opcache: re-enable PASS_15 (constant collection) by default

Disabled in Dec 2015 (940c68b, 4070279) to fix bug #71127.

define() and attributed constants are blocked from inlining via a
sentinel entry. define() can be overridden at runtime (bug #71127)
and attributed constants need to fire at access time. The sentinel
also prevents inlining of any subsequent const redeclaration of the
same name.

Adds zend_optimizer_block_constant() for sentinel logic.

Author: wilaak

Zend/Optimizer/pass1.c

@@ -151,6 +151,10 @@ void zend_optimizer_pass1(zend_op_array *op_array, zend_optimizer_ctx *ctx)
 					if (!ctx->constants || !zend_optimizer_get_collected_constant(ctx->constants, &ZEND_OP2_LITERAL(opline), &result)) {
 						break;
 					}
+					if (Z_TYPE(result) == IS_UNDEF) {
+						/* blocked by define() or attributed const */
+						break;
+					}
 				}
 				if (Z_TYPE(result) == IS_CONSTANT_AST) {
 					break;
@@ -224,8 +228,9 @@ void zend_optimizer_pass1(zend_op_array *op_array, zend_optimizer_ctx *ctx)
 
 				if (Z_TYPE(ZEND_OP1_LITERAL(send1_opline)) == IS_STRING && send2_opline) {
 
+					/* define() can be overridden at runtime; block inlining */
 					if (collect_constants) {
-						zend_optimizer_collect_constant(ctx, &ZEND_OP1_LITERAL(send1_opline), &ZEND_OP1_LITERAL(send2_opline));
+						zend_optimizer_block_constant(ctx, &ZEND_OP1_LITERAL(send1_opline));
 					}
 
 					if (RESULT_UNUSED(opline) &&
@@ -286,6 +291,13 @@ void zend_optimizer_pass1(zend_op_array *op_array, zend_optimizer_ctx *ctx)
 			literal_dtor(&ZEND_OP1_LITERAL(opline));
 			replace_by_const_or_qm_assign(op_array, opline, &result);
 			break;
+		case ZEND_DECLARE_ATTRIBUTED_CONST:
+			/* attributes must fire at access time; block inlining */
+			if (collect_constants &&
+			    Z_TYPE(ZEND_OP1_LITERAL(opline)) == IS_STRING) {
+				zend_optimizer_block_constant(ctx, &ZEND_OP1_LITERAL(opline));
+			}
+			break;
 		case ZEND_DECLARE_CONST:
 			if (collect_constants &&
 			    Z_TYPE(ZEND_OP1_LITERAL(opline)) == IS_STRING &&

Zend/Optimizer/zend_optimizer.c

@@ -51,6 +51,19 @@ void zend_optimizer_collect_constant(zend_optimizer_ctx *ctx, const zval *name,
 	}
 }
 
+/* prevent inlining of a constant; UNDEF sentinel blocks later DECLARE_CONST collection */
+void zend_optimizer_block_constant(zend_optimizer_ctx *ctx, const zval *name)
+{
+	if (!ctx->constants) {
+		ctx->constants = zend_arena_alloc(&ctx->arena, sizeof(HashTable));
+		zend_hash_init(ctx->constants, 16, NULL, zval_ptr_dtor_nogc, 0);
+	}
+
+	zval undef;
+	ZVAL_UNDEF(&undef);
+	zend_hash_add(ctx->constants, Z_STR_P(name), &undef);
+}
+
 zend_result zend_optimizer_eval_binary_op(zval *result, uint8_t opcode, zval *op1, zval *op2) /* {{{ */
 {
 	if (zend_binary_op_produces_error(opcode, op1, op2)) {

Zend/Optimizer/zend_optimizer.h

@@ -46,7 +46,7 @@
 
 #define ZEND_OPTIMIZER_ALL_PASSES	0x7FFFFFFF
 
-#define DEFAULT_OPTIMIZATION_LEVEL  "0x7FFEBFFF"
+#define DEFAULT_OPTIMIZATION_LEVEL  "0x7FFEFFFF"
 
 
 #define ZEND_DUMP_AFTER_PASS_1		ZEND_OPTIMIZER_PASS_1

Zend/Optimizer/zend_optimizer_internal.h

@@ -80,6 +80,7 @@ void zend_optimizer_convert_to_free_op1(const zend_op_array *op_array, zend_op *
 uint32_t zend_optimizer_add_literal(zend_op_array *op_array, const zval *zv);
 bool zend_optimizer_get_persistent_constant(zend_string *name, zval *result, bool copy);
 void zend_optimizer_collect_constant(zend_optimizer_ctx *ctx, const zval *name, zval* value);
+void zend_optimizer_block_constant(zend_optimizer_ctx *ctx, const zval *name);
 bool zend_optimizer_get_collected_constant(const HashTable *constants, const zval *name, zval* value);
 zend_result zend_optimizer_eval_binary_op(zval *result, uint8_t opcode, zval *op1, zval *op2);
 zend_result zend_optimizer_eval_unary_op(zval *result, uint8_t opcode, zval *op1);

