Add Custom Kernels For LoRA Performance (#1884)

### What this PR does / why we need it?
Add two custom kernels(bgmv_shrink and bgmv expand) to solve the
performance of LoRA
### Does this PR introduce _any_ user-facing change?
no user-facing change
### How was this patch tested?
we add Unit Test file to test the custom ascendc kernel. See
vllm-ascend/tests/e2e/singlecard/ops/test_bgmv_expand.py and
vllm-ascend/tests/e2e/singlecard/ops/test_bgmv_expand.py
Based on the actual test of the QWen2.5 7B model using vllm-ascend
version v0.9.2.rc1, the TTFT, TPOT and throughput have increased by
about 70%.

- vLLM version: v0.9.2
- vLLM main:
40d86ee412

---------

Signed-off-by: taoxudonghaha <justsheldon@163.com>

tests/e2e/singlecard/ops/test_bgmv_expand.py

@@ -0,0 +1,41 @@
+import torch
+
+from vllm_ascend.utils import enable_custom_op
+
+enable_custom_op()
+
+DEFAULT_ATOL = 1e-3
+DEFAULT_RTOL = 1e-3
+
+
+def bgmv_expand_cpu_impl(x: torch.Tensor, w: torch.Tensor,
+                         indices: torch.Tensor, y: torch.tensor,
+                         slice_offset: int, slice_size: int) -> torch.Tensor:
+    W = w[indices, :, :].transpose(-1, -2).to(torch.float32)
+    z = torch.bmm(x.unsqueeze(1).to(torch.float32), W).squeeze()
+    y[:, slice_offset:slice_offset + slice_size] += z
+    return y
+
+
+@torch.inference_mode()
+def test_bgmv_expand() -> None:
+    B = 1
+    x = torch.randn([B, 16], dtype=torch.float)
+    w = torch.randn([64, 128, 16], dtype=torch.float16)
+    indices = torch.zeros([B], dtype=torch.int64)
+    y = torch.randn([B, 128 * 3], dtype=torch.float16)
+
+    x_npu = x.npu()
+    w_npu = w.npu()
+    indices_npu = indices.npu()
+    y_npu = y.npu()
+
+    y_out = bgmv_expand_cpu_impl(x, w, indices, y, 0, 128)
+    y_out_npu = torch.ops._C.bgmv_expand(x_npu, w_npu, indices_npu, y_npu, 0,
+                                         128)
+
+    # Compare the results.
+    torch.testing.assert_close(y_out_npu.cpu(),
+                               y_out,
+                               atol=DEFAULT_ATOL,
+                               rtol=DEFAULT_RTOL)

tests/e2e/singlecard/ops/test_bgmv_shrink.py

@@ -0,0 +1,40 @@
+import torch
+
+from vllm_ascend.utils import enable_custom_op
+
+enable_custom_op()
+
+DEFAULT_ATOL = 1e-3
+DEFAULT_RTOL = 1e-3
+
+
+def bgmv_shrink_cpu_impl(x: torch.Tensor, w: torch.Tensor,
+                         indices: torch.Tensor, y: torch.tensor,
+                         scaling: float) -> torch.Tensor:
+    W = w[indices, :, :].transpose(-1, -2).to(torch.float32)
+    z = torch.bmm(x.unsqueeze(1).to(torch.float32), W).squeeze()
+    y[:, :] += z * scaling
+    return y
+
+
+@torch.inference_mode()
+def test_bgmv_shrink() -> None:
+    B = 1
+    x = torch.randn([B, 128], dtype=torch.float16)
+    w = torch.randn([64, 16, 128], dtype=torch.float16)
+    indices = torch.zeros([B], dtype=torch.int64)
+    y = torch.zeros([B, 16])
+
+    x_npu = x.npu()
+    w_npu = w.npu()
+    indices_npu = indices.npu()
+    y_npu = y.npu()
+
+    y = bgmv_shrink_cpu_impl(x, w, indices, y, 0.5)
+    torch.ops._C.bgmv_shrink(x_npu, w_npu, indices_npu, y_npu, 0.5)
+
+    # Compare the results.
+    torch.testing.assert_close(y_npu.cpu(),
+                               y,
+                               atol=DEFAULT_ATOL,
+                               rtol=DEFAULT_RTOL)