Changeset 50254 in webkit for trunk/JavaScriptCore/bytecompiler/BytecodeGenerator.h

Timestamp:

Oct 28, 2009, 6:25:02 PM (16 years ago)

Author:

[email protected]

Message:

Improve for..in enumeration performance
​https://bugs.webkit.org/show_bug.cgi?id=30887

Reviewed by Geoff Garen.

Improve indexing of an object with a for..in iterator by
identifying cases where get_by_val is being used with a iterator
as the subscript and replace it with a new get_by_pname
bytecode. get_by_pname then optimizes lookups that directly access
the base object.

File:

• trunk/JavaScriptCore/bytecompiler/BytecodeGenerator.h (modified) (3 diffs)

trunk/JavaScriptCore/bytecompiler/BytecodeGenerator.h

@@ -62 +62 @@
     };
 
+    struct ForInContext {
+        RefPtr<RegisterID> expectedSubscriptRegister;
+        RefPtr<RegisterID> iterRegister;
+        RefPtr<RegisterID> indexRegister;
+        RefPtr<RegisterID> propertyRegister;
+    };
+
     class BytecodeGenerator : public FastAllocBase {
     public:
@@ -332 +339 @@
         void popFinallyContext();
 
+        void pushOptimisedForIn(RegisterID* expectedBase, RegisterID* iter, RegisterID* index, RegisterID* propertyRegister)
+        {
+            ForInContext context = { expectedBase, iter, index, propertyRegister };
+            m_forInContextStack.append(context);
+        }
+
+        void popOptimisedForIn()
+        {
+            m_forInContextStack.removeLast();
+        }
+
         LabelScope* breakTarget(const Identifier&);
         LabelScope* continueTarget(const Identifier&);
@@ -468 +486 @@
         Vector<ControlFlowContext> m_scopeContextStack;
         Vector<SwitchInfo> m_switchContextStack;
+        Vector<ForInContext> m_forInContextStack;
 
         int m_nextGlobalIndex;