opcache: fix PASS_15 constant inlining correctness

- define() must not be inlined; it works at runtime. Record a sentinel to also block inlining of any subsequent const redeclaration of the same name.
- Attributed constants must not be inlined; attributes like #[\Deprecated] need to fire at access time, which inlining bypasses.
  Same sentinel approach blocks subsequent redeclarations.

Extract sentinel logic into zend_optimizer_block_constant().

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) &&
@@ -287,6 +292,12 @@ void zend_optimizer_pass1(zend_op_array *op_array, zend_optimizer_ctx *ctx)
 			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_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/const_inline_define.phpt

@@ -1,5 +1,5 @@
 --TEST--
-const and define() at file scope are inlined by the optimizer
+const at file scope is inlined by the optimizer, define() is not
 --EXTENSIONS--
 opcache
 --INI--
@@ -39,4 +39,5 @@ use_define:
      ; (lines=%d, args=%d, vars=%d, tmps=%d)
      ; (after optimizer)
      ; %s
-0000 RETURN int(2)
+0000 T%d = FETCH_CONSTANT string("DEFINE_VAL")
+0001 RETURN %s