From 375025f95c95c49e23df523ccee9e855d5de22a3 Mon Sep 17 00:00:00 2001
From: "Nicolas B. Pierron" <nicolas.b.pierron@mozilla.com>
Date: Thu, 26 Feb 2015 16:18:41 +0100
Subject: [PATCH] Bug 1129313 - Scalar Replacement: Remove PostWriteBarrier at
 the same time as the stores. r=h4writer

---
 js/src/jit/ScalarReplacement.cpp | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/js/src/jit/ScalarReplacement.cpp b/js/src/jit/ScalarReplacement.cpp
index 6a82c13bc8a..6db4b160727 100644
--- a/js/src/jit/ScalarReplacement.cpp
+++ b/js/src/jit/ScalarReplacement.cpp
@@ -143,6 +143,9 @@ IsObjectEscaped(MInstruction *ins, JSObject *objDefault = nullptr)
             JitSpewDef(JitSpew_Escape, "  is escaped by\n", def);
             return true;
 
+          case MDefinition::Op_PostWriteBarrier:
+            break;
+
           case MDefinition::Op_Slots: {
 #ifdef DEBUG
             // Assert that MSlots are only used by MStoreSlot and MLoadSlot.
@@ -245,6 +248,7 @@ class ObjectMemoryView : public MDefinitionVisitorDefaultNoop
     void visitObjectState(MObjectState *ins);
     void visitStoreFixedSlot(MStoreFixedSlot *ins);
     void visitLoadFixedSlot(MLoadFixedSlot *ins);
+    void visitPostWriteBarrier(MPostWriteBarrier *ins);
     void visitStoreSlot(MStoreSlot *ins);
     void visitLoadSlot(MLoadSlot *ins);
     void visitGuardShape(MGuardShape *ins);
@@ -451,6 +455,17 @@ ObjectMemoryView::visitLoadFixedSlot(MLoadFixedSlot *ins)
     ins->block()->discard(ins);
 }
 
+void
+ObjectMemoryView::visitPostWriteBarrier(MPostWriteBarrier *ins)
+{
+    // Skip loads made on other objects.
+    if (ins->object() != obj_)
+        return;
+
+    // Remove original instruction.
+    ins->block()->discard(ins);
+}
+
 void
 ObjectMemoryView::visitStoreSlot(MStoreSlot *ins)
 {