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Date: Mon, 14 Mar 2016 14:58:25 +0300
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Subject: Re: Remove useless opcode handlers
From: dmitry@zend.com (Dmitry Stogov)

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On 03/14/2016 02:29 PM, Nikita Popov wrote:
> On Mon, Mar 14, 2016 at 11:56 AM, Dmitry Stogov <dmitry@zend.com 
> <mailto:dmitry@zend.com>> wrote:
>
>     Please take a quick look and let me know if you see any problems.
>
>
>     https://gist.github.com/dstogov/23cc318dd3e411904e10
>
>
>     I'm going to commit this tomorrow.
>
>
>     Thanks. Dmitry.
>
> ZEND_ADD is not commutative for array operands.

Unfortunately, you are right :(
> ZEND_MUL may not be commutative if operator overloading is involved 
> (e.g. matrix multiplication is not abelian).

Right again.

> The NO_CONST_CONST cases are problematic: Opcache currently, in my 
> eyes incorrectly, evaluates constant expressions even if they throw 
> notices (currently I think mostly by suppressing them). If we do not 
> evaluate these, we may end up with CONST_CONST operations. (This is 
> not a huge problem just now because constant folding in opcache is 
> limited -- however with full constant propagation this leads to many 
> test failures.)

The patch adds NO_CONST_CONST handling to opcache. All tests are passed, 
I also didn't see any problems running ~10 real-life apps.

> The opcodes affected by the last point (limited to those included in 
> your patch) are SUB, MUL, POW, CONCAT (array operands) and BW_NOT 
> (various). However with Andrea's invalid numeric string RFC more will 
> fall in this category (evaluable but throwing).

I didn't get what is wrong with SUB, MUL, etc, because they are 
evaluated at compile-time
Anyway, I see - the patch can't be committed in current state.
Thanks for review.

Dmitry.

>
> Nikita


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