jscript: Create the source function's 'prototype' prop object on demand.

The 'prototype' prop of a source function is, by default, an empty object with a 'constructor' prop pointing back to the function. Currently, every source function is created in this fashion, which makes it a circular reference and thus prevents it from being freed until the Garbage Collector kicks in. The performance impact comes from the function keeping a ref to the enclosing scope, and since the scope is being held by it, the engine will detach the scope, believing it to be used for the time being (until the GC cleans it). This can cause substantial performance issues for such a common case. The FFXIV Launcher, for example, leaks a large amount of such short-lived functions and the enclosing scopes. Signed-off-by: Gabriel Ivăncescu <gabrielopcode@gmail.com>

jscript: Create the source function's 'prototype' prop object on demand.
27ceb62e · Gabriel Ivăncescu · Alexandre Julliard · d192aa10 · 27ceb62e
Commit 27ceb62e authored Dec 08, 2022 by Gabriel Ivăncescu Committed by Alexandre Julliard Dec 08, 2022
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function.c dlls/jscript/function.c +51 -16

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--- a/dlls/jscript/function.c
+++ b/dlls/jscript/function.c
@@ -756,6 +756,55 @@ HRESULT create_builtin_constructor(script_ctx_t *ctx, builtin_invoke_t value_pro
    return S_OK;
 }
+/*
+ * Create the actual prototype on demand, since it is a circular ref, which prevents the vast
+ * majority of functions from being released quickly, leading to unnecessary scope detach.
+ */
+static HRESULT InterpretedFunction_get_prototype(script_ctx_t *ctx, jsdisp_t *jsthis, jsval_t *r)
+{
+    jsdisp_t *prototype;
+    HRESULT hres;
+    hres = create_object(ctx, NULL, &prototype);
+    if(FAILED(hres))
+        return hres;
+    hres = jsdisp_define_data_property(jsthis, L"prototype", PROPF_WRITABLE, jsval_obj(prototype));
+    if(SUCCEEDED(hres))
+        hres = set_constructor_prop(ctx, jsthis, prototype);
+    if(FAILED(hres)) {
+        jsdisp_release(prototype);
+        return hres;
+    }
+    *r = jsval_obj(prototype);
+    return S_OK;
+}
+static HRESULT InterpretedFunction_set_prototype(script_ctx_t *ctx, jsdisp_t *jsthis, jsval_t value)
+{
+    return jsdisp_define_data_property(jsthis, L"prototype", PROPF_WRITABLE, value);
+}
+static const builtin_prop_t InterpretedFunction_props[] = {
+    {L"arguments",           NULL, 0,                        Function_get_arguments},
+    {L"length",              NULL, 0,                        Function_get_length},
+    {L"prototype",           NULL, 0,                        InterpretedFunction_get_prototype, InterpretedFunction_set_prototype}
+};
+static const builtin_info_t InterpretedFunction_info = {
+    JSCLASS_FUNCTION,
+    Function_value,
+    ARRAY_SIZE(InterpretedFunction_props),
+    InterpretedFunction_props,
+    Function_destructor,
+    NULL,
+    NULL,
+    NULL,
+    NULL,
+    Function_gc_traverse
+};
 static HRESULT InterpretedFunction_call(script_ctx_t *ctx, FunctionInstance *func, jsval_t vthis, unsigned flags,
         unsigned argc, jsval_t *argv, jsval_t *r)
 {
@@ -838,24 +887,10 @@ HRESULT create_source_function(script_ctx_t *ctx, bytecode_t *code, function_cod
        scope_chain_t *scope_chain, jsdisp_t **ret)
 {
    InterpretedFunction *function;
-    jsdisp_t *prototype;
    HRESULT hres;
-    hres = create_object(ctx, NULL, &prototype);
+    hres = create_function(ctx, &InterpretedFunction_info, &InterpretedFunctionVtbl, sizeof(InterpretedFunction),
-    if(FAILED(hres))
+                           PROPF_CONSTR, FALSE, NULL, (void**)&function);
-        return hres;
-    hres = create_function(ctx, NULL, &InterpretedFunctionVtbl, sizeof(InterpretedFunction), PROPF_CONSTR,
-                           FALSE, NULL, (void**)&function);
-    if(SUCCEEDED(hres)) {
-        hres = jsdisp_define_data_property(&function->function.dispex, L"prototype", PROPF_WRITABLE,
-                                           jsval_obj(prototype));
-        if(SUCCEEDED(hres))
-            hres = set_constructor_prop(ctx, &function->function.dispex, prototype);
-        if(FAILED(hres))
-            jsdisp_release(&function->function.dispex);
-    }
-    jsdisp_release(prototype);
    if(FAILED(hres))
        return hres;