Performance degradation introduced in 2.1.41

[Zombaya]

Bug report

Summary

Upgrading PHPStan to the latest version caused a severe performance regression.

Before the upgrade, analysis of the affected code took about 10 minutes. After upgrading, the analysis did not complete even after 45 minutes, and subprocesses eventually timed out.

Regression range

I was able to narrow the issue down to version 2.1.41.

• 2.1.40: works normally
• 2.1.41: severe slowdown / extremely long analysis time

Reproduction

I created a minimal repository to reproduce the issue:

https://github.com/Zombaya/phpstan-2_1_41-performance-degradation

I tried to reduce the example as much as possible, but I could not simplify it further without knowing more about how PHPStan analyzes it internally. Removing some seemingly unrelated lines suddenly removed any slowdowns.

Observed behavior

There are two relevant files/classes in the reproduction:

• Slow.php
• NeverEnding.php

The files are effectively the same, except that Slow.php has one code block commented out.

That commented-out block still makes analysis on 2.1.41 much slower than on 2.1.40, but it does not cause the analysis to become endlessly slow.

When the code block is present, NeverEnding.php becomes even slower to analyze.

Timing results

File	Time on 2.1.40	Time on 2.1.41
Slow.php	0.3s	3.5s
NeverEnding.php	0.3s	14m 50s

Test command

I tested the timings using: vendor/bin/phpstan a --level=0 -vvv --debug src/Slow.php

Sample output of NeverEnding

$ vendor/bin/phpstan a --level=8 -vvv --debug src/NeverEnding.php 
Result cache not used because of debug mode.
/home/int8/phpstan-performance-degradation/src/NeverEnding.php
--- consumed 36.5 MB, total 84.5 MB, took 889.92 s, 0.093 LoC/s
Result cache was not saved because only files were passed as analysed paths.
 ------ ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ 
  Line   NeverEnding.php                                                                                                                                                                           
 ------ ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ 
  12     Method Zombaya\PhpstanPerformanceDegradation\NeverEnding::foo() has parameter $input with generic class Symfony\Component\HttpFoundation\InputBag but does not specify its types: TInput  
         🪪  missingType.generics                                                                                                                                                                  
  69     Parameter #1 $type of static method Zombaya\PhpstanPerformanceDegradation\Shared::calculateThings() expects int|null, bool|float|int|string|null given.                                   
         🪪  argument.type                                                                                                                                                                         
 ------ ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ 


                                                                                                                        
 [ERROR] Found 2 errors                                                                                                 
                                                                                                                        

PHP runtime version: 8.2.30
PHP version for analysis: 8.2.30 (from runtime)

PHPStan version: 2.1.41
PHPStan running from:
/home/int8/phpstan-performance-degradation/vendor/phpstan/phpstan

Extension installer: Not installed

Discovered Composer project root:
/home/int8/phpstan-performance-degradation

Parallel processing scheduler:
# of detected CPU cores:   8
# of analysed files:       1
# of jobs:                 1
# of spawned processes:    1

Elapsed time: 14 minutes 50 seconds
Used memory: 84.5 MB

Code snippet that reproduces the problem

No response

Expected output

I expect the repro-project to be able to be analyzed within 1 second.

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[mergeable]

This bug report is missing a link to reproduction at phpstan.org/try.

It will most likely be closed after manual review.

[staabm]

thanks for the reproducer.

I used the new phpstan-bisect feature currently available in 2.1.x-dev to narrow the root cause:

$ composer update --with phpstan/phpstan:2.1.x-dev
Loading composer repositories with package information
Updating dependencies
Lock file operations: 0 installs, 1 update, 0 removals
  - Upgrading phpstan/phpstan (2.1.46 => 2.1.x-dev b12745b)
Writing lock file
...
$ php vendor/bin/phpstan bisect --level=0 -vvv src/Slow.php

 Enter the good (working) PHPStan release version (e.g. 2.1.0):
 > 2.1.40

 Enter the bad (broken) PHPStan release version (e.g. 2.1.5):
 > 2.1.41

Fetching commits between 2.1.40 and 2.1.41...
---------------------------------------------

Found 115 commits between 2.1.40 and 2.1.41.
100 of them change phpstan.phar.

