Adjust default value of opcache.jit_hot_loop to a prime number

Loops whose number of iterations + 1 is a factor of opcache.jit_hot_loop
will always be traced at the exact moment the loop condition evaluates
to false. As a result, these loops can never be JIT'ed successfully.

Here I adjust the default value of opcache.jit_hot_loop to a prime number,
so this can not happen (unless number of iterations+1 is opcache.jit_hot_loop).

Closes GH-18573

Author: arnaud-lb

NEWS

@@ -111,9 +111,10 @@ PHP                                                                        NEWS
   . Added mysqlnd.collect_memory_statistics to ini quick reference.
     (hauk92)
 
-- OPcache:
+- Opcache:
   . Fixed ZTS OPcache build on Cygwin. (cmb)
   . Added opcache.file_cache_read_only. (Samuel Melrose)
+  . Updated default value of opcache.jit_hot_loop. (Arnaud)
 
 - Output:
   . Fixed calculation of aligned buffer size. (cmb)

UPGRADING

@@ -460,6 +460,9 @@ PHP 8.5 UPGRADE NOTES
     Note: A cache generated with a different build of PHP, a different file
     path, or different settings (including which extensions are loaded), may be
     ignored.
+  . The default value of opcache.jit_hot_loop is now 61 (a prime) to prevent it
+    from being a multiple of loop iteration counts.
+    It is recommended that this parameter is set to a prime number.
 
 ========================================
 12. Windows Support

ext/opcache/zend_accelerator_module.c

@@ -323,7 +323,8 @@ ZEND_INI_BEGIN()
 	STD_PHP_INI_ENTRY("opcache.jit_max_root_traces"           , "1024",                       PHP_INI_SYSTEM, OnUpdateLong,     max_root_traces,       zend_jit_globals, jit_globals)
 	STD_PHP_INI_ENTRY("opcache.jit_max_side_traces"           , "128",                        PHP_INI_SYSTEM, OnUpdateLong,     max_side_traces,       zend_jit_globals, jit_globals)
 	STD_PHP_INI_ENTRY("opcache.jit_max_exit_counters"         , "8192",                       PHP_INI_SYSTEM, OnUpdateLong,     max_exit_counters,     zend_jit_globals, jit_globals)
-	STD_PHP_INI_ENTRY("opcache.jit_hot_loop"                  , "64",                         PHP_INI_SYSTEM, OnUpdateCounter,  hot_loop,              zend_jit_globals, jit_globals)
+	/* Defautl value should be a prime number, to reduce the chances of loop iterations being a factor of opcache.jit_hot_loop */
+	STD_PHP_INI_ENTRY("opcache.jit_hot_loop"                  , "61",                         PHP_INI_SYSTEM, OnUpdateCounter,  hot_loop,              zend_jit_globals, jit_globals)
 	STD_PHP_INI_ENTRY("opcache.jit_hot_func"                  , "127",                        PHP_INI_SYSTEM, OnUpdateCounter,  hot_func,              zend_jit_globals, jit_globals)
 	STD_PHP_INI_ENTRY("opcache.jit_hot_return"                , "8",                          PHP_INI_SYSTEM, OnUpdateCounter,  hot_return,            zend_jit_globals, jit_globals)
 	STD_PHP_INI_ENTRY("opcache.jit_hot_side_exit"             , "8",                          PHP_INI_ALL,    OnUpdateCounter,  hot_side_exit,         zend_jit_globals, jit_globals)