Hello,
Yesterday I was playing with branch prediction in the Zend VM executor.
Although I didn't have any noticeable performance improvement within the
bench.php script, I've put the patch on-line, because someone else might
want to mess with it too :) (but with care..)
patch: http://mega.ist.utl.pt/~ncpl/zend_branch_prediction.txt
gcc docs:
http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#index-g_t_005f_005fbuiltin_005fexpect-2440
the zend.h part of the patch is based on the similar macros (with the same
name, too) found in the Linux kernel.
I made & tested the patch in a Centrino laptop with gcc 3.4, so it might be
the cause of getting no relevant performance increase. On CPUs with longer
pipelines (like Pentium 4/NetBurst architecture), the performance increase
might be noticeable.
Happy hacking :)
Nuno
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