src/cpu/aarch64/vm/jniFastGetField_aarch64.cpp

rev 12692 : 8176100: [REDO][REDO] G1 Needs pre barrier on dereference of weak JNI handles
Reviewed-by:

@@ -1,7 +1,7 @@
 /*
- * Copyright (c) 2004, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2004, 2017, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2014, Red Hat Inc. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as

@@ -80,10 +80,15 @@
   __ cbnzw(rscratch1, slow);
   __ eor(robj, c_rarg1, rcounter);
   __ eor(robj, robj, rcounter);               // obj, since
                                               // robj ^ rcounter ^ rcounter == robj
                                               // robj is address dependent on rcounter.
+
+  // If mask changes we need to ensure that the inverse is still encodable as an immediate
+  STATIC_ASSERT(JNIHandles::weak_tag_mask == 1);
+  __ andr(robj, robj, ~JNIHandles::weak_tag_mask);
+
   __ ldr(robj, Address(robj, 0));             // *obj
   __ lsr(roffset, c_rarg2, 2);                // offset
 
   assert(count < LIST_CAPACITY, "LIST_CAPACITY too small");
   speculative_load_pclist[count] = __ pc();   // Used by the segfault handler