zend introduce const GNUC attribute. sub optimisation where there is no pointers, nor particular memory layout, thread local/volatile ... involved. usage concealed for now into little pack helpers.

Closes php#9326.

Author: devnexen

Zend/zend_portability.h

@@ -228,6 +228,12 @@ char *alloca();
 # define ZEND_ATTRIBUTE_ALLOC_SIZE2(X,Y)
 #endif
 
+#if ZEND_GCC_VERSION >= 3000
+# define ZEND_ATTRIBUTE_CONST __attribute__((const))
+#else
+# define ZEND_ATTRIBUTE_CONST
+#endif
+
 #if ZEND_GCC_VERSION >= 2007 || __has_attribute(format)
 # define ZEND_ATTRIBUTE_FORMAT(type, idx, first) __attribute__ ((format(type, idx, first)))
 #else

ext/standard/pack.c

@@ -102,13 +102,13 @@ static void php_pack(zval *val, size_t size, int *map, char *output)
 }
 /* }}} */
 
-static inline uint16_t php_pack_reverse_int16(uint16_t arg)
+ZEND_ATTRIBUTE_CONST static inline uint16_t php_pack_reverse_int16(uint16_t arg)
 {
 	return ((arg & 0xFF) << 8) | ((arg >> 8) & 0xFF);
 }
 
 /* {{{ php_pack_reverse_int32 */
-static inline uint32_t php_pack_reverse_int32(uint32_t arg)
+ZEND_ATTRIBUTE_CONST static inline uint32_t php_pack_reverse_int32(uint32_t arg)
 {
 	uint32_t result;
 	result = ((arg & 0xFF) << 24) | ((arg & 0xFF00) << 8) | ((arg >> 8) & 0xFF00) | ((arg >> 24) & 0xFF);