Testing commit da3e0e6 (Updated PHPStan to commit da3e0e6509224c4feec9f1ba648deaa1a8c288ff) [~7 steps left]
-----------------------------------------------------------------------------------------------------------

Downloading phpstan.phar...
 [============================] 100% 26.12 MB
Running analysis...

Result cache not used because only files were passed as analysed paths.
Result cache was not saved because only files were passed as analysed paths.

 [OK] No errors                                                                                                         

PHP runtime version: 8.3.30
PHP version for analysis: 8.3.30 (from runtime)

PHPStan version: 2.1.x-dev@da3e0e6
PHPStan running from:
/private/var/folders/yj/hdlshb_n3c7db27tndnsvxqw0000gn/T/phpstan-bisect

Extension installer: Not installed

Discovered Composer project root:
/Users/staabm/workspace/phpstan-src/tmp/phpstan-2_1_41-performance-degradation

Parallel processing scheduler:
# of detected CPU cores:   14
# of analysed files:       1
# of jobs:                 1
# of spawned processes:    1

Elapsed time: 3.34 seconds
Used memory: 94.92 MB

Analysis exited with code: 0

 Is this result good or bad?:
  [0] good
  [1] bad
 > bad

Testing commit a752f73 (Updated PHPStan to commit a752f73c9715c9bf39970112900310eee87d0125) [~6 steps left]
-----------------------------------------------------------------------------------------------------------

Downloading phpstan.phar...
 [============================] 100% 26.00 MB
Running analysis...

Result cache not used because only files were passed as analysed paths.
Result cache was not saved because only files were passed as analysed paths.

 [OK] No errors                                                                                                         

PHP runtime version: 8.3.30
PHP version for analysis: 8.3.30 (from runtime)

PHPStan version: 2.1.x-dev@a752f73
PHPStan running from:
/private/var/folders/yj/hdlshb_n3c7db27tndnsvxqw0000gn/T/phpstan-bisect

Extension installer: Not installed

Discovered Composer project root:
/Users/staabm/workspace/phpstan-src/tmp/phpstan-2_1_41-performance-degradation

Parallel processing scheduler:
# of detected CPU cores:   14
# of analysed files:       1
# of jobs:                 1
# of spawned processes:    1

Elapsed time: 0.52 seconds
Used memory: 96.8 MB

Analysis exited with code: 0

 Is this result good or bad?:
  [0] good
  [1] bad
 > good

Testing commit f08de42 (Updated PHPStan to commit f08de4291d5174440a2e35eb10f06e3570beaf89) [~5 steps left]
-----------------------------------------------------------------------------------------------------------

Downloading phpstan.phar...
 [============================] 100% 26.00 MB
Running analysis...

Result cache not used because only files were passed as analysed paths.
Result cache was not saved because only files were passed as analysed paths.

 [OK] No errors                                                                                                         

PHP runtime version: 8.3.30
PHP version for analysis: 8.3.30 (from runtime)

PHPStan version: 2.1.x-dev@f08de42
PHPStan running from:
/private/var/folders/yj/hdlshb_n3c7db27tndnsvxqw0000gn/T/phpstan-bisect

Extension installer: Not installed

Discovered Composer project root:
/Users/staabm/workspace/phpstan-src/tmp/phpstan-2_1_41-performance-degradation

Parallel processing scheduler:
# of detected CPU cores:   14
# of analysed files:       1
# of jobs:                 1
# of spawned processes:    1

Elapsed time: 0.52 seconds
Used memory: 94.81 MB

Analysis exited with code: 0

 Is this result good or bad?:
  [0] good
  [1] bad
 > good

Testing commit afd310d (Updated PHPStan to commit afd310d3026c8611f34b402bc039be9e3f31a97a) [~4 steps left]
-----------------------------------------------------------------------------------------------------------

Downloading phpstan.phar...
 [============================] 100% 26.03 MB
Running analysis...

Result cache not used because only files were passed as analysed paths.
Result cache was not saved because only files were passed as analysed paths.

