Change default method of disabling JIT

Author: danog

UPGRADING

@@ -83,6 +83,12 @@ PHP 8.4 UPGRADE NOTES
     contain null bytes. This never actually worked correctly in the first place,
     which is why it throws an exception nowadays.
 
+- Opcache:
+  . JIT config defaults changed from `opcache.jit=tracing`, `opcache.jit_buffer_size=0` to `opcache.jit=disable`, `opcache.jit_buffer_size=64M`: this does not change the default behavior, JIT was and still is disabled by default, however now it is now disabled by default using the `opcache.jit` setting, not the `opcache.jit_buffer_size` setting.  
+  This may affect users who enabled JIT by only setting a different `opcache.jit_buffer_size`, without specifying a JIT mode with `opcache.jit`.  
+  To enable JIT, it is now required to populate the `opcache.jit` config value.
+  Also, `opcache.jit_buffer_size` now cannot be set to `0` if `opcache.jit` is set to a non-zero/disable/off value.  
+
 ========================================
 2. New Features
 ========================================

benchmark/benchmark.php

@@ -118,7 +118,8 @@ function runValgrindPhpCgiCommand(
         '-T' . ($warmup ? $warmup . ',' : '') . $repeat,
         '-d max_execution_time=0',
         '-d opcache.enable=1',
-        '-d opcache.jit_buffer_size=' . ($jit ? '128M' : '0'),
+        '-d opcache.jit=' . ($jit ? 'tracing' : 'disable'),
+        '-d opcache.jit_buffer_size=128M',
         '-d opcache.validate_timestamps=0',
         ...$args,
     ]);

ext/opcache/ZendAccelerator.c

@@ -3251,9 +3251,10 @@ static zend_result accel_post_startup(void)
 			if (JIT_G(buffer_size) == 0) {
 				JIT_G(enabled) = false;
 				JIT_G(on) = false;
-			} else if (!ZSMMG(reserved)) {
-				zend_accel_error_noreturn(ACCEL_LOG_FATAL, "Could not enable JIT: could not use reserved buffer!");
 			} else {
+				if (!ZSMMG(reserved)) {
+					zend_accel_error_noreturn(ACCEL_LOG_FATAL, "Could not enable JIT: could not use reserved buffer!");
+				}
 				zend_jit_startup(ZSMMG(reserved), jit_size, reattached);
 			}
 		}

ext/opcache/jit/zend_jit.h

@@ -47,7 +47,7 @@
 #define ZEND_JIT_REG_ALLOC_GLOBAL (1<<1) /* global linear scan register allocation */
 #define ZEND_JIT_CPU_AVX          (1<<2) /* use AVX instructions, if available */
 
-#define ZEND_JIT_DEFAULT_BUFFER_SIZE  "0"
+#define ZEND_JIT_DEFAULT_BUFFER_SIZE  "64m"
 
 #define ZEND_JIT_COUNTER_INIT         32531
 

ext/opcache/zend_accelerator_module.c

@@ -317,7 +317,7 @@ ZEND_INI_BEGIN()
 	STD_PHP_INI_ENTRY("opcache.cache_id"                      , ""    , PHP_INI_SYSTEM, OnUpdateString,           accel_directives.cache_id,               zend_accel_globals, accel_globals)
 #endif
 #ifdef HAVE_JIT
-	STD_PHP_INI_ENTRY("opcache.jit"                           , "tracing",                    PHP_INI_ALL,    OnUpdateJit,      options,               zend_jit_globals, jit_globals)
+	STD_PHP_INI_ENTRY("opcache.jit"                           , "disable",                    PHP_INI_ALL,    OnUpdateJit,      options,               zend_jit_globals, jit_globals)
 	STD_PHP_INI_ENTRY("opcache.jit_buffer_size"               , ZEND_JIT_DEFAULT_BUFFER_SIZE, PHP_INI_SYSTEM, OnUpdateLong,     buffer_size,           zend_jit_globals, jit_globals)
 	STD_PHP_INI_ENTRY("opcache.jit_debug"                     , "0",                          PHP_INI_ALL,    OnUpdateJitDebug, debug,                 zend_jit_globals, jit_globals)
 	STD_PHP_INI_ENTRY("opcache.jit_bisect_limit"              , "0",                          PHP_INI_ALL,    OnUpdateLong,     bisect_limit,          zend_jit_globals, jit_globals)

ext/phar/tests/024-opcache-win32.phpt

@@ -17,6 +17,7 @@ opcache.file_cache={PWD}/024-file_cache
 opcache.memory_consumption=64
 opcache.interned_strings_buffer=8
 opcache.max_accelerated_files=4000
+opcache.jit=tracing
 opcache.jit_buffer_size=64M
 opcache.revalidate_freq=60
 opcache.fast_shutdown=1