Bug #80404 [Ver->Csd]: Incorrect range inference result when division results in float
Edit report at https://bugs.php.net/bug.php?id=80404&edit=1
ID: 80404
Updated by: nikic@php.net
Reported by: contact at shivammathur dot com
Summary: Incorrect range inference result when division
results in float
-Status: Verified
+Status: Closed
Type: Bug
Package: opcache
Operating System: Tested on Ubuntu 18.04
PHP Version: 8.0Git-2020-11-23 (Git)
Block user comment: N
Private report: N
New Comment:
Automatic comment on behalf of nikita.ppv@gmail.com
Revision: http://git.php.net/?p=php-src.git;a=commit;h=03f8bccaf545817237ee5b92a0cad6aefbe4e603
Log: Fixed bug #80404
Previous Comments:
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[2020-11-24 09:20:48] nikic@php.net
0000 ASSIGN #0.CV0($firstRowColumns) [undef, ref, any] -> #1.CV0($firstRowColumns) [ref, any]
RANGE[63..63] int(63)
0001 INIT_FCALL 1 96 string("var_dump")
0002 #2.T1 [false, long, double, object] RANGE[0..0] = DIV #1.CV0($firstRowColumns) [ref, any]
RANGE[63..63] int(120)
0003 #3.T2 [false, long, double, object] RANGE[0..0] = MUL #2.T1 [false, long, double, object]
RANGE[0..0] int(100)
0004 #4.T1 [long] RANGE[0..0] = CAST (long) #3.T2 [false, long, double, object] RANGE[0..0]
0005 SEND_VAL #4.T1 [long] RANGE[0..0] 1
0006 DO_ICALL
0007 RETURN int(1)
Interesting issue. We determine that ($firstRowColumns / 120) has value range 0..0 and thus that
($firstRowColumns / 120) * 100 stays zero.
We probably shouldn't be rounding down the division. While that's the behavior of integer
divisions, it does not accurately model PHP's fallback to float division.
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[2020-11-23 14:12:24] cmb@php.net
Ah, thanks!
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[2020-11-23 11:59:03] contact at shivammathur dot com
@cmb
Can be reproduced with opcache.jit=off, so I'm not sure if this is JIT related.
Jit Status - https://github.com/shivammathur/test-setup-php/runs/1441867898?check_suite_focus=true#step:5:67
Test - https://github.com/shivammathur/test-setup-php/runs/1441867898?check_suite_focus=true#step:6:33
------------------------------------------------------------------------
[2020-11-23 11:53:08] cmb@php.net
This looks like a JIT issue.
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[2020-11-23 10:06:00] contact at shivammathur dot com
Description:
------------
PHP 8.0.0-dev (cli) (built: Nov 23 2020 00:27:07) ( NTS )
Copyright (c) The PHP Group
Zend Engine v4.0.0-dev, Copyright (c) Zend Technologies
with Zend OPcache v8.0.0-dev, Copyright (c), by Zend Technologies
Build Configuration: https://github.com/shivammathur/php-builder/blob/master/.github/scripts/8.0
Script: https://3v4l.org/kkRIE
curl -o test.php -H Accept:text/plain -sL https://3v4l.org/kkRIE
for ((i=1;i<=5;i++));
do
echo $i
php test.php
sleep 1
done
Above snippet will run the script "https://3v4l.org/kkRIE" multiple times and when opcache
kicks in "(int) (63/ 120 * 100)" starts evaluating to 0.
This works fine with opcache disabled on PHP 8.0 and with or without opcache on PHP 7.4
Test workflow - https://github.com/shivammathur/test-setup-php/runs/1441325553?check_suite_focus=true#step:6:33
Test script:
---------------
<?php
$firstRowColumns = 63;
var_dump([
$firstRowColumns,
($firstRowColumns / 120),
($firstRowColumns / 120 * 100),
(int) ($firstRowColumns / 120 * 100),
]);
Expected result:
----------------
(int) (63/ 120 * 100) should evaluate to 52 with opcache enabled on PHP 8.0
Actual result:
--------------
(int) (63/ 120 * 100) evaluates to 0 with opcache enabled on PHP 8.0
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Edit this bug report at https://bugs.php.net/bug.php?id=80404&edit=1
Thread (6 messages)