refactored emplace_impl to improve inlining

include/boost/unordered/detail/foa.hpp

@@ -1595,9 +1595,26 @@ private:
       };  
     }
     else{
+      return {
+        unchecked_emplace_with_rehash(hash,std::forward<Args>(args)...),
+        true
+      };  
+    }
+  }
+
+  static std::size_t capacity_for(std::size_t n)
+  {
+    return size_policy::size(size_index_for<group_type,size_policy>(n))*N-1;
+  }
+
+  template<typename... Args>
+  BOOST_NOINLINE iterator
+  unchecked_emplace_with_rehash(std::size_t hash,Args&&... args)
+  {
     /* strong exception guarantee -> try insertion before rehash */
     auto     new_arrays_=new_arrays(
                std::size_t(std::ceil(static_cast<float>(size_+1)/mlf)));
+    iterator it;
     BOOST_TRY{
       it=nosize_unchecked_emplace_at(
         new_arrays_,position_for(hash,new_arrays_),
@@ -1612,13 +1629,7 @@ private:
     /* new_arrays_ lifetime taken care of by unchecked_rehash */
     unchecked_rehash(new_arrays_);
     ++size_;
-      return {it,true};
+    return it;
-    }
-  }
-
-  static std::size_t capacity_for(std::size_t n)
-  {
-    return size_policy::size(size_index_for<group_type,size_policy>(n))*N-1;
   }
 
   BOOST_NOINLINE void unchecked_rehash(std::size_t n)