Subzero: Fixed deadlock with _start but no globals

src/IceInstrumentation.h

Index: src/IceInstrumentation.h
diff --git a/src/IceInstrumentation.h b/src/IceInstrumentation.h
index 32979634a9f363508bed7abb8025544c1de47a09..dcc116686f3ed7f40fa4f14d5eb6edc9829433b9 100644
--- a/src/IceInstrumentation.h
+++ b/src/IceInstrumentation.h
@@ -43,9 +43,11 @@ public:
   Instrumentation(GlobalContext *Ctx) : Ctx(Ctx) {}
   virtual void instrumentGlobals(VariableDeclarationList &) {}
   void instrumentFunc(Cfg *Func);
+  void setHasSeenGlobals();
 
 protected:
   virtual void instrumentInst(LoweringContext &Context);
+  LockedPtr<VariableDeclarationList> getGlobals();
 
 private:
   virtual bool isInstrumentable(Cfg *) { return true; }
@@ -78,6 +80,11 @@ private:
 
 protected:
   GlobalContext *Ctx;
+
+private:
+  bool HasSeenGlobals = false;
+  std::mutex GlobalsSeenMutex;
+  std::condition_variable GlobalsSeenCV;
 };
 
 } // end of namespace Ice