Add isolate tag-profile and better handling of errors

runtime/vm/tags.cc

Index: runtime/vm/tags.cc
diff --git a/runtime/vm/tags.cc b/runtime/vm/tags.cc
index 84b40f4f24ecfae6bf57aeb2dd06f101c736bf28..f05aa22cc77cf3b478de034d91fd3d78e946f146 100644
--- a/runtime/vm/tags.cc
+++ b/runtime/vm/tags.cc
@@ -5,14 +5,15 @@
 #include "vm/tags.h"
 
 #include "vm/isolate.h"
+#include "vm/json_stream.h"
 
 namespace dart {
 
-const char* VMTag::TagName(uword id) {
-  ASSERT(id != kInvalidTagId);
-  ASSERT(id < kNumVMTags);
-  const TagEntry& entry = entries_[id];
-  ASSERT(entry.id == id);
+const char* VMTag::TagName(uword tag) {
+  ASSERT(tag != kInvalidTagId);
+  ASSERT(tag < kNumVMTags);
+  const TagEntry& entry = entries_[tag];
+  ASSERT(entry.id == tag);
   return entry.name;
 }
 
@@ -41,4 +42,40 @@ VMTagScope::~VMTagScope() {
 }
 
 
+VMTagCounters::VMTagCounters() {
+  for (intptr_t i = 0; i < VMTag::kNumVMTags; i++) {
+    counters_[i] = 0;
+  }
+}
+
+
+void VMTagCounters::Increment(uword tag) {
+  ASSERT(tag != VMTag::kInvalidTagId);
+  ASSERT(tag < VMTag::kNumVMTags);
+  counters_[tag]++;
+}
+
+
+int64_t VMTagCounters::count(uword tag) {
+  ASSERT(tag != VMTag::kInvalidTagId);
+  ASSERT(tag < VMTag::kNumVMTags);
+  return counters_[tag];
+}
+
+
+void VMTagCounters::PrintToJSONObject(JSONObject* obj) {
+  {
+    JSONArray arr(obj, "names");
+    for (intptr_t i = 1; i < VMTag::kNumVMTags; i++) {
+      arr.AddValue(VMTag::TagName(i));
+    }
+  }
+  {
+    JSONArray arr(obj, "counters");
+    for (intptr_t i = 1; i < VMTag::kNumVMTags; i++) {
+      arr.AddValue64(counters_[i]);
+    }
+  }

[turnidge, 2014/03/24 20:22:13]

So you split the message into two parallel arrays?

Efficiency isn't really an issue, given that we have very few tags, so you may
want to consider object-per-tag format for human readability.

Up to you.

[Cutch, 2014/03/25 14:39:06]

I would prefer to keep them as separate arrays. Makes operating on them easier.

+}
+
 }  // namespace dart