Be careful with predecessor/successor index.

When we simplify the CFG, we must preserve things that were already
simplified. For example, the index in the predecessor list or
successor list of a block must be preserved for ensuring the
first block is a loop pre header.

bug:21867463

(cherry picked from commit 8b20f88b0a8d1b374dd5eaae289d19734c77b8f8)

Change-Id: I2581b5a50942290da96cd9ec876f6f2573e0a6c4

5 files changed, 73 insertions, 2 deletions

diff --git a/test/485-checker-dce-loop-update/smali/TestCase.smali b/test/485-checker-dce-loop-update/smali/TestCase.smali
index 3873ac5..6a42a46 100644
--- a/test/485-checker-dce-loop-update/smali/TestCase.smali
+++ b/test/485-checker-dce-loop-update/smali/TestCase.smali
@@ -141,7 +141,7 @@
 # CHECK-DAG:                    If [ [[ArgY]] ]                              loop_header:[[HeaderY]]
 # CHECK-DAG:                    If [ [[ArgZ]] ]                              loop_header:[[HeaderY]]
 # CHECK-DAG:     [[Mul9:i\d+]]  Mul [ [[PhiX1]] [[Cst9]] ]                   loop_header:[[HeaderY]]
-# CHECK-DAG:     [[PhiX2:i\d+]] Phi [ [[Mul9]] [[PhiX1]] ]                   loop_header:[[HeaderY]]
+# CHECK-DAG:     [[PhiX2:i\d+]] Phi [ [[PhiX1]] [[Mul9]] ]                   loop_header:[[HeaderY]]
 # CHECK-DAG:                    If [ [[Cst1]] ]                              loop_header:[[HeaderY]]
 # CHECK-DAG:     [[Add5]]       Add [ [[PhiX2]] [[Cst5]] ]                   loop_header:[[HeaderY]]
 # CHECK-DAG:     [[Add7]]       Add [ [[PhiX1]] [[Cst7]] ]                   loop_header:[[HeaderY]]
@@ -158,7 +158,7 @@
 # CHECK-DAG:     [[Add7]]       Add [ [[PhiX1]] [[Cst7]] ]                   loop_header:[[HeaderY]]
 # CHECK-DAG:                    If [ [[ArgZ]] ]                              loop_header:null
 # CHECK-DAG:     [[Mul9:i\d+]]  Mul [ [[PhiX1]] [[Cst9]] ]                   loop_header:null
-# CHECK-DAG:     [[PhiX2:i\d+]] Phi [ [[Mul9]] [[PhiX1]] ]                   loop_header:null
+# CHECK-DAG:     [[PhiX2:i\d+]] Phi [ [[PhiX1]] [[Mul9]] ]                   loop_header:null
 # CHECK-DAG:                    Return [ [[PhiX2]] ]                         loop_header:null
 
 .method public static testExitPredecessors(IZZ)I
diff --git a/test/509-pre-header/expected.txt b/test/509-pre-header/expected.txt
new file mode 100644
index 0000000..ccaf6f8
--- /dev/null
+++ b/test/509-pre-header/expected.txt
@@ -0,0 +1 @@
+Enter
diff --git a/test/509-pre-header/info.txt b/test/509-pre-header/info.txt
new file mode 100644
index 0000000..e9d8b94
--- /dev/null
+++ b/test/509-pre-header/info.txt
@@ -0,0 +1,3 @@
+Regression test for the SimplifyCFG phase of optimizing.
+The invariant that the pre header of a loop header is the
+first predecessor was not preserved.
diff --git a/test/509-pre-header/smali/PreHeader.smali b/test/509-pre-header/smali/PreHeader.smali
new file mode 100644
index 0000000..04f4e49
--- /dev/null
+++ b/test/509-pre-header/smali/PreHeader.smali
@@ -0,0 +1,39 @@
+# 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.
+
+.class public LPreHeader;
+
+.super Ljava/lang/Object;
+
+# Label names in this method are taken from the original apk
+# that exposed the crash. The crash was due to fixing a critical
+# edge and not preserving the invariant that the pre header of a loop
+# is the first predecessor of the loop header.
+.method public static method()V
+   .registers 2
+   const/4 v0, 0
+   const/4 v1, 0
+   goto :b31
+   :b23
+   if-eqz v0, :b25
+   goto :b23
+   :b25
+   return-void
+   :b31
+   if-eqz v0, :b23
+   if-eqz v1, :bexit
+   goto :b31
+   :bexit
+   return-void
+.end method
diff --git a/test/509-pre-header/src/Main.java b/test/509-pre-header/src/Main.java
new file mode 100644
index 0000000..1eca419
--- /dev/null
+++ b/test/509-pre-header/src/Main.java
@@ -0,0 +1,28 @@
+/*
+ * 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 java.lang.reflect.Method;
+
+public class Main {
+  public static void main(String[] args) throws Exception {
+    // Workaround for b/18051191.
+    System.out.println("Enter");
+    Class<?> c = Class.forName("PreHeader");
+    Method m = c.getMethod("method");
+    Object[] arguments = { };
+    m.invoke(null, arguments);
+  }
+}