Track loading happening in parallel with background compilation and abort compilation if necessary.

runtime/vm/isolate.h

Index: runtime/vm/isolate.h
diff --git a/runtime/vm/isolate.h b/runtime/vm/isolate.h
index 8d2508fbd9461f131fad072bc8bd4f1390a5f9a8..5656fc0000cb18b4e5c8373ba0efb84ee1933e80 100644
--- a/runtime/vm/isolate.h
+++ b/runtime/vm/isolate.h
@@ -487,15 +487,11 @@ class Isolate : public BaseIsolate {
     all_classes_finalized_ = value;
   }
 
-  static const uint32_t kInvalidGen = 0;
-
-  void IncrCHAInvalidationGen() {
-    cha_invalidation_gen_++;
-    if (cha_invalidation_gen_ == kInvalidGen) cha_invalidation_gen_++;
-  }
-  void ResetCHAInvalidationGen() { cha_invalidation_gen_ = kInvalidGen; }
-  uint32_t cha_invalidation_gen() const { return cha_invalidation_gen_; }
+  // True during top level parsing.
+  bool top_level_parsing() const { return top_level_parsing_; }
+  void set_top_level_parsing(bool value) { top_level_parsing_ = value; }
 
+  static const uint32_t kInvalidGen = 0;
 
   void IncrFieldInvalidationGen() {
     field_invalidation_gen_++;
@@ -505,12 +501,16 @@ class Isolate : public BaseIsolate {
   void ResetFieldInvalidationGen() { field_invalidation_gen_ = kInvalidGen; }
   uint32_t field_invalidation_gen() const { return field_invalidation_gen_; }
 
-  void IncrPrefixInvalidationGen() {
-    prefix_invalidation_gen_++;
-    if (prefix_invalidation_gen_ == kInvalidGen) prefix_invalidation_gen_++;
+  void IncrLoadingInvalidationGen() {
+    loading_invalidation_gen_++;
+    if (loading_invalidation_gen_ == kInvalidGen) loading_invalidation_gen_++;

[siva, 2016/03/28 17:20:14]

Why are you first incrementing and then checking, won't the check always fail?

Since these values are accessed from another thread, I am wondering if we should
be doing atomic increment operations here.

[srdjan, 2016/03/28 19:54:54]

Since we never reset the count, we may overflow and encounter kInvalidGen again.
Removed unused ResetXXGen.

Yes for atomic operations.

+  }
+  void ResetLoadingInvalidationGen() {
+    loading_invalidation_gen_ = kInvalidGen;
+  }
+  uint32_t loading_invalidation_gen() const {
+    return loading_invalidation_gen_;
   }
-  void ResetPrefixInvalidationGen() { prefix_invalidation_gen_ = kInvalidGen; }
-  uint32_t prefix_invalidation_gen() const { return prefix_invalidation_gen_; }
 
   // Used by background compiler which field became boxed and must trigger
   // deoptimization in the mutator thread.
@@ -720,6 +720,7 @@ class Isolate : public BaseIsolate {
 
   bool compilation_allowed_;
   bool all_classes_finalized_;
+  bool top_level_parsing_;
 
   // Isolate list next pointer.
   Isolate* next_;
@@ -730,9 +731,8 @@ class Isolate : public BaseIsolate {
   // Invalidation generations; used to track events occuring in parallel
   // to background compilation. The counters may overflow, which is OK
   // since we check for equality to detect if an event occured.
-  uint32_t cha_invalidation_gen_;
   uint32_t field_invalidation_gen_;
-  uint32_t prefix_invalidation_gen_;
+  uint32_t loading_invalidation_gen_;
 
   // Protect access to boxed_field_list_.
   Mutex* boxed_field_list_mutex_;