Remove leftover implementations for optional userbuffers support (#932)

* Remove optional UB build leftovers
Signed-off-by: Kirthi Shankar Sivamani <ksivamani@nvidia.com>

* rm unused import
Signed-off-by: Kirthi Shankar Sivamani <ksivamani@nvidia.com>

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci



---------
Signed-off-by: Kirthi Shankar Sivamani <ksivamani@nvidia.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

transformer_engine/pytorch/csrc/extensions.h

@@ -368,8 +368,6 @@ size_t get_cublasLt_version();
 
 size_t get_cudnn_version();
 
-void placeholder();
-
 /***************************************************************************************************
  * Support THD format for Context Parallel
  **************************************************************************************************/

transformer_engine/pytorch/csrc/extensions/misc.cu

@@ -5,12 +5,7 @@
  ************************************************************************/
 
 #include "extensions.h"
-#ifdef NVTE_WITH_USERBUFFERS
-#include "comm_gemm_overlap.h"
-#endif  // NVTE_WITH_USERBUFFERS
 
 size_t get_cublasLt_version() { return cublasLtGetVersion(); }
 
 size_t get_cudnn_version() { return cudnnGetVersion(); }
-
-void placeholder() {}  // TODO(ksivamani) clean this up

transformer_engine/pytorch/transformer.py

@@ -10,7 +10,6 @@ from typing import Callable, List, Optional, Tuple, Union
 
 import torch
 
-import transformer_engine_torch as tex
 from transformer_engine.pytorch.module import LayerNormMLP, LayerNorm, RMSNorm
 from transformer_engine.pytorch.attention import (
     InferenceParams,
@@ -270,9 +269,6 @@ class TransformerLayer(torch.nn.Module):
     ) -> None:
         super().__init__()
 
-        if ub_tp_comm_overlap:
-            assert tex.userbuf_comm_available(), "Userbuffer communication backend not available."
-
         self.self_attn_mask_type = self_attn_mask_type
         self.window_size = window_size
         self.window_size = check_set_window_size(self_attn_mask_type, self.window_size)