Add runtime reasons for deopt.

Currently to help investigate. Also:
1) Log when deoptimization happens (which method and what reason)
2) Trace when deoptimization happens (to make it visible in systrace)

bug:37655083
Test: test-art-host test-art-target
Change-Id: I0c2d87b40db09e8e475cf97a7c784a034c585e97
diff --git a/runtime/deoptimization_kind.h b/runtime/deoptimization_kind.h
new file mode 100644
index 0000000..14e189c
--- /dev/null
+++ b/runtime/deoptimization_kind.h
@@ -0,0 +1,53 @@
+/*
+ * Copyright (C) 2017 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.
+ */
+
+#ifndef ART_RUNTIME_DEOPTIMIZATION_KIND_H_
+#define ART_RUNTIME_DEOPTIMIZATION_KIND_H_
+
+namespace art {
+
+enum class DeoptimizationKind {
+  kAotInlineCache = 0,
+  kJitInlineCache,
+  kJitSameTarget,
+  kLoopBoundsBCE,
+  kLoopNullBCE,
+  kBlockBCE,
+  kCHA,
+  kFullFrame,
+  kLast = kFullFrame
+};
+
+inline const char* GetDeoptimizationKindName(DeoptimizationKind kind) {
+  switch (kind) {
+    case DeoptimizationKind::kAotInlineCache: return "AOT inline cache";
+    case DeoptimizationKind::kJitInlineCache: return "JIT inline cache";
+    case DeoptimizationKind::kJitSameTarget: return "JIT same target";
+    case DeoptimizationKind::kLoopBoundsBCE: return "loop bounds check elimination";
+    case DeoptimizationKind::kLoopNullBCE: return "loop bounds check elimination on null";
+    case DeoptimizationKind::kBlockBCE: return "block bounds check elimination";
+    case DeoptimizationKind::kCHA: return "class hierarchy analysis";
+    case DeoptimizationKind::kFullFrame: return "full frame";
+  }
+  LOG(FATAL) << "Unexpected kind " << static_cast<size_t>(kind);
+  UNREACHABLE();
+}
+
+std::ostream& operator<<(std::ostream& os, const DeoptimizationKind& kind);
+
+}  // namespace art
+
+#endif  // ART_RUNTIME_DEOPTIMIZATION_KIND_H_