From: Dmitry Stogov <dmitry@zend.com>
Date: Wed, 1 Jul 2015 13:31:20 +0000 (+0300)
Subject: Cleanup (updated comments about optimization of comparison with IS_NULL)
X-Git-Tag: php-7.1.0alpha3~25^2~83
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=a0b55e6a3703268871dd53bd295d6bbc1fd890b0;p=php

Cleanup (updated comments about optimization of comparison with IS_NULL)
---

diff --git a/ext/opcache/Optimizer/block_pass.c b/ext/opcache/Optimizer/block_pass.c
index f4753ed080..a810829628 100644
--- a/ext/opcache/Optimizer/block_pass.c
+++ b/ext/opcache/Optimizer/block_pass.c
@@ -764,26 +764,30 @@ static void zend_optimize_block(zend_code_block *block, zend_op_array *op_array,
 			opline->opcode == ZEND_IS_NOT_EQUAL ||
 			opline->opcode == ZEND_CASE) {
 			if (ZEND_OP1_TYPE(opline) == IS_CONST &&
-// TODO: Optimization of comparison with null may be not safe ???
-#if 1
 				(Z_TYPE(ZEND_OP1_LITERAL(opline)) == IS_FALSE ||
 				 Z_TYPE(ZEND_OP1_LITERAL(opline)) == IS_TRUE)) {
-#else
-				 Z_TYPE(ZEND_OP1_LITERAL(opline)) <= IS_TRUE) {
-#endif
+				/* T = IS_EQUAL(TRUE,  X)     => T = BOOL(X) */
+				/* T = IS_EQUAL(FALSE, X)     => T = BOOL_NOT(X) */
+				/* T = IS_NOT_EQUAL(TRUE,  X) => T = BOOL_NOT(X) */
+				/* T = IS_NOT_EQUAL(FALSE, X) => T = BOOL(X) */
+				/* Optimization of comparison with "null" is not safe,
+				 * because ("0" == null) is not equal to !("0")
+				 */
 				opline->opcode =
 					((opline->opcode != ZEND_IS_NOT_EQUAL) == ((Z_TYPE(ZEND_OP1_LITERAL(opline))) == IS_TRUE)) ?
 					ZEND_BOOL : ZEND_BOOL_NOT;
 				COPY_NODE(opline->op1, opline->op2);
 				SET_UNUSED(opline->op2);
 			} else if (ZEND_OP2_TYPE(opline) == IS_CONST &&
-// TODO: Optimization of comparison with null may be not safe ???
-#if 1
 					   (Z_TYPE(ZEND_OP2_LITERAL(opline)) == IS_FALSE ||
 					    Z_TYPE(ZEND_OP2_LITERAL(opline)) == IS_TRUE)) {
-#else
-					    Z_TYPE(ZEND_OP2_LITERAL(opline)) <= IS_TRUE) {
-#endif
+				/* T = IS_EQUAL(X, TRUE)      => T = BOOL(X) */
+				/* T = IS_EQUAL(X, FALSE)     => T = BOOL_NOT(X) */
+				/* T = IS_NOT_EQUAL(X, TRUE)  => T = BOOL_NOT(X) */
+				/* T = IS_NOT_EQUAL(X, FALSE) => T = BOOL(X) */
+				/* Optimization of comparison with "null" is not safe,
+				 * because ("0" == null) is not equal to !("0")
+				 */
 				opline->opcode =
 					((opline->opcode != ZEND_IS_NOT_EQUAL) == ((Z_TYPE(ZEND_OP2_LITERAL(opline))) == IS_TRUE)) ?
 					ZEND_BOOL : ZEND_BOOL_NOT;