commit baca5e860ba9e25df98c9d6eb10a225931f7e4a6
author akling@apple.com <akling@apple.com@268f45cc-cd09-0410-ab3c-d52691b4dbfc> Tue May 06 00:53:29 2014 +0000
committer akling@apple.com <akling@apple.com@268f45cc-cd09-0410-ab3c-d52691b4dbfc> Tue May 06 00:53:29 2014 +0000
tree cffd55485792e898dff0bcc1bf7f328612aba54b
parent 02f2d81fbb769accbfa1c06f7a6ffcf2c578cf9f

Optimize GetByVal when subscript is a rope string.
<https://webkit.org/b/132590>

Use JSString::toIdentifier() in the various GetByVal implementations
to try and avoid allocating extra strings.

Added canUseFastGetOwnProperty() and wrap calls to fastGetOwnProperty()
in that, to avoid calling JSString::value() which always resolves ropes
into new strings and de-optimizes subsequent toIdentifier() calls.

My iMac says ~9% progression on Dromaeo/dom-attr.html

Reviewed by Phil Pizlo.

* dfg/DFGOperations.cpp:
* jit/JITOperations.cpp:
(JSC::getByVal):
* llint/LLIntSlowPaths.cpp:
(JSC::LLInt::getByVal):
* runtime/JSCell.h:
* runtime/JSCellInlines.h:
(JSC::JSCell::fastGetOwnProperty):
(JSC::JSCell::canUseFastGetOwnProperty):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@168335 268f45cc-cd09-0410-ab3c-d52691b4dbfc

Source/JavaScriptCore/dfg/DFGOperations.cpp

diff --git a/Source/JavaScriptCore/dfg/DFGOperations.cpp b/Source/JavaScriptCore/dfg/DFGOperations.cpp
index 8c9ab40..99a8725 100644
--- a/Source/JavaScriptCore/dfg/DFGOperations.cpp
+++ b/Source/JavaScriptCore/dfg/DFGOperations.cpp
@@ -295,15 +295,18 @@
             if (propertyAsUInt32 == propertyAsDouble)
                 return getByVal(exec, base, propertyAsUInt32);
         } else if (property.isString()) {
-            if (JSValue result = base->fastGetOwnProperty(vm, asString(property)->value(exec)))
-                return JSValue::encode(result);
+            Structure& structure = *base->structure(vm);
+            if (JSCell::canUseFastGetOwnProperty(structure)) {
+                if (JSValue result = base->fastGetOwnProperty(vm, structure, asString(property)->value(exec)))
+                    return JSValue::encode(result);
+            }
         }
     }
 
     if (isName(property))
         return JSValue::encode(baseValue.get(exec, jsCast<NameInstance*>(property.asCell())->privateName()));
 
-    Identifier ident(exec, property.toString(exec)->value(exec));
+    Identifier ident = property.toString(exec)->toIdentifier(exec);
     return JSValue::encode(baseValue.get(exec, ident));
 }
 
@@ -322,14 +325,17 @@
         if (propertyAsUInt32 == propertyAsDouble)
             return getByVal(exec, base, propertyAsUInt32);
     } else if (property.isString()) {
-        if (JSValue result = base->fastGetOwnProperty(vm, asString(property)->value(exec)))
-            return JSValue::encode(result);
+        Structure& structure = *base->structure(vm);
+        if (JSCell::canUseFastGetOwnProperty(structure)) {
+            if (JSValue result = base->fastGetOwnProperty(vm, structure, asString(property)->value(exec)))
+                return JSValue::encode(result);
+        }
     }
 
     if (isName(property))
         return JSValue::encode(JSValue(base).get(exec, jsCast<NameInstance*>(property.asCell())->privateName()));
 
-    Identifier ident(exec, property.toString(exec)->value(exec));
+    Identifier ident = property.toString(exec)->toIdentifier(exec);
     return JSValue::encode(JSValue(base).get(exec, ident));
 }