Add support for extended fine grained system memory pool (#1770)

* Add support for extended fine-grained system memory pool
* Use hipHostRegisterUncached
* Add "sc0 sc1" flags for LL store on gfx950
* Update after HIP flag is changed to hipExtHostRegisterUncached

[ROCm/rccl commit: 4640ab19b3]

projects/rccl/src/misc/shmutils.cc

@@ -114,7 +114,11 @@ ncclResult_t ncclShmOpen(char* shmPath, size_t shmPathSize, size_t shmSize, void
   }
 
   if (devShmPtr) {
+#if defined(HIP_HOST_UNCACHED_MEMORY)
+    CUDACHECKGOTO(cudaHostRegister((void*)hptr, realShmSize, cudaHostRegisterPortable | cudaHostRegisterMapped | hipExtHostRegisterUncached), ret, fail);
+#else
     CUDACHECKGOTO(cudaHostRegister((void*)hptr, realShmSize, cudaHostRegisterPortable | cudaHostRegisterMapped), ret, fail);
+#endif
     CUDACHECKGOTO(cudaHostGetDevicePointer(&dptr, (void*)hptr, 0), ret, fail);
   }