Pre operation lacking recording the variable use

[pbiggar]

Hello everyone,

  I've encountered a bug in phc on the pre operation handler. It's failing to record
a use that's making its definition getting killed on the DCE pass.

  More details as follow. Consider the program below:

<?php
  $i = $_ENV['x'];
  $i++;
  echo $i;
?>

After the first whole program iteration, the "$i = $_ENV['x']" gets kill on DCE, because
the instruction "$i++" is not recording the use for variable $i. This resulted in the
following program:

<?php
  $i++;
  echo $i;
?>

On the next iteration, the "$i" variable is not defined, hence its constant value can
be propagated as 0. So, 0++ equals to 1. The resultant (erroneous) optimized code is:

<?php
  echo 1;
?>

Original issue reported on code.google.com by logytech on 2010-09-21 02:00:06

[pbiggar]

Fixed on revision 3352.

Original issue reported on code.google.com by logytech on 2010-09-21 02:05:01

• Labels added: Priority-Low
• Labels removed: Priority-Medium