From ec32b91cfa1061b2608838d41e6d7d70fdf681dc Mon Sep 17 00:00:00 2001
From: Roland Levillain <rpl@google.com>
Date: Fri, 21 Oct 2016 14:47:26 +0100
Subject: [PATCH] Remove read barrier in UnstartedUnsafeCompareAndSwapLong.

art::interpreter::UnstartedRuntime::UnstartedUnsafeCompareAndSwapLong
manipulates a long field and does not need a read barrier
(read barriers are only required when loading an object
reference from the heap).

Test: ART_USE_READ_BARRIER=true make test-art-host
Bug: 12687968
Change-Id: Ia46590e649a7bb46ca4b3c90bab03fb3a836563d
---
 runtime/interpreter/unstarted_runtime.cc | 13 -------------
 1 file changed, 13 deletions(-)

diff --git a/runtime/interpreter/unstarted_runtime.cc b/runtime/interpreter/unstarted_runtime.cc
index 25ce5cc4e..5a62bd77d 100644
--- a/runtime/interpreter/unstarted_runtime.cc
+++ b/runtime/interpreter/unstarted_runtime.cc
@@ -1238,19 +1238,6 @@ void UnstartedRuntime::UnstartedUnsafeCompareAndSwapLong(
   int64_t offset = shadow_frame->GetVRegLong(arg_offset + 2);
   int64_t expectedValue = shadow_frame->GetVRegLong(arg_offset + 4);
   int64_t newValue = shadow_frame->GetVRegLong(arg_offset + 6);
-
-  // Must use non transactional mode.
-  if (kUseReadBarrier) {
-    // Need to make sure the reference stored in the field is a to-space one before attempting the
-    // CAS or the CAS could fail incorrectly.
-    mirror::HeapReference<mirror::Object>* field_addr =
-        reinterpret_cast<mirror::HeapReference<mirror::Object>*>(
-            reinterpret_cast<uint8_t*>(obj) + static_cast<size_t>(offset));
-    ReadBarrier::Barrier<mirror::Object, kWithReadBarrier, /*kAlwaysUpdateField*/true>(
-        obj,
-        MemberOffset(offset),
-        field_addr);
-  }
   bool success;
   // Check whether we're in a transaction, call accordingly.
   if (Runtime::Current()->IsActiveTransaction()) {
-- 
2.11.0