10 files changed, 118 insertions, 3 deletions
diff --git a/compiler/optimizing/bounds_check_elimination.cc b/compiler/optimizing/bounds_check_elimination.cc
index 97b3725da1..900dabea0e 100644
--- a/compiler/optimizing/bounds_check_elimination.cc
+++ b/compiler/optimizing/bounds_check_elimination.cc
@@ -1759,7 +1759,9 @@ class BCEVisitor : public HGraphVisitor {
     ValueBound lower_bound = range->GetLower();
     DCHECK(lower_bound.IsConstant());
     DCHECK(const_instr->GetValue() <= kMaxConstantForAddingDeoptimize);
-    DCHECK_EQ(lower_bound.GetConstant(), const_instr->GetValue() + 1);
+    // Note that the lower bound of the array length may have been refined
+    // through other instructions (such as `HNewArray(length - 4)`).
+    DCHECK_LE(const_instr->GetValue() + 1, lower_bound.GetConstant());
 
     // If array_length is less than lower_const, deoptimize.
     HBoundsCheck* bounds_check = first_constant_index_bounds_check_map_.Get(
diff --git a/compiler/optimizing/nodes.cc b/compiler/optimizing/nodes.cc
index c294294580..fb150c3fa8 100644
--- a/compiler/optimizing/nodes.cc
+++ b/compiler/optimizing/nodes.cc
@@ -287,7 +287,10 @@ void HGraph::InsertConstant(HConstant* constant) {
 }
 
 HNullConstant* HGraph::GetNullConstant() {
-  if (cached_null_constant_ == nullptr) {
+  // For simplicity, don't bother reviving the cached null constant if it is
+  // not null and not in a block. Otherwise, we need to clear the instruction
+  // id and/or any invariants the graph is assuming when adding new instructions.
+  if ((cached_null_constant_ == nullptr) || (cached_null_constant_->GetBlock() == nullptr)) {
     cached_null_constant_ = new (arena_) HNullConstant();
     InsertConstant(cached_null_constant_);
   }
diff --git a/compiler/optimizing/optimizing_compiler.cc b/compiler/optimizing/optimizing_compiler.cc
index 5632434c0f..64d6023fba 100644
--- a/compiler/optimizing/optimizing_compiler.cc
+++ b/compiler/optimizing/optimizing_compiler.cc
@@ -342,9 +342,9 @@ static void RunOptimizations(HGraph* graph,
 
   HOptimization* optimizations[] = {
     &intrinsics,
-    &dce1,
     &fold1,
     &simplify1,
+    &dce1,
     &inliner,
     // BooleanSimplifier depends on the InstructionSimplifier removing redundant
     // suspend checks to recognize empty blocks.
diff --git a/test/501-null-constant-dce/expected.txt b/test/501-null-constant-dce/expected.txt
new file mode 100644
index 0000000000..ccaf6f8f0f
--- /dev/null
+++ b/test/501-null-constant-dce/expected.txt
@@ -0,0 +1 @@
+Enter
diff --git a/test/501-null-constant-dce/info.txt b/test/501-null-constant-dce/info.txt
new file mode 100644
index 0000000000..2c4a686b5f
--- /dev/null
+++ b/test/501-null-constant-dce/info.txt
@@ -0,0 +1 @@
+Regression test for the optimizing compiler. See comment in smali file.
diff --git a/test/501-null-constant-dce/smali/DCE.smali b/test/501-null-constant-dce/smali/DCE.smali
new file mode 100644
index 0000000000..4a1765e796
--- /dev/null
+++ b/test/501-null-constant-dce/smali/DCE.smali
@@ -0,0 +1,37 @@
+# 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 LDCE;
+
+.super Ljava/lang/Object;
+
+.method public static method([I)LDCE;
+   .registers 2
+   const/4 v0, 0
+   # Jump over the code that requires the null constant
+   # so that the compiler sees the null constant as dead code.
+   if-eq v0, v0, :end
+   invoke-static {v0}, LDCE;->method([I)LDCE;
+   :end
+   invoke-static {}, LDCE;->$inline$returnNull()LDCE;
+   move-result-object v0
+   return-object v0
+.end method
+
+.method public static $inline$returnNull()LDCE;
+   .registers 2
+   const/4 v0, 0
+   # Return null to make `method` call GetConstantNull again.
+   return-object v0
+.end method
diff --git a/test/501-null-constant-dce/src/Main.java b/test/501-null-constant-dce/src/Main.java
new file mode 100644
index 0000000000..3a2d491b15
--- /dev/null
+++ b/test/501-null-constant-dce/src/Main.java
@@ -0,0 +1,32 @@
+/*
+ * 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("DCE");
+    Method m = c.getMethod("method", int[].class);
+    int[] array = new int[7];
+    Object[] arguments = { array };
+    Object result = m.invoke(null, arguments);
+    if (result != null) {
+      throw new Error("Expected null, got " + result);
+    }
+  }
+}
diff --git a/test/513-array-deopt/expected.txt b/test/513-array-deopt/expected.txt
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/test/513-array-deopt/expected.txt
diff --git a/test/513-array-deopt/info.txt b/test/513-array-deopt/info.txt
new file mode 100644
index 0000000000..afce9d9942
--- /dev/null
+++ b/test/513-array-deopt/info.txt
@@ -0,0 +1,2 @@
+Regression test for the BCE phase of optimizing,
+that used to have wrong assumptions about array length bounds.
diff --git a/test/513-array-deopt/src/Main.java b/test/513-array-deopt/src/Main.java
new file mode 100644
index 0000000000..a0ae4c3556
--- /dev/null
+++ b/test/513-array-deopt/src/Main.java
@@ -0,0 +1,37 @@
+/*
+ * 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[] bar(int[] a) {
+    a[0] = 0;
+    a[1] = 0;
+    a[2] = 0;
+    // Up to this point, we record that the lower bound is 2.
+    // The next instruction will record that the lower bound is 5.
+    // The deoptimization code used to assume the lower bound has
+    // to be check it will add for the deoptimization (here, it
+    // would be 2).
+    return new int[a.length - 5];
+  }
+
+  public static void main(String[] args) {
+    int[] a = new int[5];
+    a = bar(a);
+    if (a.length != 0) {
+      throw new Error("Expected 0, got " + a.length);
+    }
+  }
+}