[MERGE #4831 @MikeHolman] Improve JSON.stringify perf for TypedArrays

Merge pull request #4831 from MikeHolman:arrenum During enumeration, we can (and should) avoid creating PropertyRecords for TypedArrays. Instead we can use the numeric index. In the below micro-benchmark, this improves our perf by about 45%. ```` const view = new Int8Array(1 << 24); for (let i = 0; i < view.length; ++i) { view[i] = i|0; } var start = Date.now(); const str = JSON.stringify(view); console.log(Date.now() - start); ```` OS: 16385822
chakra-core · Mar 19, 2018 · db575b6 · db575b6
2 parents 5f138a2 + 1e918e2
commit db575b6
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Showing 6 changed files with 71 additions and 30 deletions.
diff --git a/lib/Runtime/Library/JSONStringifier.cpp b/lib/Runtime/Library/JSONStringifier.cpp
@@ -198,7 +198,6 @@ JSONStringifier::Stringify(_In_ ScriptContext* scriptContext, _In_ Var value, _I
         wrapper,
         prop,
         value,
-        scriptContext->GetThreadContext()->GetEmptyStringPropertyRecord(),
         &objStack);
 
     if (prop->type == JSONContentType::Undefined)
@@ -340,7 +339,7 @@ JSONStringifier::ReadArrayElement(uint32 index, _In_ RecyclableObject* arr, _Out
         JavascriptOperators::GetItem(arr, index, &value, this->scriptContext);
     }
     JavascriptString* indexString = this->scriptContext->GetIntegerString(index);
-    this->ReadProperty(indexString, arr, prop, value, nullptr, objectStack);
+    this->ReadProperty(indexString, arr, prop, value, objectStack);
 }
 
 JSONArray*
@@ -386,19 +385,13 @@ JSONStringifier::ReadArray(_In_ RecyclableObject* arr, _In_ JSONObjectStack* obj
 }
 
 void
-JSONStringifier::ReadObjectElement(
+JSONStringifier::AppendObjectElement(
     _In_ JavascriptString* propertyName,
-    _In_opt_ PropertyRecord const* propertyRecord,
-    _In_ RecyclableObject* obj,
     _In_ JSONObject* jsonObject,
-    _In_ JSONObjectStack* objectStack)
+    _In_ JSONObjectProperty* prop)
 {
-    JSONObjectProperty prop;
-    prop.propertyName = propertyName;
-    this->ReadProperty(propertyName, obj, &prop.propertyValue, nullptr, propertyRecord, objectStack);
-
     // Undefined result is not concatenated
-    if (prop.propertyValue.type != JSONContentType::Undefined)
+    if (prop->propertyValue.type != JSONContentType::Undefined)
     {
         // Increase length for the name of the property
         this->totalStringLength = UInt32Math::Add(this->totalStringLength, CalculateStringElementLength(propertyName));
@@ -409,10 +402,47 @@ JSONStringifier::ReadObjectElement(
             // If gap is specified, a space is appended
             UInt32Math::Inc(this->totalStringLength);
         }
-        jsonObject->Push(prop);
+
+        jsonObject->Push(*prop);
     }
 }
 
+void
+JSONStringifier::ReadObjectElement(
+    _In_ JavascriptString* propertyName,
+    _In_ uint32 numericIndex,
+    _In_ RecyclableObject* obj,
+    _In_ JSONObject* jsonObject,
+    _In_ JSONObjectStack* objectStack)
+{
+    JSONObjectProperty prop;
+    prop.propertyName = propertyName;
+
+    Var value = JavascriptOperators::GetItem(obj, numericIndex, this->scriptContext);
+
+    this->ReadProperty(propertyName, obj, &prop.propertyValue, value, objectStack);
+
+    this->AppendObjectElement(propertyName, jsonObject, &prop);
+}
+
+void
+JSONStringifier::ReadObjectElement(
+    _In_ JavascriptString* propertyName,
+    _In_opt_ PropertyRecord const* propertyRecord,
+    _In_ RecyclableObject* obj,
+    _In_ JSONObject* jsonObject,
+    _In_ JSONObjectStack* objectStack)
+{
+    JSONObjectProperty prop;
+    prop.propertyName = propertyName;
+
+    Var value = this->ReadValue(propertyName, propertyRecord, obj);
+
+    this->ReadProperty(propertyName, obj, &prop.propertyValue, value, objectStack);
+
+    this->AppendObjectElement(propertyName, jsonObject, &prop);
+}
+
 // Calculates how many additional characters are needed for printing the Object/Array structure
 // This includes commas, brackets, and gap (if any)
 void
@@ -520,18 +550,25 @@ JSONStringifier::ReadObject(_In_ RecyclableObject* obj, _In_ JSONObjectStack* ob
             JavascriptStaticEnumerator enumerator;
             if (obj->GetEnumerator(&enumerator, EnumeratorFlags::SnapShotSemantics | EnumeratorFlags::EphemeralReference, this->scriptContext))
             {
-                enumerator.GetInitialPropertyCount();
                 JavascriptString* propertyName = nullptr;
                 PropertyId nextKey = Constants::NoProperty;
                 while ((propertyName = enumerator.MoveAndGetNext(nextKey)) != nullptr)
                 {
-                    PropertyRecord const * propertyRecord = nullptr;
-                    if (nextKey == Constants::NoProperty)
+                    const uint32 numericIndex = enumerator.GetCurrentItemIndex();
+                    if (numericIndex != Constants::InvalidSourceIndex)
+                    {
+                        this->ReadObjectElement(propertyName, numericIndex, obj, jsonObject, &stack);
+                    }
+                    else
                     {
-                        this->scriptContext->GetOrAddPropertyRecord(propertyName, &propertyRecord);
-                        nextKey = propertyRecord->GetPropertyId();
+                        PropertyRecord const * propertyRecord = nullptr;
+                        if (nextKey == Constants::NoProperty)
+                        {
+                            this->scriptContext->GetOrAddPropertyRecord(propertyName, &propertyRecord);
+                            nextKey = propertyRecord->GetPropertyId();
+                        }
+                        this->ReadObjectElement(propertyName, propertyRecord, obj, jsonObject, &stack);
                     }
-                    this->ReadObjectElement(propertyName, propertyRecord, obj, jsonObject, &stack);
                 }
             }
         }
@@ -728,17 +765,10 @@ JSONStringifier::ReadProperty(
     _In_ JavascriptString* key,
     _In_opt_ RecyclableObject* holder,
     _Out_ JSONProperty* prop,
-    _In_opt_ Var value,
-    _In_opt_ const PropertyRecord* propertyRecord,
+    _In_ Var value,
     _In_ JSONObjectStack* objectStack)
 {
     PROBE_STACK(this->scriptContext, Constants::MinStackDefault);
-    if (value == nullptr)
-    {
-        // If we don't have a value, we must have an object from which we can read it
-        AnalysisAssert(holder != nullptr);
-        value = this->ReadValue(key, propertyRecord, holder);
-    }
 
