Fix performace regression due to missed peephole optimization

src/codegen-ia32.cc

Index: src/codegen-ia32.cc
===================================================================
--- src/codegen-ia32.cc	(revision 282)
+++ src/codegen-ia32.cc	(working copy)
@@ -975,6 +975,7 @@
     ASSERT(var()->mode() != Variable::DYNAMIC);
 
     Label exit;
+    bool skipped_write = false;
     if (init_state == CONST_INIT) {
       ASSERT(var()->mode() == Variable::CONST);
       // Only the first const initialization must be executed (the slot
@@ -984,6 +985,7 @@
       masm->mov(eax, Ia32CodeGenerator::SlotOperand(masm, scope, this, ecx));
       masm->cmp(eax, Factory::the_hole_value());
       masm->j(not_equal, &exit);
+      skipped_write = true;
     }
 
     // We must execute the store.
@@ -1003,7 +1005,9 @@
       int offset = FixedArray::kHeaderSize + index() * kPointerSize;
       masm->RecordWrite(ecx, offset, eax, ebx);
     }
-    masm->bind(&exit);
+    // If we did not jump over the assignment, we do not need to bind the
+    // exit label.  Doing so can defeat peephole optimization.
+    if (skipped_write) masm->bind(&exit);
   }
 }