am 6e9c66e0: Fix a bug in the register allocator around pair allocation.

* commit '6e9c66e099654b63ed3648bda2daeaf0a862f047':
  Fix a bug in the register allocator around pair allocation.

4 files changed, 51 insertions, 1 deletions

diff --git a/compiler/optimizing/register_allocator.cc b/compiler/optimizing/register_allocator.cc
index 8656ad5f8c..d64e146ff0 100644
--- a/compiler/optimizing/register_allocator.cc
+++ b/compiler/optimizing/register_allocator.cc
@@ -772,7 +772,10 @@ bool RegisterAllocator::TryAllocateFreeReg(LiveInterval* current) {
   } else {
     DCHECK(!current->IsHighInterval());
     int hint = current->FindFirstRegisterHint(free_until, liveness_);
-    if (hint != kNoRegister) {
+    if ((hint != kNoRegister)
+        // For simplicity, if the hint we are getting for a pair cannot be used,
+        // we are just going to allocate a new pair.
+        && !(current->IsLowInterval() && IsBlocked(GetHighForLowRegister(hint)))) {
       DCHECK(!IsBlocked(hint));
       reg = hint;
     } else if (current->IsLowInterval()) {
diff --git a/test/528-long-hint/expected.txt b/test/528-long-hint/expected.txt
new file mode 100644
index 0000000000..e69de29bb2
--- /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 0000000000..6a9cfaec36
--- /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 0000000000..ca1a114a7a
--- /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);
+  }
+}