Cache value of "non-nullable" flag so it can be used in the VM code without having to search through the array of experimental flags array.

Change-Id: I297dca48711ef2bdd80a102086dea1bb075ea357
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/125081
Reviewed-by: Régis Crelier <regis@google.com>
Commit-Queue: Siva Annamalai <asiva@google.com>

Author: a-siva

runtime/vm/dart.cc

@@ -69,6 +69,7 @@ Dart_FileReadCallback Dart::file_read_callback_ = NULL;
 Dart_FileWriteCallback Dart::file_write_callback_ = NULL;
 Dart_FileCloseCallback Dart::file_close_callback_ = NULL;
 Dart_EntropySource Dart::entropy_source_callback_ = NULL;
+bool Dart::non_nullable_flag_ = false;
 
 // Structure for managing read-only global handles allocation used for
 // creating global read-only handles that are pre created and initialized
@@ -222,6 +223,9 @@ char* Dart::Init(const uint8_t* vm_isolate_snapshot,
     ASSERT(Flags::Initialized());
     const bool is_vm_isolate = true;
 
+    // Cache value of "non-nullable" experimental flag.
+    set_non_nullable_flag(KernelIsolate::GetExperimentalFlag("non-nullable"));
+
     // Setup default flags for the VM isolate.
     Dart_IsolateFlags api_flags;
     Isolate::FlagsInitialize(&api_flags);

runtime/vm/dart.h

@@ -123,6 +123,8 @@ class Dart : public AllStatic {
   static Dart_EntropySource entropy_source_callback() {
     return entropy_source_callback_;
   }
+  static void set_non_nullable_flag(bool value) { non_nullable_flag_ = value; }
+  static bool non_nullable_flag() { return non_nullable_flag_; }
 
  private:
   static void WaitForIsolateShutdown();
@@ -141,6 +143,7 @@ class Dart : public AllStatic {
   static Dart_FileWriteCallback file_write_callback_;
   static Dart_FileCloseCallback file_close_callback_;
   static Dart_EntropySource entropy_source_callback_;
+  static bool non_nullable_flag_;
 };
 
 }  // namespace dart

runtime/vm/object.cc

@@ -8244,7 +8244,7 @@ bool Function::CheckSourceFingerprint(const char* prefix, int32_t fp) const {
     return true;
   }
 
-  if (KernelIsolate::GetExperimentalFlag("non-nullable")) {
+  if (Dart::non_nullable_flag()) {
     // The non-nullable experiment changes the fingerprints, and we only track
     // one fingerprint set.
     return true;