Integrated RCCL with MSCCL++ for small message sizes (#1231)

[ROCm/rccl commit: 6dc47eecd7]

projects/rccl/src/include/comm.h

@@ -393,6 +393,13 @@ struct ncclComm {
   // shared structures for finalization
   int finalizeRankCnt;
 
+#if defined(ENABLE_MSCCLPP)
+  // Whether this comm is compatible with MSCCLPP
+  bool mscclppCompatible;
+  struct mscclpp_ncclComm* mscclpp_comm;
+  size_t mscclpp_threshold;
+#endif
+
   // Whether this comm is compatible with MSCCL
   bool mscclCompatible;
   // group job to support multi-thread FT