Fix a bug in the register allocator around pair allocation.

We may get hints that do not work with the current implementation
of register pairs, which forces the allocation of (low + 1)
for the high register. For example, if the hint is EBX, we will
allocate ESP for the high register.

bug:23043730

(cherry picked from commit f29758111e71a7d14f3e52d78773561a5d59961f)

Change-Id: Ib395e36616017a87d3055218d72417f4e9ff6501

3 files changed, 47 insertions, 0 deletions

diff --git a/test/528-long-hint/expected.txt b/test/528-long-hint/expected.txt
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/test/528-long-hint/expected.txt
diff --git a/test/528-long-hint/info.txt b/test/528-long-hint/info.txt
new file mode 100644
index 0000000..6a9cfae
--- /dev/null
+++ b/test/528-long-hint/info.txt
@@ -0,0 +1,2 @@
+Regression test for optimizing that used to crash on x86 when
+allocating a wrong register pair.
diff --git a/test/528-long-hint/src/Main.java b/test/528-long-hint/src/Main.java
new file mode 100644
index 0000000..ca1a114
--- /dev/null
+++ b/test/528-long-hint/src/Main.java
@@ -0,0 +1,45 @@
+/*
+ * Copyright (C) 2015 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 sun.misc.Unsafe;
+import java.lang.reflect.Field;
+
+public class Main {
+
+  long instanceField;
+  static long myLongField1;
+  static long myLongField2;
+
+  public static void main(String[] args) throws Exception {
+    Unsafe unsafe = getUnsafe();
+    Main f = new Main();
+    long offset = unsafe.objectFieldOffset(Main.class.getDeclaredField("instanceField"));
+    getUnsafe(); // spill offset
+    long a = myLongField1;
+    // We used the hinted register for the low part of b, which is EBX, as requested
+    // by the intrinsic below. Allocating EBX for the low part, would put ESP as the high
+    // part, and we did not check that ESP was blocked.
+    long b = myLongField2;
+    unsafe.compareAndSwapLong(f, offset, a, b);
+  }
+
+
+  private static Unsafe getUnsafe() throws Exception {
+    Field f = Unsafe.class.getDeclaredField("theUnsafe");
+    f.setAccessible(true);
+    return (Unsafe) f.get(null);
+  }
+}