 [OK] No errors                                                                                                         

PHP runtime version: 8.3.30
PHP version for analysis: 8.3.30 (from runtime)

PHPStan version: 2.1.x-dev@afd310d
PHPStan running from:
/private/var/folders/yj/hdlshb_n3c7db27tndnsvxqw0000gn/T/phpstan-bisect

Extension installer: Not installed

Discovered Composer project root:
/Users/staabm/workspace/phpstan-src/tmp/phpstan-2_1_41-performance-degradation

Parallel processing scheduler:
# of detected CPU cores:   14
# of analysed files:       1
# of jobs:                 1
# of spawned processes:    1

Elapsed time: 3.34 seconds
Used memory: 94.83 MB

Analysis exited with code: 0

 Is this result good or bad?:
  [0] good
  [1] bad
 > bad

Testing commit cf070ae (Updated PHPStan to commit cf070aedfc960690dd37fa43f5d24c758d33a1ec) [~3 steps left]
-----------------------------------------------------------------------------------------------------------

Downloading phpstan.phar...
 [============================] 100% 26.03 MB
Running analysis...

Result cache not used because only files were passed as analysed paths.
Result cache was not saved because only files were passed as analysed paths.

 [OK] No errors                                                                                                         

PHP runtime version: 8.3.30
PHP version for analysis: 8.3.30 (from runtime)

PHPStan version: 2.1.x-dev@cf070ae
PHPStan running from:
/private/var/folders/yj/hdlshb_n3c7db27tndnsvxqw0000gn/T/phpstan-bisect

Extension installer: Not installed

Discovered Composer project root:
/Users/staabm/workspace/phpstan-src/tmp/phpstan-2_1_41-performance-degradation

Parallel processing scheduler:
# of detected CPU cores:   14
# of analysed files:       1
# of jobs:                 1
# of spawned processes:    1

Elapsed time: 3.34 seconds
Used memory: 94.83 MB

Analysis exited with code: 0

 Is this result good or bad?:
  [0] good
  [1] bad
 > bad

Testing commit 0c740e3 (Updated PHPStan to commit 0c740e396cb0ce11d344594e4118b6fb9f3d5197) [~2 steps left]
-----------------------------------------------------------------------------------------------------------

Downloading phpstan.phar...
 [============================] 100% 26.00 MB
Running analysis...

Result cache not used because only files were passed as analysed paths.
Result cache was not saved because only files were passed as analysed paths.

 [OK] No errors                                                                                                         

PHP runtime version: 8.3.30
PHP version for analysis: 8.3.30 (from runtime)

PHPStan version: 2.1.x-dev@0c740e3
PHPStan running from:
/private/var/folders/yj/hdlshb_n3c7db27tndnsvxqw0000gn/T/phpstan-bisect

Extension installer: Not installed

Discovered Composer project root:
/Users/staabm/workspace/phpstan-src/tmp/phpstan-2_1_41-performance-degradation

Parallel processing scheduler:
# of detected CPU cores:   14
# of analysed files:       1
# of jobs:                 1
# of spawned processes:    1

Elapsed time: 0.52 seconds
Used memory: 94.81 MB

Analysis exited with code: 0

 Is this result good or bad?:
  [0] good
  [1] bad
 > good

                                                                                                                        
 [OK] Found the first bad commit!                                                                                       
                                                                                                                        

Commit: cf070ae8756a1514e8e90b8d3721937c6159b4e1
URL:    https://github.com/phpstan/phpstan/commit/cf070ae8756a1514e8e90b8d3721937c6159b4e1

Commit message:
Updated PHPStan to commit cf070aedfc960690dd37fa43f5d24c758d33a1ec

https://github.com/phpstan/phpstan-src/commit/cf070aedfc960690dd37fa43f5d24c758d33a1ec Tip about adding `@phpstan-impure` where applicable

Related phpstan-src commits:
  https://github.com/phpstan/phpstan-src/commit/cf070aedfc960690dd37fa43f5d24c758d33a1ec Tip about adding `@phpstan-impure` where applicable

this tells us root cause is in phpstan/phpstan-src@cf070ae

---

I was also running blackfire run php vendor/bin/phpstan analyze --level=0 -vvv --debug src/Slow.php on the slow repro

https://blackfire.io/profiles/69afe091-6fbc-4a8c-90f6-b46f9f218254/graph

it seems there is some big intersection/union type involved

[staabm]

disabling rememberPossiblyImpureFunctionValues: false in the phpstan.neon config makes the reproducer fast again
(even the "never ending" one finishes in 0.3 seconds, with rememberPossiblyImpureFunctionValues: false)

[phpstan-bot]

Closed via merging phpstan/phpstan-src#5441