From 54dce35f6025093995f5cb7d14e5c32941ba6004 Mon Sep 17 00:00:00 2001
From: Xin Liu <xxinliu@amazon.com>
Date: Sat, 13 Jul 2019 16:16:56 -0700
Subject: [PATCH] amend arm64 specific code for weak JNI handles

---
 .../aarch64/vm/jniFastGetField_aarch64.cpp    |  6 ++++
 .../cpu/aarch64/vm/sharedRuntime_aarch64.cpp  | 31 +++++++++++++++----
 .../vm/templateInterpreter_aarch64.cpp        | 26 ++++++++++++++--
 3 files changed, 54 insertions(+), 9 deletions(-)

diff --git a/src/hotspot/src/cpu/aarch64/vm/jniFastGetField_aarch64.cpp b/src/hotspot/src/cpu/aarch64/vm/jniFastGetField_aarch64.cpp
index d3c56f65538..ab0204addf3 100644
--- a/src/hotspot/src/cpu/aarch64/vm/jniFastGetField_aarch64.cpp
+++ b/src/hotspot/src/cpu/aarch64/vm/jniFastGetField_aarch64.cpp
@@ -1,4 +1,5 @@
 /*
+ * Copyright (c) 2003, 2018, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2014, Red Hat Inc.
  * Copyright (c) 2004, 2010, Oracle and/or its affiliates.
  * All rights reserved.
@@ -82,6 +83,11 @@ address JNI_FastGetField::generate_fast_get_int_field0(BasicType type) {
   __ 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
 
diff --git a/src/hotspot/src/cpu/aarch64/vm/sharedRuntime_aarch64.cpp b/src/hotspot/src/cpu/aarch64/vm/sharedRuntime_aarch64.cpp
index 7a5ae55cc38..b8f7a830456 100644
--- a/src/hotspot/src/cpu/aarch64/vm/sharedRuntime_aarch64.cpp
+++ b/src/hotspot/src/cpu/aarch64/vm/sharedRuntime_aarch64.cpp
@@ -1,4 +1,5 @@
 /*
+ * Copyright (c) 2003, 2018, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2013, Red Hat Inc.
  * Copyright (c) 2003, 2012, Oracle and/or its affiliates.
  * All rights reserved.
@@ -2050,13 +2051,31 @@ nmethod* SharedRuntime::generate_native_wrapper(MacroAssembler* masm,
 
   __ reset_last_Java_frame(false);
 
-  // Unpack oop result
+  // Unbox oop result, e.g. JNIHandles::resolve result.
   if (ret_type == T_OBJECT || ret_type == T_ARRAY) {
-      Label L;
-      __ cbz(r0, L);
-      __ ldr(r0, Address(r0, 0));
-      __ bind(L);
-      __ verify_oop(r0);
+    Label done, not_weak;
+    __ cbz(r0, done);           // Use NULL as-is.
+    STATIC_ASSERT(JNIHandles::weak_tag_mask == 1u);
+    __ tbz(r0, 0, not_weak);    // Test for jweak tag.
+    // Resolve jweak.
+    __ ldr(r0, Address(r0, -JNIHandles::weak_tag_value));
+    __ verify_oop(r0);
+#if INCLUDE_ALL_GCS
+    if (UseG1GC) {
+      __ g1_write_barrier_pre(noreg /* obj */,
+                              r0 /* pre_val */,
+                              rthread /* thread */,
+                              rscratch1 /* tmp */,
+                              true /* tosca_live */,
+                              true /* expand_call */);
+    }
+#endif // INCLUDE_ALL_GCS
+    __ b(done);
+    __ bind(not_weak);
+    // Resolve (untagged) jobject.
+    __ ldr(r0, Address(r0, 0));
+    __ verify_oop(r0);
+    __ bind(done);
   }
 
   if (!is_critical_native) {
diff --git a/src/hotspot/src/cpu/aarch64/vm/templateInterpreter_aarch64.cpp b/src/hotspot/src/cpu/aarch64/vm/templateInterpreter_aarch64.cpp
index 5361527bcca..75f5d775d83 100644
--- a/src/hotspot/src/cpu/aarch64/vm/templateInterpreter_aarch64.cpp
+++ b/src/hotspot/src/cpu/aarch64/vm/templateInterpreter_aarch64.cpp
@@ -1,4 +1,5 @@
 /*
+ * Copyright (c) 2003, 2018, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2013, Red Hat Inc.
  * Copyright (c) 2003, 2011, Oracle and/or its affiliates.
  * All rights reserved.
@@ -1194,13 +1195,32 @@ address InterpreterGenerator::generate_native_entry(bool synchronized) {
   // and result handler will pick it up
 
   {
-    Label no_oop, store_result;
+    Label no_oop, not_weak, store_result;
     __ adr(t, ExternalAddress(AbstractInterpreter::result_handler(T_OBJECT)));
     __ cmp(t, result_handler);
     __ br(Assembler::NE, no_oop);
-    // retrieve result
+    // Unbox oop result, e.g. JNIHandles::resolve result.
     __ pop(ltos);
-    __ cbz(r0, store_result);
+    __ cbz(r0, store_result); // Use NULL as-is.
+    STATIC_ASSERT(JNIHandles::weak_tag_mask == 1u);
+    __ tbz(r0, 0, not_weak);    // Test for jweak tag.
+    // Resolve jweak.
+    __ ldr(r0, Address(r0, -JNIHandles::weak_tag_value));
+#if INCLUDE_ALL_GCS
+    if (UseG1GC) {
+      __ enter();                   // Barrier may call runtime.
+      __ g1_write_barrier_pre(noreg /* obj */,
+                              r0 /* pre_val */,
+                              rthread /* thread */,
+                              t /* tmp */,
+                              true /* tosca_live */,
+                              true /* expand_call */);
+      __ leave();
+    }
+#endif // INCLUDE_ALL_GCS
+    __ b(store_result);
+    __ bind(not_weak);
+    // Resolve (untagged) jobject.
     __ ldr(r0, Address(r0, 0));
     __ bind(store_result);
     __ str(r0, Address(rfp, frame::interpreter_frame_oop_temp_offset*wordSize));