1 files changed, 16 insertions, 5 deletions
diff --git a/JavaScriptCore/parser/Nodes.cpp b/JavaScriptCore/parser/Nodes.cpp
index 3bd318a..45009dc 100644
--- a/JavaScriptCore/parser/Nodes.cpp
+++ b/JavaScriptCore/parser/Nodes.cpp
@@ -1468,20 +1468,24 @@ RegisterID* ForInNode::emitBytecode(BytecodeGenerator& generator, RegisterID* ds
     if (!m_lexpr->isLocation())
         return emitThrowError(generator, ReferenceError, "Left side of for-in statement is not a reference.");
 
-    RefPtr<Label> continueTarget = generator.newLabel(); 
-
     generator.emitDebugHook(WillExecuteStatement, firstLine(), lastLine());
 
     if (m_init)
         generator.emitNode(generator.ignoredResult(), m_init);
-    RegisterID* forInBase = generator.emitNode(m_expr);
-    RefPtr<RegisterID> iter = generator.emitGetPropertyNames(generator.newTemporary(), forInBase);
+
+    RefPtr<RegisterID> base = generator.newTemporary();
+    generator.emitNode(base.get(), m_expr);
+    RefPtr<RegisterID> i = generator.newTemporary();
+    RefPtr<RegisterID> size = generator.newTemporary();
+    RefPtr<RegisterID> expectedSubscript;
+    RefPtr<RegisterID> iter = generator.emitGetPropertyNames(generator.newTemporary(), base.get(), i.get(), size.get(), scope->breakTarget());
     generator.emitJump(scope->continueTarget());
 
     RefPtr<Label> loopStart = generator.newLabel();
     generator.emitLabel(loopStart.get());
 
     RegisterID* propertyName;
+    bool optimizedForinAccess = false;
     if (m_lexpr->isResolveNode()) {
         const Identifier& ident = static_cast<ResolveNode*>(m_lexpr)->identifier();
         propertyName = generator.registerFor(ident);
@@ -1492,6 +1496,10 @@ RegisterID* ForInNode::emitBytecode(BytecodeGenerator& generator, RegisterID* ds
 
             generator.emitExpressionInfo(divot(), startOffset(), endOffset());
             generator.emitPutById(base, ident, propertyName);
+        } else {
+            expectedSubscript = generator.emitMove(generator.newTemporary(), propertyName);
+            generator.pushOptimisedForIn(expectedSubscript.get(), iter.get(), i.get(), propertyName);
+            optimizedForinAccess = true;
         }
     } else if (m_lexpr->isDotAccessorNode()) {
         DotAccessorNode* assignNode = static_cast<DotAccessorNode*>(m_lexpr);
@@ -1516,8 +1524,11 @@ RegisterID* ForInNode::emitBytecode(BytecodeGenerator& generator, RegisterID* ds
 
     generator.emitNode(dst, m_statement);
 
+    if (optimizedForinAccess)
+        generator.popOptimisedForIn();
+
     generator.emitLabel(scope->continueTarget());
-    generator.emitNextPropertyName(propertyName, iter.get(), loopStart.get());
+    generator.emitNextPropertyName(propertyName, base.get(), i.get(), size.get(), iter.get(), loopStart.get());
     generator.emitDebugHook(WillExecuteStatement, firstLine(), lastLine());
     generator.emitLabel(scope->breakTarget());
     return dst;