Changeset 50254 in webkit for trunk/JavaScriptCore/parser/Nodes.cpp

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/parser/Nodes.cpp (modified) (4 diffs)

trunk/JavaScriptCore/parser/Nodes.cpp

@@ -1478 +1478 @@
     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());
@@ -1485 +1486 @@
 
     RegisterID* propertyName;
+    bool optimizedForinAccess = false;
     if (m_lexpr->isResolveNode()) {
         const Identifier& ident = static_cast<ResolveNode*>(m_lexpr)->identifier();
@@ -1495 +1497 @@
             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()) {
@@ -1518 +1524 @@
 
     generator.emitNode(dst, m_statement);
+
+    if (optimizedForinAccess)
+        generator.popOptimisedForIn();
 
     generator.emitLabel(scope->continueTarget());