Description:
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There appears to be a performance regression in the CFG and DFA based optimization passes of OPcache in PHP 5.6+ when loading huge classes (such as those generated by Symfony's routing component) for the first time.

The issue does not occur on PHP 5.5. Tests below are with 5.6.30, 7.0.16 and 7.1.2 and default INI settings; I replicated the issue on both macOS and Linux.

Test file here (it's from an actual application, slightly anonymized, not a synthetic example): https://gist.github.com/dzuelke/fe867f55f09e0bf79ecefcc815b7fe92

Without OPcache, everything is fine in all versions:

$ time -p php -dopcache.enable_cli=0 hugeclass.php 
real 0.10
user 0.09
sys 0.00

With OPcache on, things are suddenly much, much slower:

5.6:

$ time -p php -dopcache.enable_cli=1 hugeclass.php
real 3.23
user 3.21
sys 0.02

7.0:

$ time -p php -dopcache.enable_cli=1 hugeclass.php
real 1.76
user 1.73
sys 0.02

7.1:

$ time -p php -dopcache.enable_cli=1 hugeclass.php
real 4.01
user 3.98
sys 0.02

For comparison, 5.5 is as speedy as you'd expect it to be:

$ time -p php -dopcache.enable_cli=1 hugeclass.php 
real 0.14
user 0.11
sys 0.02

If we switch off optimization passes 5 (CFG based) and 6 (DFA based, only in 7.1), everything is great again in all versions:

$ time -p php -dopcache.enable_cli=1 -dopcache.optimization_level=0x7FFFFFCF hugeclass.php
real 0.13
user 0.10
sys 0.02

For 5.6 and 7.0, pass 6 is not a thing, but in 7.1, we can inspect passes 5 and 6 separately.

Pass 5 (CFG based) already makes for a drastic performance hit in 7.1:

$ time -p php -dopcache.enable_cli=1 -dopcache.optimization_level=0x7FFFFFDF hugeclass.php
real 0.88
user 0.86
sys 0.01

But pass 6 (DFA based) is the one that causes the biggest slowdown in 7.1:

$ time -p php -dopcache.enable_cli=1 -dopcache.optimization_level=0x7FFFFFEF hugeclass.php
real 3.29
user 3.24
sys 0.04

In all versions, subsequent loads from the cache (such as when running FPM or the built-in web server) are fast.

Confirmed as bug in both CFG and DFA passes by Nikita: http://news.php.net/php.internals/98518

Test script:
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https://gist.github.com/dzuelke/fe867f55f09e0bf79ecefcc815b7fe92