Changeset 36317 in webkit for trunk/JavaScriptCore/VM/Machine.cpp

Timestamp:

Sep 10, 2008, 2:23:35 AM (17 years ago)

Author:

[email protected]

Message:

Add optimised access to known properties on the global object.

Reviewed by Maciej Stachowiak

Improve cross scope access to the global object by emitting
code to access it directly rather than by walking the scope chain.

This is a 0.8% win in SunSpider and a 1.7% win in the v8 benchmarks.

File:

• trunk/JavaScriptCore/VM/Machine.cpp (modified) (1 diff)

trunk/JavaScriptCore/VM/Machine.cpp

@@ -2087 +2087 @@
         NEXT_OPCODE;
     }
+    BEGIN_OPCODE(op_get_global_var) {
+        /* get_global_var dst(r) index(n)
+
+           Gets the global var at global slot index and places it in register dst.
+         */
+        int dst = (++vPC)->u.operand;
+        JSGlobalObject* scope = static_cast<JSGlobalObject*>((++vPC)->u.jsCell);
+        ASSERT(scope->isGlobalObject());
+        int index = (++vPC)->u.operand;
+
+        r[dst] = scope->registerAt(index);
+        ++vPC;
+        NEXT_OPCODE;
+    }
+    BEGIN_OPCODE(op_put_global_var) {
+        /* put_global_var globalObject(c) index(n) value(r)
+         
+           Puts value into global slot index.
+         */
+        JSGlobalObject* scope = static_cast<JSGlobalObject*>((++vPC)->u.jsCell);
+        ASSERT(scope->isGlobalObject());
+        int index = (++vPC)->u.operand;
+        int value = (++vPC)->u.operand;
+        
+        scope->registerAt(index) = r[value].jsValue(exec);
+        ++vPC;
+        NEXT_OPCODE;
+    }            
     BEGIN_OPCODE(op_get_scoped_var) {
         /* get_scoped_var dst(r) index(n) skip(n)