[vm] Remove disused Dart_HintFreed.

Uses of this API were replaced with explicit disposal.

TEST=ci
Change-Id: Id6c391c74d77e6a6c6b5b70e446a8abe92294b7a
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/228081
Reviewed-by: Siva Annamalai <asiva@google.com>
Commit-Queue: Ryan Macnak <rmacnak@google.com>

runtime/include/dart_api.h

@@ -1251,18 +1251,6 @@ DART_EXPORT void Dart_EnterIsolate(Dart_Isolate isolate);
  */
 DART_EXPORT void Dart_KillIsolate(Dart_Isolate isolate);
 
-/**
- * Notifies the VM that the embedder expects |size| bytes of memory have become
- * unreachable. The VM may use this hint to adjust the garbage collector's
- * growth policy.
- *
- * Multiple calls are interpreted as increasing, not replacing, the estimate of
- * unreachable memory.
- *
- * Requires there to be a current isolate.
- */
-DART_EXPORT void Dart_HintFreed(intptr_t size);
-
 /**
  * Notifies the VM that the embedder expects to be idle until |deadline|. The VM
  * may use this time to perform garbage collection or other tasks to avoid

runtime/vm/dart_api_impl.cc

@@ -1811,17 +1811,6 @@ DART_EXPORT Dart_Handle Dart_GetStickyError() {
   return Api::NewHandle(T, I->sticky_error());
 }
 
-DART_EXPORT void Dart_HintFreed(intptr_t size) {
-  if (size < 0) {
-    FATAL1("%s requires a non-negative size", CURRENT_FUNC);
-  }
-  Thread* T = Thread::Current();
-  CHECK_ISOLATE(T->isolate());
-  API_TIMELINE_BEGIN_END(T);
-  TransitionNativeToVM transition(T);
-  T->heap()->HintFreed(size);
-}
-
 DART_EXPORT void Dart_NotifyIdle(int64_t deadline) {
   Thread* T = Thread::Current();
   CHECK_ISOLATE(T->isolate());

runtime/vm/dart_api_impl_test.cc

@@ -9525,39 +9525,6 @@ TEST_CASE(DartAPI_TimelineCategories) {
   }
 }
 
-static void HintFreedNative(Dart_NativeArguments args) {
-  int64_t size = 0;
-  EXPECT_VALID(Dart_GetNativeIntegerArgument(args, 0, &size));
-  Dart_HintFreed(size);
-}
-
-static Dart_NativeFunction HintFreed_native_lookup(Dart_Handle name,
-                                                   int argument_count,
-                                                   bool* auto_setup_scope) {
-  return HintFreedNative;
-}
-
-TEST_CASE(DartAPI_HintFreed) {
-  const char* kScriptChars = R"(
-@pragma("vm:external-name", "Test_nativeFunc")
-external void hintFreed(int size);
-void main() {
-  var v;
-  for (var i = 0; i < 100; i++) {
-    var t = [];
-    for (var j = 0; j < 10000; j++) {
-      t.add(List.filled(100, null));
-    }
-    v = t;
-    hintFreed(100 * 10000 * 4);
-  }
-})";
-  Dart_Handle lib =
-      TestCase::LoadTestScript(kScriptChars, &HintFreed_native_lookup);
-  Dart_Handle result = Dart_Invoke(lib, NewString("main"), 0, NULL);
-  EXPECT_VALID(result);
-}
-
 static void NotifyIdleShortNative(Dart_NativeArguments args) {
   Dart_NotifyIdle(Dart_TimelineGetMicros() + 10 * kMicrosecondsPerMillisecond);
 }

runtime/vm/heap/heap.cc

@@ -356,10 +356,6 @@ ObjectPtr Heap::FindObject(FindObjectVisitor* visitor) {
   return raw_obj;
 }
 
-void Heap::HintFreed(intptr_t size) {
-  old_space_.HintFreed(size);
-}
-
 void Heap::NotifyIdle(int64_t deadline) {
   Thread* thread = Thread::Current();
   TIMELINE_FUNCTION_GC_DURATION(thread, "NotifyIdle");

runtime/vm/heap/heap.h

@@ -104,7 +104,6 @@ class Heap {
   ObjectPtr FindNewObject(FindObjectVisitor* visitor);
   ObjectPtr FindObject(FindObjectVisitor* visitor);
 
-  void HintFreed(intptr_t size);
   void NotifyIdle(int64_t deadline);
   void NotifyLowMemory();
 

runtime/vm/heap/pages.cc

@@ -1692,17 +1692,6 @@ void PageSpaceController::RecordUpdate(SpaceUsage before,
   }
 }
 
-void PageSpaceController::HintFreed(intptr_t size) {
-  intptr_t size_in_words = size << kWordSizeLog2;
-  if (size_in_words > idle_gc_threshold_in_words_) {
-    idle_gc_threshold_in_words_ = 0;
-  } else {
-    idle_gc_threshold_in_words_ -= size_in_words;
-  }
-
-  // TODO(rmacnak): Hasten the soft threshold at some discount?
-}
-
 void PageSpaceGarbageCollectionHistory::AddGarbageCollectionTime(int64_t start,
                                                                  int64_t end) {
   Entry entry;

runtime/vm/heap/pages.h

@@ -265,7 +265,6 @@ class PageSpaceController {
                                  int64_t start,
                                  int64_t end);
   void EvaluateAfterLoading(SpaceUsage after);
-  void HintFreed(intptr_t size);
 
   void set_last_usage(SpaceUsage current) { last_usage_ = current; }
 
@@ -359,7 +358,6 @@ class PageSpace {
   void EvaluateAfterLoading() {
     page_space_controller_.EvaluateAfterLoading(usage_);
   }
-  void HintFreed(intptr_t size) { page_space_controller_.HintFreed(size); }
 
   int64_t UsedInWords() const { return usage_.used_in_words; }
   int64_t CapacityInWords() const {