[vm/aot] Minor improvements to make snapshot profiles more useful.

Change-Id: I614d0af3fb3b2bcb642f13d767c385d255b43d5c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/105580
Commit-Queue: Samir Jindel <sjindel@google.com>
Reviewed-by: Ryan Macnak <rmacnak@google.com>

Author: sjindel-google

pkg/vm/lib/v8_snapshot_profile.dart

@@ -46,10 +46,10 @@ const List<String> _kRequiredEdgeFields = [
 ];
 
 class NodeInfo {
-  String type;
-  String name;
-  int id;
-  int selfSize;
+  final String type;
+  final String name;
+  final int id;
+  final int selfSize;
   NodeInfo(
     this.type,
     this.name,
@@ -58,6 +58,16 @@ class NodeInfo {
   );
 }
 
+class EdgeInfo {
+  final int target;
+  final String type;
+
+  // Either a string for property names or an int for array/context elements.
+  final dynamic nameOrIndex;
+
+  EdgeInfo(this.target, this.type, this.nameOrIndex);
+}
+
 class V8SnapshotProfile extends Graph<int> {
   // Indexed by node offset.
   final Map<int, _NodeInfo> _nodes = {};
@@ -265,4 +275,12 @@ class V8SnapshotProfile extends Graph<int> {
     final name = info.name != null ? _strings[info.name] : null;
     return NodeInfo(type, name, info.id, info.selfSize);
   }
+
+  Iterable<EdgeInfo> targets(int node) sync* {
+    for (final _EdgeInfo info in _toEdges[node]) {
+      final String type = _edgeTypes[info.type];
+      yield EdgeInfo(info.nodeOffset, type,
+          type == "property" ? _strings[info.nameOrIndex] : info.nameOrIndex);
+    }
+  }
 }

runtime/vm/v8_snapshot_writer.cc

@@ -31,14 +31,8 @@ V8SnapshotProfileWriter::V8SnapshotProfileWriter(Zone* zone)
   edge_types_.Insert({"element", kElement});
   edge_types_.Insert({"property", kProperty});
   edge_types_.Insert({"internal", kInternal});
-  edge_types_.Insert({"hidden", kHidden});
-  edge_types_.Insert({"shortcut", kShortcut});
-  edge_types_.Insert({"weak", kWeak});
-  edge_types_.Insert({"extra", kExtra});
 
   strings_.Insert({"<unknown>", kUnknownString});
-  strings_.Insert({"<object>", kObjectString});
-  strings_.Insert({"<property>", kPropertyString});
   strings_.Insert({"<artificial root>", kArtificialRootString});
 }
 
@@ -55,11 +49,11 @@ void V8SnapshotProfileWriter::SetObjectTypeAndName(ObjectId object_id,
   intptr_t type_id = node_types_.LookupValue(type);
   ASSERT(info->type == kUnknown || info->type == type_id);
   info->type = type_id;
-
   if (name != nullptr) {
-    info->name = EnsureString(OS::SCreate(zone_, "[%s] %s", type, name));
+    info->name = EnsureString(name);
   } else {
-    info->name = EnsureString(type);
+    info->name =
+        EnsureString(OS::SCreate(zone_, "Unnamed [%s] %s", type, name));
   }
 }
 
@@ -245,7 +239,7 @@ void V8SnapshotProfileWriter::Write(JSONWriter* writer) {
     ObjectIdToNodeInfoTraits::Pair* entry = nullptr;
     auto roots_it = roots_.GetIterator();
     for (int i = 0; (entry = roots_it.Next()) != nullptr; ++i) {
-      WriteEdgeInfo(writer, {kElement, i, entry->key});
+      WriteEdgeInfo(writer, {kInternal, i, entry->key});
     }
 
     auto nodes_it = nodes_.GetIterator();

runtime/vm/v8_snapshot_writer.h

@@ -61,9 +61,7 @@ class V8SnapshotProfileWriter : public ZoneAllocated {
 
   enum ConstantStrings {
     kUnknownString = 0,
-    kPropertyString = 1,
-    kObjectString = 2,
-    kArtificialRootString = 3,
+    kArtificialRootString = 1,
   };
 
 #if !defined(DART_PRECOMPILER)