[vm] Enable non-nullable experiment when building platform dill with --nnbd flag.

Change-Id: I00632cc2dcf5e929698ee6b88eefbd5c58752297
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/122174
Commit-Queue: Liam Appelbe <liama@google.com>
Reviewed-by: Ryan Macnak <rmacnak@google.com>
Reviewed-by: Alexander Markov <alexmarkov@google.com>

Author: liamappelbe

runtime/bin/BUILD.gn

@@ -4,6 +4,7 @@
 
 import("../../build/config/gclient_args.gni")
 import("../../build/dart/dart_action.gni")
+import("../../sdk_args.gni")
 import("../runtime_args.gni")
 import("../vm/compiler/compiler_sources.gni")
 import("../vm/heap/heap_sources.gni")
@@ -537,7 +538,11 @@ gen_snapshot_action("generate_snapshot_bin") {
     isolate_snapshot_data,
     isolate_snapshot_instructions,
   ]
-  args = [
+  args = []
+  if (use_nnbd) {
+    args += [ "--enable-experiment=non-nullable" ]
+  }
+  args += [
     "--deterministic",
     "--snapshot_kind=" + dart_core_snapshot_kind,
     "--vm_snapshot_data=" + rebase_path(vm_snapshot_data, root_build_dir),

runtime/vm/BUILD.gn

@@ -16,6 +16,7 @@ import("../../sdk/lib/mirrors/mirrors_sources.gni")
 import("../../sdk/lib/typed_data/typed_data_sources.gni")
 import("../../sdk/lib/vmservice/vmservice_sources.gni")
 import("../../sdk/lib/wasm/wasm_sources.gni")
+import("../../sdk_args.gni")
 import("../../utils/compile_platform.gni")
 import("../bin/cli_sources.gni")
 import("../bin/io_sources.gni")
@@ -146,6 +147,9 @@ template("gen_vm_platform") {
       "-Ddart.developer.causal_async_stacks=$allow_causal_async_stacks",
       "-Ddart.isVM=true",
     ]
+    if (use_nnbd) {
+      args += [ "--enable-experiment=non-nullable" ]
+    }
     if (defined(invoker.exclude_source) && invoker.exclude_source) {
       args += [ "--exclude-source" ]
     }

runtime/vm/kernel_isolate.cc

@@ -395,6 +395,15 @@ void KernelIsolate::AddExperimentalFlag(const char* value) {
   experimental_flags_->Add(strdup(value));
 }
 
+bool KernelIsolate::GetExperimentalFlag(const char* value) {
+  for (const char* str : *experimental_flags_) {
+    if (strcmp(str, value) == 0) {
+      return true;
+    }
+  }
+  return false;
+}
+
 DEFINE_OPTION_HANDLER(KernelIsolate::AddExperimentalFlag,
                       enable_experiment,
                       "Comma separated list of experimental features.");

runtime/vm/kernel_isolate.h

@@ -69,6 +69,7 @@ class KernelIsolate : public AllStatic {
   static void NotifyAboutIsolateShutdown(const Isolate* isolate);
 
   static void AddExperimentalFlag(const char* value);
+  static bool GetExperimentalFlag(const char* value);
 
  protected:
   static void InitCallback(Isolate* I);

runtime/vm/object.cc

@@ -8210,6 +8210,12 @@ bool Function::CheckSourceFingerprint(const char* prefix, int32_t fp) const {
     return true;
   }
 
+  if (KernelIsolate::GetExperimentalFlag("non-nullable")) {
+    // The non-nullable experiment changes the fingerprints, and we only track
+    // one fingerprint set.
+    return true;
+  }
+
   if (SourceFingerprint() != fp) {
     const bool recalculatingFingerprints = false;
     if (recalculatingFingerprints) {