Remove bogus DCHECK in BCE.

When creating a phi for the array length when we add HDeoptimization
nodes, we might update accesses in inner loops to use that phi instead
of the array length. The BCE phase was not expecting this case.

Change-Id: I639f4ea6f5889726142041a42736183f162c7437

4 files changed, 49 insertions, 5 deletions

diff --git a/compiler/optimizing/bounds_check_elimination.cc b/compiler/optimizing/bounds_check_elimination.cc
index 9d5e3fdca1..97b3725da1 100644
--- a/compiler/optimizing/bounds_check_elimination.cc
+++ b/compiler/optimizing/bounds_check_elimination.cc
@@ -335,12 +335,12 @@ class ArrayAccessInsideLoopFinder : public ValueObject {
           continue;
         }
 
-        DCHECK(!length_value->IsPhi());
         if (length_value->IsPhi()) {
-          // Outer loop shouldn't collect bounds checks inside inner
-          // loop because the inner loop body doen't dominate
-          // outer loop's back edges. However just to be on the safe side,
-          // if there are any such cases, we just skip over them.
+          // When adding deoptimizations in outer loops, we might create
+          // a phi for the array length, and update all uses of the
+          // length in the loop to that phi. Therefore, inner loops having
+          // bounds checks on the same array will use that phi.
+          // TODO: handle these cases.
           continue;
         }
 
diff --git a/test/499-bce-phi-array-length/expected.txt b/test/499-bce-phi-array-length/expected.txt
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/test/499-bce-phi-array-length/expected.txt
diff --git a/test/499-bce-phi-array-length/info.txt b/test/499-bce-phi-array-length/info.txt
new file mode 100644
index 0000000000..ee52699579
--- /dev/null
+++ b/test/499-bce-phi-array-length/info.txt
@@ -0,0 +1,2 @@
+Regression test for BCE phase of optimizing. See Main.java
+for a description of the bug.
diff --git a/test/499-bce-phi-array-length/src/Main.java b/test/499-bce-phi-array-length/src/Main.java
new file mode 100644
index 0000000000..c8c84a1a8f
--- /dev/null
+++ b/test/499-bce-phi-array-length/src/Main.java
@@ -0,0 +1,42 @@
+/*
+ * 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.
+ */
+
+public class Main {
+  public static int foo(int start, int[] array) {
+    int result = 0;
+    // We will create HDeoptimize nodes for this first loop, and a phi
+    // for the array length which will only be used within the loop.
+    for (int i = start; i < 3; i++) {
+      result += array[i];
+      for (int j = 0; j < 2; ++j) {
+        // The HBoundsCheck for this array access will be updated to access
+        // the array length phi created for the deoptimization checks of the
+        // first loop. This crashed the compiler which used to DCHECK an array
+        // length in a bounds check cannot be a phi.
+        result += array[j];
+      }
+    }
+    return result;
+  }
+
+  public static void main(String[] args) {
+    int[] a = new int[] { 1, 2, 3, 4, 5 };
+    int result = foo(1, a);
+    if (result != 11) {
+      throw new Error("Got " + result + ", expected " + 11);
+    }
+  }
+}