Eliminated run-time constant fetching for TRUE, FALSE and NULL

Author: dstogov

NEWS

@@ -1,6 +1,7 @@
 PHP                                                                        NEWS
 |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
 ?? Mar 2006, PHP 5.1.3RC2
+- Eliminated run-time constant fetching for TRUE, FALSE and NULL. (Dmitry)
 - Fixed offset/length parameter validation in substr_compare() function. (Ilia)
 - Added overflow checks to wordwrap() function. (Ilia)
 - Removed the E_STRICT deprecation notice from "var". (Ilia)

Zend/zend_compile.c

@@ -3095,20 +3095,49 @@ void zend_do_end_new_object(znode *result, znode *new_token, znode *argument_lis
 	*result = CG(active_op_array)->opcodes[new_token->u.opline_num].result;
 }
 
+static int zend_constant_ct_subst(znode *result, zval *const_name TSRMLS_DC)
+{
+	zend_constant *c = NULL;
+
+	if (zend_hash_find(EG(zend_constants), Z_STRVAL_P(const_name), Z_STRLEN_P(const_name)+1, (void **) &c) == FAILURE) {
+		char *lookup_name = zend_str_tolower_dup(Z_STRVAL_P(const_name), Z_STRLEN_P(const_name));
+		 
+		if (zend_hash_find(EG(zend_constants), lookup_name, Z_STRLEN_P(const_name)+1, (void **) &c)==SUCCESS) {
+			if ((c->flags & CONST_CS) && memcmp(c->name, Z_STRVAL_P(const_name), Z_STRLEN_P(const_name))!=0) {
+				c = NULL;
+			}
+		} else {
+			c = NULL;
+		}
+		efree(lookup_name);
+	}
+	if (c && (c->flags & CONST_CT_SUBST)) {
+		zval_dtor(const_name);
+		result->op_type = IS_CONST;
+		result->u.constant = c->value;
+		zval_copy_ctor(&result->u.constant);
+		INIT_PZVAL(&result->u.constant);
+		return 1;
+	}
+	return 0;
+}
+
 void zend_do_fetch_constant(znode *result, znode *constant_container, znode *constant_name, int mode TSRMLS_DC)
 {
 	switch (mode) {
 		case ZEND_CT:
 			if (constant_container) {
 				zend_do_fetch_class_name(NULL, constant_container, constant_name TSRMLS_CC);
 				*result = *constant_container;
-			} else {
+				result->u.constant.type = IS_CONSTANT;
+			} else if (!zend_constant_ct_subst(result, &constant_name->u.constant TSRMLS_CC)) {
 				*result = *constant_name;
+				result->u.constant.type = IS_CONSTANT;
 			}
-			result->u.constant.type = IS_CONSTANT;
 			break;
 		case ZEND_RT:
-			{
+			if (constant_container ||
+			    !zend_constant_ct_subst(result, &constant_name->u.constant TSRMLS_CC)) {
 				zend_op *opline = get_next_op(CG(active_op_array) TSRMLS_CC);
 
 				opline->opcode = ZEND_FETCH_CONSTANT;

Zend/zend_constants.c

@@ -114,8 +114,7 @@ void zend_register_standard_constants(TSRMLS_D)
 	{
 		zend_constant c;
 
-		c.value.type = IS_BOOL;
-		c.flags = CONST_PERSISTENT;
+		c.flags = CONST_PERSISTENT | CONST_CT_SUBST;
 		c.module_number = 0;
 
 		c.name = zend_strndup(ZEND_STRL("TRUE"));
@@ -130,16 +129,18 @@ void zend_register_standard_constants(TSRMLS_D)
 		c.value.type = IS_BOOL;
 		zend_register_constant(&c TSRMLS_CC);
 
+		c.name = zend_strndup(ZEND_STRL("NULL"));
+		c.name_len = sizeof("NULL");
+		c.value.type = IS_NULL;
+		zend_register_constant(&c TSRMLS_CC);
+
+		c.flags = CONST_PERSISTENT;
+
 		c.name = zend_strndup(ZEND_STRL("ZEND_THREAD_SAFE"));
 		c.name_len = sizeof("ZEND_THREAD_SAFE");
 		c.value.value.lval = ZTS_V;
 		c.value.type = IS_BOOL;
 		zend_register_constant(&c TSRMLS_CC);
-
-		c.name = zend_strndup(ZEND_STRL("NULL"));
-		c.name_len = sizeof("NULL");
-		c.value.type = IS_NULL;
-		zend_register_constant(&c TSRMLS_CC);
 	}
 }
 

Zend/zend_constants.h

@@ -26,6 +26,7 @@
 
 #define CONST_CS				(1<<0)				/* Case Sensitive */
 #define CONST_PERSISTENT		(1<<1)				/* Persistent */
+#define CONST_CT_SUBST			(2<<1)				/* Allow compile-time substitution */
 
 #define	PHP_USER_CONSTANT INT_MAX	/* a constant defined in user space */