feat(CRITICAL): 从 GitHub 扫描搬运 ixformer SDK + xllm 完整 GDN/MoE 代码

来源:
  1. Chranos/ixformer (GitHub) → ixformer_sdk/ (230 files, 70K lines)
     - inference/functions/vllm.py: vllm_moe_topk_softmax 完整实现 (2033 lines)
     - inference/functions/moe.py: MoE ops 完整实现 (1380 lines)
     - contrib/vllm_flash_attn/: FA2 Python 接口 (1018 lines)
     - contrib/tgi/fused_moe.py: TGI fused MoE (429 lines)
     - csrc/include/ixformer/: C++ kernel headers + cmake

  2. Deep-Spark/xllm (GitHub) → upstream_ref/xllm_latest/ (+15 files)
     - npu_torch/qwen3_5_decoder_layer_impl.cpp/.h
     - npu_torch/qwen3_5_gated_delta_net.cpp/.h
     - npu_torch/qwen3_next_*.cpp/.h (6 files)
     - npu_torch/attention.cpp/.h + fused_moe.cpp/.h + CMakeLists.txt
     - models/llm/qwen3_5.h + qwen3_5_mtp.h + qwen3_next.h
     - models/vlm/qwen3_5.h

调用链完整性:
  ixformer_sdk/inference/functions/vllm.py
    → ops.infer.moe_topk_softmax() (C++ 层)
    → 这就是 base 镜像 libixformer.so 里的实现

  upstream_ref/xllm_latest/core/layers/ilu/fused_moe.cpp
    → ixformer::infer::topk_softmax() (直接 C++ 调用)
    → ixformer::infer::group_gemm() → 完整 7-step MoE pipeline

ixformer_sdk/contrib/flashinfer/decode.py

@@ -0,0 +1,101 @@
+import math
+from typing import Optional, Tuple, Union
+
+import ixformer.inference.functions as ops
+import torch
+
+
+def _grouped_size_compiled_for_decode_kernels(
+    num_qo_heads: int, num_kv_heads: int
+) -> bool:
+    return (num_qo_heads // num_kv_heads) in [1, 2, 4, 8]
+
+
+class BatchDecodeWithPagedKVCacheWrapper:
+    def __init__(
+        self,
+        float_workspace_buffer: torch.Tensor,
+        kv_layout: str = "NHD",
+        use_cuda_graph: bool = False,
+        use_tensor_cores: bool = False,
+    ) -> None:
+        pass
+
+    def plan(
+        self,
+        indptr: torch.Tensor,
+        indices: torch.Tensor,
+        last_page_len: torch.Tensor,
+        num_qo_heads: int,
+        num_kv_heads: int,
+        head_dim: int,
+        page_size: int,
+        # pos_encoding_mode: str = "NONE",
+        # window_left: int = -1,
+        # logits_soft_cap: Optional[float] = None,
+        data_type: Union[str, torch.dtype] = "float16",
+        q_data_type: Optional[Union[str, torch.dtype]] = None,
+        sm_scale: Optional[float] = None,
+        # rope_scale: Optional[float] = None,
+        # rope_theta: Optional[float] = None,
+        max_seqlen_q: int = None,
+        max_seqlen_k: int = None,
+    ) -> None:
+        self.indptr = indptr
+        self.indices = indices
+        self.last_page_len = last_page_len
+        self.num_qo_heads = num_qo_heads
+        self.num_kv_heads = num_kv_heads
+        self.head_dim = head_dim
+
+        assert page_size == 1
+
+        self.cu_seqlens_q = torch.ones_like(indptr)
+        self.cu_seqlens_q[0] = 0
+        self.cu_seqlens_q = torch.cumsum(self.cu_seqlens_q, dim=0).int()
+
+        self.cu_seqlens_k = indptr
+        if sm_scale is None:
+            sm_scale = 1.0 / math.sqrt(head_dim)
+
+            self.sm_scale = sm_scale
+            self.max_seqlen_q = max_seqlen_q
+            self.max_seqlen_k = max_seqlen_k
+
+    begin_forward = plan
+
+    def forward(
+        self,
+        q: torch.Tensor,
+        paged_kv_cache: Union[torch.Tensor, Tuple[torch.Tensor, torch.Tensor]],
+        pos_encoding_mode: str = "NONE",
+        q_scale: Optional[float] = None,
+        k_scale: Optional[float] = None,
+        v_scale: Optional[float] = None,
+        window_left: int = -1,
+        logits_soft_cap: Optional[float] = None,
+        sm_scale: Optional[float] = None,
+        rope_scale: Optional[float] = None,
+        rope_theta: Optional[float] = None,
+    ) -> torch.Tensor:
+        k_cache, v_cache = paged_kv_cache
+
+        out = torch.empty_like(q)
+
+        ops.paged_attention_flashinfer(
+            output=out,
+            query=q,
+            paged_kv_data=(k_cache.unsqueeze(1), v_cache.unsqueeze(1)),
+            paged_kv_indptr=self.indptr,
+            paged_kv_indices=self.indices,
+            paged_kv_last_page_len=self.last_page_len,
+            scale=self.sm_scale,
+            max_seq_len=self.max_seqlen_k,
+            kv_cache_format="NHD",
+        )
+
+        return out
+
+    def end_forward(self) -> None:
+        r"""Warning: this function is deprecated and has no effect."""
+        pass