Only run slow path for VMEntryScope when globalObject changes

Jarred-Sumner · May 27, 2022 · e63c5d1 · e63c5d1
1 parent 72193e1
commit e63c5d1
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Showing 3 changed files with 19 additions and 2 deletions.
diff --git a/Source/JavaScriptCore/runtime/VM.h b/Source/JavaScriptCore/runtime/VM.h
@@ -931,6 +931,9 @@ class VM : public ThreadSafeRefCounted<VM>, public DoublyLinkedListNode<VM> {
 
 public:
     bool didEnterVM { false };
+    #if ENABLE(SINGLE_THREADED_VM_ENTRY_SCOPE)
+        void *entryScopeID { nullptr };
+    #endif
 private:
     bool m_failNextNewCodeBlock { false };
     bool m_globalConstRedeclarationShouldThrow { true };

diff --git a/Source/JavaScriptCore/runtime/VMEntryScope.cpp b/Source/JavaScriptCore/runtime/VMEntryScope.cpp
@@ -36,13 +36,18 @@
 
 namespace JSC {
 
+
 VMEntryScope::VMEntryScope(VM& vm, JSGlobalObject* globalObject)
     : m_vm(vm)
     , m_globalObject(globalObject)
 {
     if (!vm.entryScope) {
         vm.entryScope = this;
 
+#if ENABLE(SINGLE_THREADED_VM_ENTRY_SCOPE)
+        if (vm.entryScopeID != reinterpret_cast<void*>(globalObject)) {
+            vm.entryScopeID = globalObject;
+#endif
 #if ENABLE(WEBASSEMBLY)
         if (Wasm::isSupported())
             Wasm::startTrackingCurrentThread();
@@ -70,6 +75,9 @@ VMEntryScope::VMEntryScope(VM& vm, JSGlobalObject* globalObject)
 #endif
         if (UNLIKELY(Options::useTracePoints()))
             tracePoint(VMEntryScopeStart);
+        #if ENABLE(SINGLE_THREADED_VM_ENTRY_SCOPE)
+        }
+        #endif
     }
 
     vm.clearLastException();

diff --git a/Source/cmake/OptionsJSCOnly.cmake b/Source/cmake/OptionsJSCOnly.cmake
@@ -53,10 +53,16 @@ if (ENABLE_REMOTE_INSPECTOR)
 else (
     set(ENABLE_INSPECTOR_ALTERNATE_DISPATCHERS OFF)
 )
-
 endif ()
+WEBKIT_OPTION_END()
 
-
+WEBKIT_OPTION_BEGIN()
+WEBKIT_OPTION_DEFINE(ENABLE_SINGLE_THREADED_VM_ENTRY_SCOPE "Only set VMEntryScope once per globalobject" PUBLIC OFF)
+if (ENABLE_SINGLE_THREADED_VM_ENTRY_SCOPE)
+    set(ENABLE_SINGLE_THREADED_VM_ENTRY_SCOPE ON)
+    SET_AND_EXPOSE_TO_BUILD(ENABLE_SINGLE_THREADED_VM_ENTRY_SCOPE 1)
+endif ()
+WEBKIT_OPTION_END()
 
 if (WIN32)
     set(ENABLE_API_TESTS OFF)