Add instruction tags to saved ICData (debug mode only).

runtime/platform/globals.h

Index: runtime/platform/globals.h
diff --git a/runtime/platform/globals.h b/runtime/platform/globals.h
index 82f5719e31a7264d63583f9c359e6a3cd43a4ae8..7e11bb3163e548452ce260bd0fb8be1ad1214f0d 100644
--- a/runtime/platform/globals.h
+++ b/runtime/platform/globals.h
@@ -650,6 +650,14 @@ static inline T ReadUnaligned(const T* ptr) {
 #define STDERR_FILENO 2
 #endif
 
+// For checking deterministic graph generation, we can store instruction
+// tag in the ICData and check it when recreating the flow graph in
+// optimizing compiler. Enable it for other modes (product, release) if needed
+// for debugging.
+#if defined(DEBUG)
+#define TAG_IC_DATA
+#endif
+
 }  // namespace dart
 
 #endif  // PLATFORM_GLOBALS_H_