Changeset 284715 in webkit

Timestamp:

Oct 22, 2021, 2:47:34 PM (5 years ago)

Author:

mark.lam@apple.com

Message:

Change Heap::writeBarrier() to do the cheaper check first.
​https://bugs.webkit.org/show_bug.cgi?id=232172

Reviewed by Robin Morisset.

It's cheaper to do a check using incoming args (which are already loaded in
registers) than to do a check which requires memory loads.

• heap/HeapInlines.h:

(JSC::Heap::writeBarrier):

Location:

trunk/Source/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• heap/HeapInlines.h (modified) (1 diff)

trunk/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+2021-10-22  Mark Lam  <mark.lam@apple.com>
+
+        Change Heap::writeBarrier() to do the cheaper check first.
+        https://bugs.webkit.org/show_bug.cgi?id=232172
+
+        Reviewed by Robin Morisset.
+
+        It's cheaper to do a check using incoming args (which are already loaded in
+        registers) than to do a check which requires memory loads.
+
+        * heap/HeapInlines.h:
+        (JSC::Heap::writeBarrier):
+
 2021-10-22  Asumu Takikawa  <asumu@igalia.com>
 

trunk/Source/JavaScriptCore/heap/HeapInlines.h

@@ -110 +110 @@
     if (!from)
         return;
+    if (LIKELY(!to))
+        return;
     if (!isWithinThreshold(from->cellState(), barrierThreshold()))
-        return;
-    if (LIKELY(!to))
         return;
     writeBarrierSlowPath(from);