ART: Fix simplification of catch blocks in the presence of dead code

Simplification of catch blocks transforms the code so that catch
blocks have only exceptional predecessors. However, it is invoked
before trivially dead code is eliminated which breaks simple
assumptions such as the fact that a catch block cannot start with
move-exception if it has non-exceptional predecessors. This patch
fixes the algorithm to work under these relaxed conditions.

Bug: 25494450
Bug: 25492628
Change-Id: Idc8d010102a4b8b9a6cd918b98d6e11d1838db0c

4 files changed, 130 insertions, 0 deletions

diff --git a/test/546-regression-simplify-catch/expected.txt b/test/546-regression-simplify-catch/expected.txt
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/test/546-regression-simplify-catch/expected.txt
diff --git a/test/546-regression-simplify-catch/info.txt b/test/546-regression-simplify-catch/info.txt
new file mode 100644
index 0000000000..b146e87bc9
--- /dev/null
+++ b/test/546-regression-simplify-catch/info.txt
@@ -0,0 +1,2 @@
+Tests simplification of catch blocks in the presence of trivially dead code
+that was not verified by the verifier.
diff --git a/test/546-regression-simplify-catch/smali/TestCase.smali b/test/546-regression-simplify-catch/smali/TestCase.smali
new file mode 100644
index 0000000000..486b3b0c4b
--- /dev/null
+++ b/test/546-regression-simplify-catch/smali/TestCase.smali
@@ -0,0 +1,104 @@
+# 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 LTestCase;
+.super Ljava/lang/Object;
+
+# Test simplification of an empty, dead catch block. Compiler used to segfault
+# because it did expect at least a control-flow instruction (b/25494450).
+
+.method public static testCase_EmptyCatch()I
+    .registers 3
+
+    const v0, 0x0
+    return v0
+
+    :try_start
+    nop
+    :try_end
+    .catchall {:try_start .. :try_end} :catch
+
+    nop
+
+    :catch
+    nop
+
+.end method
+
+# Test simplification of a dead catch block with some code but no control-flow
+# instruction.
+
+.method public static testCase_NoConrolFlowCatch()I
+    .registers 3
+
+    const v0, 0x0
+    return v0
+
+    :try_start
+    nop
+    :try_end
+    .catchall {:try_start .. :try_end} :catch
+
+    nop
+
+    :catch
+    const v1, 0x3
+    add-int v0, v0, v1
+
+.end method
+
+# Test simplification of a dead catch block with normal-predecessors but
+# starting with a move-exception. Verifier does not check trivially dead code
+# and this used to trip a DCHECK (b/25492628).
+
+.method public static testCase_InvalidLoadException()I
+    .registers 3
+
+    const v0, 0x0
+    return v0
+
+    :try_start
+    nop
+    :try_end
+    .catchall {:try_start .. :try_end} :catch
+
+    :catch
+    move-exception v0
+
+.end method
+
+# Test simplification of a live catch block with dead normal-predecessors and
+# starting with a move-exception. Verifier does not check trivially dead code
+# and this used to trip a DCHECK (b/25492628).
+
+.method public static testCase_TriviallyDeadPredecessor(II)I
+    .registers 3
+
+    :try_start
+    div-int v0, p0, p1
+    return v0
+    :try_end
+    .catchall {:try_start .. :try_end} :catch
+
+    # Trivially dead predecessor block.
+    add-int p0, p0, p1
+
+    :catch
+    # This verifies because only exceptional predecessors are live.
+    move-exception v0
+    const v0, 0x0
+    return v0
+
+.end method
+
diff --git a/test/546-regression-simplify-catch/src/Main.java b/test/546-regression-simplify-catch/src/Main.java
new file mode 100644
index 0000000000..8eddac3fea
--- /dev/null
+++ b/test/546-regression-simplify-catch/src/Main.java
@@ -0,0 +1,24 @@
+/*
+ * 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 {
+
+  // Workaround for b/18051191.
+  class InnerClass {}
+
+  public static void main(String[] args) {}
+
+}