Subzero: Fixed deadlock with _start but no globals

src/IceGlobalContext.h

Index: src/IceGlobalContext.h
diff --git a/src/IceGlobalContext.h b/src/IceGlobalContext.h
index 2d60f4845466f879ebc50a407ca021edab29a01f..4788423ec988bba9f296ed6513e129c048d0fbb4 100644
--- a/src/IceGlobalContext.h
+++ b/src/IceGlobalContext.h
@@ -482,6 +482,12 @@ public:
     return LockedPtr<StringPool>(Strings.get(), &StringsLock);
   }
 
+  LockedPtr<VariableDeclarationList> getGlobals() {
+    return LockedPtr<VariableDeclarationList>(&Globals, &InitAllocLock);
+  }
+
+  bool getGlobalsReceived() { return GlobalsReceived; }
+
   /// Number of function blocks that can be queued before waiting for
   /// translation
   /// threads to consume.
@@ -500,6 +506,7 @@ private:
   // Managed by getInitializerAllocator()
   mutable GlobalLockType InitAllocLock;
   VariableDeclarationList Globals;
+  std::atomic<bool> GlobalsReceived;
 
   ICE_CACHELINE_BOUNDARY;
   // Managed by getDestructors()
@@ -612,6 +619,7 @@ private:
     LockedPtr<VariableDeclarationList> _(&Globals, &InitAllocLock);
     if (Globls != nullptr) {
       Globals.merge(Globls.get());
+      GlobalsReceived = true;
     }
   }