ext/opcache/tests/pass1_const_inline_001.phpt

@@ -0,0 +1,43 @@
+--TEST--
+const at file scope is inlined by the optimizer, define() is not
+--EXTENSIONS--
+opcache
+--INI--
+opcache.enable_cli=1
+opcache.opt_debug_level=0x20000
+--FILE--
+<?php
+
+const CONST_VAL = 1;
+define('DEFINE_VAL', 2);
+
+function use_const() {
+    return CONST_VAL;
+}
+
+function use_define() {
+    return DEFINE_VAL;
+}
+
+?>
+--EXPECTF--
+$_main:
+     ; (lines=%d, args=%d, vars=%d, tmps=%d)
+     ; (after optimizer)
+     ; %s
+0000 DECLARE_CONST string("CONST_VAL") int(1)
+0001 DECLARE_CONST string("DEFINE_VAL") int(2)
+0002 RETURN int(1)
+
+use_const:
+     ; (lines=%d, args=%d, vars=%d, tmps=%d)
+     ; (after optimizer)
+     ; %s
+0000 RETURN int(1)
+
+use_define:
+     ; (lines=%d, args=%d, vars=%d, tmps=%d)
+     ; (after optimizer)
+     ; %s
+0000 T%d = FETCH_CONSTANT string("DEFINE_VAL")
+0001 RETURN %s

ext/opcache/tests/pass1_const_inline_002.phpt

@@ -0,0 +1,64 @@
+--TEST--
+Global and namespace const declarations are inlined by the optimizer
+--EXTENSIONS--
+opcache
+--INI--
+opcache.enable_cli=1
+opcache.opt_debug_level=0x20000
+--FILE--
+<?php
+
+const GLOBAL_CONST = 42;
+
+function use_global_const() {
+    return GLOBAL_CONST;
+}
+
+function use_global_const_fqn() {
+    return \GLOBAL_CONST;
+}
+
+class MyClass {
+    const CLASS_CONST = 99;
+
+    public function use_class_const() {
+        return self::CLASS_CONST;
+    }
+}
+
+function use_class_const_static() {
+    return MyClass::CLASS_CONST;
+}
+
+?>
+--EXPECTF--
+$_main:
+     ; (lines=%d, args=%d, vars=%d, tmps=%d)
+     ; (after optimizer)
+     ; %s
+0000 DECLARE_CONST string("GLOBAL_CONST") int(42)
+0001 RETURN int(1)
+
+use_global_const:
+     ; (lines=%d, args=%d, vars=%d, tmps=%d)
+     ; (after optimizer)
+     ; %s
+0000 RETURN int(42)
+
+use_global_const_fqn:
+     ; (lines=%d, args=%d, vars=%d, tmps=%d)
+     ; (after optimizer)
+     ; %s
+0000 RETURN int(42)
+
+use_class_const_static:
+     ; (lines=%d, args=%d, vars=%d, tmps=%d)
+     ; (after optimizer)
+     ; %s
+0000 RETURN int(99)
+
+MyClass::use_class_const:
+     ; (lines=%d, args=%d, vars=%d, tmps=%d)
+     ; (after optimizer)
+     ; %s
+0000 RETURN int(99)

ext/opcache/tests/pass1_const_inline_003.phpt

@@ -0,0 +1,41 @@
+--TEST--
+Namespace const declarations are inlined by the optimizer
+--EXTENSIONS--
+opcache
+--INI--
+opcache.enable_cli=1
+opcache.opt_debug_level=0x20000
+--FILE--
+<?php
+namespace MyNS;
+
+const NS_CONST = 100;
+
+function use_ns_const() {
+    return NS_CONST;
+}
+
+function use_ns_const_fqn() {
+    return \MyNS\NS_CONST;
+}
+
+?>
+--EXPECTF--
+$_main:
+     ; (lines=%d, args=%d, vars=%d, tmps=%d)
+     ; (after optimizer)
+     ; %s
+0000 DECLARE_CONST string("MyNS\\NS_CONST") int(100)
+0001 RETURN int(1)
+
+MyNS\use_ns_const:
+     ; (lines=%d, args=%d, vars=%d, tmps=%d)
+     ; (after optimizer)
+     ; %s
+0000 RETURN int(100)
+
+MyNS\use_ns_const_fqn:
+     ; (lines=%d, args=%d, vars=%d, tmps=%d)
+     ; (after optimizer)
+     ; %s
+0000 RETURN int(100)

ext/opcache/tests/pass1_const_inline_004.phpt

@@ -0,0 +1,22 @@
+--TEST--
+define() followed by const redeclaration is not inlined
+--EXTENSIONS--
+opcache
+--INI--
+opcache.enable_cli=1
+--FILE--
+<?php
+
+define('FOO', 'first');
+const FOO = 'second';
+
+function get_foo() {
+    return FOO;
+}
+
+var_dump(get_foo());
+
+?>
+--EXPECTF--
+Warning: Constant FOO already defined, this will be an error in PHP 9 in %s on line %d
+string(5) "first"