[Bug 1458434] [NEW] Use __builtin_clzl on POWER

[Daniel Axtens]

Public bug reported:

Zend/zend_alloc.c uses __builtin_clzl in zend_mm_high_bit and
zend_mm_low_but, but only if (defined(__arm__) ||
defined(__aarch64__)). This is overly restrictive: it's also usable if
__defined__(__powerpc__).

This causes a bump to speed on POWER systems: previously
zend_mm_high_bit shows up on perf reports, with this patch the functions
drop out of the profile entirely.

This bug has also been reported upstream
(https://bugs.php.net/bug.php?id=69703), but I've sent you this report,
along with a `dpkg-source --commit` style patch, in the hopes that
you'll pick it up, so that Ubuntu users get the performance improvement
sooner.

This patch was built and tested on Vivid, but is applicable to a range
of PHP versions.

** Affects: php5 (Ubuntu)
     Importance: Undecided
         Status: New

** Attachment added: "__builtin_clzl.patch"
   https://bugs.launchpad.net/bugs/1458434/+attachment/4403858/+files/__builtin_clzl.patch

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https://bugs.launchpad.net/bugs/1458434

Title:
  Use __builtin_clzl on POWER

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