[hydrogen] don't bailout assignments to consts

src/ia32/lithium-codegen-ia32.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2153 matching lines @@
 void LCodeGen::DoLoadContextSlot(LLoadContextSlot* instr) {
   Register context = ToRegister(instr->context());
   Register result = ToRegister(instr->result());
   __ mov(result, ContextOperand(context, instr->slot_index()));
 }
 
 
 void LCodeGen::DoStoreContextSlot(LStoreContextSlot* instr) {
   Register context = ToRegister(instr->context());
   Register value = ToRegister(instr->value());
+
+  Label skip_assignment;
+
+  if (instr->RequiresHoleCheck()) {
+    __ cmp(ContextOperand(context, instr->slot_index()),
+           factory()->the_hole_value());
+    __ j(not_equal, &skip_assignment, Label::kNear);
+  }
+
   __ mov(ContextOperand(context, instr->slot_index()), value);
   if (instr->hydrogen()->NeedsWriteBarrier()) {
     HType type = instr->hydrogen()->value()->type();
     SmiCheck check_needed =
         type.IsHeapObject() ? OMIT_SMI_CHECK : INLINE_SMI_CHECK;
     Register temp = ToRegister(instr->TempAt(0));
     int offset = Context::SlotOffset(instr->slot_index());
     __ RecordWriteContextSlot(context,
                               offset,
                               value,
                               temp,
                               kSaveFPRegs,
                               EMIT_REMEMBERED_SET,
                               check_needed);
   }
+
+  __ bind(&skip_assignment);
 }
 
 
 void LCodeGen::DoLoadNamedField(LLoadNamedField* instr) {
   Register object = ToRegister(instr->object());
   Register result = ToRegister(instr->result());
   if (instr->hydrogen()->is_in_object()) {
     __ mov(result, FieldOperand(object, instr->hydrogen()->offset()));
   } else {
     __ mov(result, FieldOperand(object, JSObject::kPropertiesOffset));
@@ skipping 2409 matching lines @@
       this, pointers, Safepoint::kLazyDeopt);
   __ InvokeBuiltin(Builtins::IN, CALL_FUNCTION, safepoint_generator);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32