Add reachabilityFence intrinsics
Add intrinsics that generate no code or do nothing for all architectures
and for the interpreter. The only impact is to keep the argument live at
all suspend points preceding the call. We ensure that the code is not
moved across other memory accesses by declaring it to have write side-effects.
Add a minimal test.
Modify 036-finalizer to use a reachabilityFence, hopefully making it
more robust to dead refererence elimination.
Bug: 72698200
Test: Build and boot AOSP.
art/test.py --host -r -t 072-reachability-fence
Look at generated code.
Change-Id: I0f298bf5cc375d8ebc19bb791cc05a8490d55430
diff --git a/test/072-reachability-fence/src/Main.java b/test/072-reachability-fence/src/Main.java
new file mode 100644
index 0000000..ac1e131
--- /dev/null
+++ b/test/072-reachability-fence/src/Main.java
@@ -0,0 +1,61 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import java.lang.ref.Reference;
+import java.lang.ref.WeakReference;
+
+public class Main {
+ public static void main(String[] args) {
+ System.out.println("Starting");
+ WeakReference wrefs[] = new WeakReference[5];
+ String str0 = generateString("String", 0);
+ String str1 = generateString("String", 1);
+ String str2 = generateString("String", 2);
+ String str3 = generateString("String", 3);
+ String str4 = generateString("String", 4);
+ wrefs[0] = new WeakReference(str0);
+ wrefs[1] = new WeakReference(str1);
+ wrefs[2] = new WeakReference(str2);
+ wrefs[3] = new WeakReference(str3);
+ wrefs[4] = new WeakReference(str4);
+ // Clear a couple as a sanity check.
+ str1 = null;
+ str2 = null;
+ // str<n> dead here; in the future we will possibly reuse the registers.
+ // Give the compiler something to fill the registers with.
+ String str5 = generateString("String", 5);
+ String str6 = generateString("String", 6);
+ String str7 = generateString("String", 7);
+ String str8 = generateString("String", 8);
+ String str9 = generateString("String", 9);
+ Runtime.getRuntime().gc();
+ for (int i = 0; i < 5; ++i) {
+ if (wrefs[i].get() != null) {
+ System.out.println("Reference " + i + " was live.");
+ }
+ }
+ Reference.reachabilityFence(str0);
+ Reference.reachabilityFence(str1);
+ Reference.reachabilityFence(str2);
+ Reference.reachabilityFence(str3);
+ Reference.reachabilityFence(str4);
+ System.out.println("Finished");
+ }
+
+ private static String generateString(String base, int num) {
+ return base + num;
+ }
+}