Update prebuilt Clang to match Android kernel.

Bug: 132428451
Change-Id: I8f6e2cb23f381fc0c02ddea99b867e58e925e5be
diff --git a/linux-x64/clang/include/llvm/CodeGen/MachineMemOperand.h b/linux-x64/clang/include/llvm/CodeGen/MachineMemOperand.h
index 078ef7c..12fae2f 100644
--- a/linux-x64/clang/include/llvm/CodeGen/MachineMemOperand.h
+++ b/linux-x64/clang/include/llvm/CodeGen/MachineMemOperand.h
@@ -1,9 +1,8 @@
 //==- llvm/CodeGen/MachineMemOperand.h - MachineMemOperand class -*- C++ -*-==//
 //
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
@@ -267,13 +266,13 @@
   bool isAtomic() const { return getOrdering() != AtomicOrdering::NotAtomic; }
 
   /// Returns true if this memory operation doesn't have any ordering
-  /// constraints other than normal aliasing. Volatile and atomic memory
-  /// operations can't be reordered.
-  ///
-  /// Currently, we don't model the difference between volatile and atomic
-  /// operations. They should retain their ordering relative to all memory
-  /// operations.
-  bool isUnordered() const { return !isVolatile(); }
+  /// constraints other than normal aliasing. Volatile and (ordered) atomic
+  /// memory operations can't be reordered. 
+  bool isUnordered() const {
+    return (getOrdering() == AtomicOrdering::NotAtomic ||
+            getOrdering() == AtomicOrdering::Unordered) &&
+           !isVolatile();
+  }
 
   /// Update this MachineMemOperand to reflect the alignment of MMO, if it has a
   /// greater alignment. This must only be used when the new alignment applies