Bug #72335 [NEW]: Misoptimize due to type narrowing

From: nikic Operating system: PHP version: master-Git-2016-06-04 (Git) Package: opcache Bug Type: Bug Bug description:Misoptimize due to type narrowing Description: ------------ We perform (long|double)->double narrowing even if chains of operations that only eventually result in a double are involved. This can lead to wrong results because parts of the calculation that would have been performed on integers are performed on doubles instead, with the corresponding loss in precision. We need to either not narrow for such chains or ensure that the transformation is safe. Test script: --------------- <?php function test() { $b = false; $x = (1<<53)+1; do { $x = 1.0 * ($x - (1<<53)); } while ($b); return $x; } var_dump(test()); Expected result: ---------------- float(1) Actual result: -------------- float(0) -- Edit bug report at https://bugs.php.net/bug.php?id=72335&edit=1 -- Try a snapshot (PHP 5.4): https://bugs.php.net/fix.php?id=72335&r=trysnapshot54 Try a snapshot (PHP 5.5): https://bugs.php.net/fix.php?id=72335&r=trysnapshot55 Try a snapshot (trunk): https://bugs.php.net/fix.php?id=72335&r=trysnapshottrunk Fixed in SVN: https://bugs.php.net/fix.php?id=72335&r=fixed Fixed in release: https://bugs.php.net/fix.php?id=72335&r=alreadyfixed Need backtrace: https://bugs.php.net/fix.php?id=72335&r=needtrace Need Reproduce Script: https://bugs.php.net/fix.php?id=72335&r=needscript Try newer version: https://bugs.php.net/fix.php?id=72335&r=oldversion Not developer issue: https://bugs.php.net/fix.php?id=72335&r=support Expected behavior: https://bugs.php.net/fix.php?id=72335&r=notwrong Not enough info: https://bugs.php.net/fix.php?id=72335&r=notenoughinfo Submitted twice: https://bugs.php.net/fix.php?id=72335&r=submittedtwice register_globals: https://bugs.php.net/fix.php?id=72335&r=globals PHP 4 support discontinued: https://bugs.php.net/fix.php?id=72335&r=php4 Daylight Savings: https://bugs.php.net/fix.php?id=72335&r=dst IIS Stability: https://bugs.php.net/fix.php?id=72335&r=isapi Install GNU Sed: https://bugs.php.net/fix.php?id=72335&r=gnused Floating point limitations: https://bugs.php.net/fix.php?id=72335&r=float No Zend Extensions: https://bugs.php.net/fix.php?id=72335&r=nozend MySQL Configuration Error: https://bugs.php.net/fix.php?id=72335&r=mysqlcfg