[Perf][Moe]improve cutlass_moe_fp4 performance by using apply_router_weight_on_i… (#19493)

python/sglang/srt/layers/moe/cutlass_moe.py

@@ -491,10 +491,12 @@ def cutlass_moe_fp4(
         params.to_gemm2_args(),
     )
     del int_fp4, int_blockscale
-    c2 = shuffle_rows(c2, c_map, (m_a * num_topk, params.hidden_size))
-    c2 = c2.view(m_a, num_topk, params.hidden_size)
+
     if no_combine:
+        c2 = shuffle_rows(c2, c_map, (m_a * num_topk, params.hidden_size))
+        c2 = c2.view(m_a, num_topk, params.hidden_size)
         return c2.to(out_dtype)
-    if not apply_router_weight_on_input:
-        c2 = c2 * topk_weights.view(m_a, num_topk, 1).to(out_dtype)
-    return c2.sum(dim=1).to(out_dtype)
+    output = torch.empty((m_a, k_a), device=device, dtype=out_dtype)
+    weights = topk_weights.to(out_dtype) if not apply_router_weight_on_input else None
+    apply_shuffle_mul_sum(c2, output, c_map, weights)
+    return output