     // Save these to avoid having to recheck conditions unless value is modified by ToJSON or a replacer function
     RecyclableObject* valueObj = JavascriptOperators::TryFromVar<RecyclableObject>(value);

diff --git a/lib/Runtime/Library/JSONStringifier.h b/lib/Runtime/Library/JSONStringifier.h
@@ -63,6 +63,18 @@ class JSONStringifier
     uint32 ReadArrayLength(_In_ RecyclableObject* value);
     JSONArray* ReadArray(_In_ RecyclableObject* arr, _In_ JSONObjectStack* objectStack);
 
+    void AppendObjectElement(
+        _In_ JavascriptString* propertyName,
+        _In_ JSONObject* jsonObject,
+        _In_ JSONObjectProperty* prop);
+
+    void ReadObjectElement(
+        _In_ JavascriptString* propertyName,
+        _In_ uint32 numericIndex,
+        _In_ RecyclableObject* obj,
+        _In_ JSONObject* jsonObject,
+        _In_ JSONObjectStack* objectStack);
+
     void ReadObjectElement(
         _In_ JavascriptString* propertyName,
         _In_opt_ PropertyRecord const* propertyRecord,
@@ -95,8 +107,7 @@ class JSONStringifier
         _In_ JavascriptString* key,
         _In_opt_ RecyclableObject* holder,
         _Out_ JSONProperty* prop,
-        _In_opt_ Var value,
-        _In_opt_ const PropertyRecord* propertyRecord,
+        _In_ Var value,
         _In_ JSONObjectStack* objectStack);
 
     const char16* GetGap() const { return this->gap; };

diff --git a/lib/Runtime/Library/JavascriptStringEnumerator.h b/lib/Runtime/Library/JavascriptStringEnumerator.h
@@ -18,5 +18,6 @@ namespace Js
         JavascriptStringEnumerator(JavascriptString* stringObject, ScriptContext * requestContext);
         virtual void Reset() override;
         virtual JavascriptString * MoveAndGetNext(PropertyId& propertyId, PropertyAttributes* attributes = nullptr) override;
+        virtual uint32 GetCurrentItemIndex()  override { return index; }
     };
 }
diff --git a/lib/Runtime/Library/TypedArrayIndexEnumerator.h b/lib/Runtime/Library/TypedArrayIndexEnumerator.h
@@ -21,5 +21,6 @@ namespace Js
         TypedArrayIndexEnumerator(TypedArrayBase* typeArrayBase, EnumeratorFlags flags, ScriptContext* scriptContext);
         virtual JavascriptString * MoveAndGetNext(PropertyId& propertyId, PropertyAttributes* attributes = nullptr) override;
         virtual void Reset() override;
+        virtual uint32 GetCurrentItemIndex()  override { return index; }
     };
 }
diff --git a/lib/Runtime/Types/DynamicObjectPropertyEnumerator.h b/lib/Runtime/Types/DynamicObjectPropertyEnumerator.h
@@ -46,7 +46,6 @@ namespace Js
         bool GetSnapShotSemantics() const;
         bool GetUseCache() const;
         ScriptContext * GetScriptContext() const { return scriptContext; }
-        BigPropertyIndex GetInitialPropertyCount() const { return this->initialPropertyCount; }
 
         bool Initialize(DynamicObject * object, EnumeratorFlags flags, ScriptContext * requestContext, ForInCache * forInCache);
         bool IsNullEnumerator() const;

diff --git a/lib/Runtime/Types/JavascriptStaticEnumerator.h b/lib/Runtime/Types/JavascriptStaticEnumerator.h
@@ -39,7 +39,6 @@ namespace Js
         void Reset();
         uint32 GetCurrentItemIndex();
         JavascriptString * MoveAndGetNext(PropertyId& propertyId, PropertyAttributes* attributes = nullptr);
-        BigPropertyIndex GetInitialPropertyCount() const { return this->propertyEnumerator.GetInitialPropertyCount(); }
 
         static uint32 GetOffsetOfCurrentEnumerator() { return offsetof(JavascriptStaticEnumerator, currentEnumerator); }
         static uint32 GetOffsetOfPrefixEnumerator() { return offsetof(JavascriptStaticEnumerator, prefixEnumerator); }