ART: Implicit null check should break def tracking

Implicit null check can provoke exception that needs to be sure all VRs are saved on stack.
The fix is to reset the def tracking system at the moment of adding an implicit null check.

  b/18368901

Signed-off-by: Pavel Vyssotski <pavel.n.vyssotski@intel.com>

(cherry picked from commit 9c3617a8f7413bb1181e72bc1f7086d986a86e18)

Change-Id: If7d705b8417cf29076da9ce19ec54d698f3cb0d5
diff --git a/compiler/dex/quick/gen_common.cc b/compiler/dex/quick/gen_common.cc
index f6c77fc..7381f19 100644
--- a/compiler/dex/quick/gen_common.cc
+++ b/compiler/dex/quick/gen_common.cc
@@ -160,6 +160,10 @@
   if (!cu_->compiler_driver->GetCompilerOptions().GetImplicitNullChecks()) {
     return GenExplicitNullCheck(m_reg, opt_flags);
   }
+  // If null check has not been eliminated, reset redundant store tracking.
+  if ((opt_flags & MIR_IGNORE_NULL_CHECK) == 0) {
+    ResetDefTracking();
+  }
   return nullptr;
 }
 
diff --git a/test/128-reg-spilling-on-implicit-nullcheck/expected.txt b/test/128-reg-spilling-on-implicit-nullcheck/expected.txt
new file mode 100644
index 0000000..9bdf6588
--- /dev/null
+++ b/test/128-reg-spilling-on-implicit-nullcheck/expected.txt
@@ -0,0 +1 @@
+t7q = 2
diff --git a/test/128-reg-spilling-on-implicit-nullcheck/info.txt b/test/128-reg-spilling-on-implicit-nullcheck/info.txt
new file mode 100644
index 0000000..18b2112
--- /dev/null
+++ b/test/128-reg-spilling-on-implicit-nullcheck/info.txt
@@ -0,0 +1 @@
+This is a compiler reggression test for missing reg spilling on implicit nullcheck.
diff --git a/test/128-reg-spilling-on-implicit-nullcheck/src/Main.java b/test/128-reg-spilling-on-implicit-nullcheck/src/Main.java
new file mode 100644
index 0000000..48276bf
--- /dev/null
+++ b/test/128-reg-spilling-on-implicit-nullcheck/src/Main.java
@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2007 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 void main(String[] args) {
+        int t7q = 0;
+        long q = 1L;
+
+        try {
+            for (int i = 1; i < 8; i++) {
+                t7q = (--t7q);
+                TestClass f = null;
+                t7q = f.field;
+            }
+        }
+        catch (NullPointerException wpw) {
+            q++;
+        }
+        finally {
+            t7q += (int)(1 - ((q - q) - 2));
+        }
+
+        System.out.println("t7q = " + t7q);
+    }
+}
+
+class TestClass {
+    public int field;
+    public void meth() {field = 1;}
+}