution time.

Do you think if this could work?

Best Regards and Thanks for your work on PHP VM
Yo-An Lin

On Fri, Mar 18, 2016 at 3:36 PM, Dmitry Stogov <dmitry@zend.com
javascript:_e(%7B%7D,'cvml','dmitry@zend.com');> wrote:

Hi Yo-An Lin,

Unfortunately, this approach won't work.
At first, at compile time we don't know the body of called getter.
At second, the called method might be changed even at run-time, because
of polymorphism.

Tricks like this might be implemented using JIT and polymorphic inline
caches.

Thanks. Dmitry.

---

From: Lin Yo-An <cornelius.howl@gmail.com
javascript:_e(%7B%7D,'cvml','cornelius.howl@gmail.com');>
Sent: Friday, March 18, 2016 05:23
To: internals
Subject: [PHP-DEV] Object getter method optimization

Hello Everyone,

I am recently trying to write an optimizer that could optimize the
getter
method call into just one object fetch opcode.

I'd like to know thoughts from you guys, here is the note:
https://c9s.hackpad.com/INLINE-OP-TVGo9WcshbZ

--
Best Regards,

Yo-An Lin
https://github.com/c9s

--
Best Regards,

Yo-An Lin

--
Best Regards,

Yo-An Lin

--
Xinchen Hui
@Laruence
http://www.laruence.com/

--
Sent from Gmail Mobile

I submitted my PR here https://github.com/php/php-src/pull/1847

Hi internals,

Here comes the result:

Without getter optimization (3 runs):

250.76603889465ms

With getter optimization (3 runs)

110.88299751282ms

Microbench result:
https://gist.github.com/c9s/0273ac21631562724cabf86c42e86e32

On Fri, Apr 1, 2016 at 4:35 PM, Lin Yo-An cornelius.howl@gmail.com
wrote:

Hi Dmitry, Nikita, Andrea

My implementation now is able to get the property offset and fetch object
property directly without invoking zend_std_read_property and pushing new
call frame onto the stack.

The current behavior:

1. In compile-time, the pass_two() function now marks the getter
   functions in op_array.accessor.type

2. When Zend Engine first time attempt to read the property, it saves the
   property offset in the accessor field and mark the method as a "getter".

3. When Zend Engine second time invoke the getter method, it checks the
   accessor field and try to read the property value directly instead a
   "method call"

The implementation did some change:

1. Added accessor struct to op_array to save "accessor" related
   information (getter or setter, property offset)

2. Added two statement in zend_std_read_property to save property offset.

3. Added op code check in zend_compile (The pass_two() function) to mark
   a function is a getter)

But now I encountered a problem, I can't store the result value in
INIT_METHOD_CALL op, the result var is only available in DO_FCALL_*

I have an idea for solving this, but I'm not sure if it's good or not:

If DO_FCALL_* will always follow a INIT_METHOD_CALL, then I think we can
store result var from the next op (DO_FCALL) and skip DO_FCALL directly.

Would be great if I can have your advices and suggestion. :-)

Thanks, Yo-An Lin

Hi Yo-An Lin,

This "run-time inlining" approach may work.

PHP compiler (or optimizer) may mark functions and methods suitable for
"run-time" inlining (e.g. methods without arguments and FETCH_OBJ_R UNUSED,
CONST -> TMP; RETURN TMP).

Then INIT_METHOD_CALL may check this flag and execute "optimized code
sequence" instead of pushing stack frame and real call.

However, I'm not sure what kind of performance impact this may make,
because we will have to make additional check on each INIT_METHOD_CALL
execution.

Thanks. Dmitry.

---

From: Lin Yo-An cornelius.howl@gmail.com
Sent: Saturday, March 19, 2016 10:08
To: Dmitry Stogov
Cc: internals; Xinchen Hui
Subject: Re: [PHP-DEV] Object getter method optimization

Hi Dmitry,

Thanks for your reply! You're correct. let me try to explain your points:

If I have a main.php and worker.php

And I defined work($worker) { $status = $worker->getStatus(); } inside
main.php

when main.php is compiled, we don't know what the class entry of $worker
is. What we only know is invoking a method "getStatus" on $worker CV unless
we know we have to compile worker.php before main.php and add a type hint
on $worker.

Is it correct?

Since the original approach doesn't work, here comes another new idea:

When executing method call on an object, if we found the method body are
just 2 op codes (FETCH_OBJ_R and RETURN), we then denote the method is a
"getter method"

And the next time, when we execute the same method, we found the "getter
method" flag, we simply execute FETCH_OBJ_R on that object and return the
value to avoid extra op code execution time.

Do you think if this could work?

Best Regards and Thanks for your work on PHP VM
Yo-An Lin

Hi Yo-An Lin,

Unfortunately, this approach won't work.
At first, at compile time we don't know the body of called getter.
At second, the called method might be changed even at run-time, because
of polymorphism.

Tricks like this might be implemented using JIT and polymorphic inline
caches.

Thanks. Dmitry.

---

From: Lin Yo-An cornelius.howl@gmail.com
Sent: Friday, March 18, 2016 05:23
To: internals
Subject: [PHP-DEV] Object getter method optimization

Hello Everyone,

I am recently trying to write an optimizer that could optimize the
getter
method call into just one object fetch opcode.

I'd like to know thoughts from you guys, here is the note:
https://c9s.hackpad.com/INLINE-OP-TVGo9WcshbZ

--
Best Regards,

Yo-An Lin
https://github.com/c9s

--
Best Regards,

Yo-An Lin

--
Best Regards,

Yo-An Lin

--
Best Regards,

Yo-An Lin

--
Best Regards,

Yo-An Lin