Generate lookups into the global object more aggressively

Since change 9333ea8649838d7e0400b0e94c8cbd4fa5d216b0, we lookup
properties in the QML context object before the global object to
have proper scoping rules for QML.

Unfortunately this lead to a performance regression when using global
properties such as Math in imported script files, as the lookup would
always go through the qml context first.

This can be fixed, as we know that the global object is frozen in qml
mode, and the standard names of properties in the global object are
illegal to use in QML. So simply check for those names in the code
generator and create lookups into the global object for those.

Change-Id: I4b2089178c9e5f9440abdfd834cf7d92c3c0e2c3
Fixes: QTBUG-71591
Reviewed-by: Erik Verbruggen <erik.verbruggen@qt.io>

1 files changed, 70 insertions, 0 deletions

diff --git a/src/qml/compiler/qv4codegen.cpp b/src/qml/compiler/qv4codegen.cpp
index 54aef16970..21fb03c1a4 100644
--- a/src/qml/compiler/qv4codegen.cpp
+++ b/src/qml/compiler/qv4codegen.cpp
@@ -102,6 +102,62 @@ Codegen::Codegen(QV4::Compiler::JSUnitGenerator *jsUnitGenerator, bool strict)
     jsUnitGenerator->codeGeneratorName = QStringLiteral("moth");
 }
 
+const char *globalNames[] = {
+    "isNaN",
+    "parseFloat",
+    "String",
+    "EvalError",
+    "URIError",
+    "Math",
+    "encodeURIComponent",
+    "RangeError",
+    "eval",
+    "isFinite",
+    "ReferenceError",
+    "Infinity",
+    "Function",
+    "RegExp",
+    "Number",
+    "parseInt",
+    "Object",
+    "decodeURI",
+    "TypeError",
+    "Boolean",
+    "encodeURI",
+    "NaN",
+    "Error",
+    "decodeURIComponent",
+    "Date",
+    "Array",
+    "Symbol",
+    "escape",
+    "unescape",
+    "SyntaxError",
+    "undefined",
+    "JSON",
+    "ArrayBuffer",
+    "SharedArrayBuffer",
+    "DataView",
+    "Int8Array",
+    "Uint8Array",
+    "Uint8ClampedArray",
+    "Int16Array",
+    "Uint16Array",
+    "Int32Array",
+    "Uint32Array",
+    "Float32Array",
+    "Float64Array",
+    "WeakSet",
+    "Set",
+    "WeakMap",
+    "Map",
+    "Reflect",
+    "Proxy",
+    "Atomics",
+    "Promise",
+    nullptr
+};
+
 void Codegen::generateFromProgram(const QString &fileName,
                                   const QString &finalUrl,
                                   const QString &sourceCode,
@@ -118,6 +174,18 @@ void Codegen::generateFromProgram(const QString &fileName,
     _module->fileName = fileName;
     _module->finalUrl = finalUrl;
 
+    if (contextType == ContextType::ScriptImportedByQML) {
+        // the global object is frozen, so we know that members of it are
+        // pointing to the global object. This is important so that references
+        // to Math etc. do not go through the expensive path in the context wrapper
+        // that tries to see whether we have a matching type
+        //
+        // Since this can be called from the loader thread we can't get the list
+        // directly from the engine, so let's hardcode the most important ones here
+        for (const char **g = globalNames; *g != nullptr; ++g)
+            m_globalNames << QString::fromLatin1(*g);
+    }
+
     ScanFunctions scan(this, sourceCode, contextType);
     scan(node);
 
@@ -2350,6 +2418,8 @@ Codegen::Reference Codegen::referenceForName(const QString &name, bool isLhs, co
 
     Reference r = Reference::fromName(this, name);
     r.global = useFastLookups && (resolved.type == Context::ResolvedName::Global);
+    if (!r.global && m_globalNames.contains(name))
+        r.global = true;
     return r;
 }