[Kernel] Fix fused_gdn_gating (#28343)

Signed-off-by: zjy0516 <riverclouds.zhu@qq.com>

vllm/model_executor/models/qwen3_next.py

@@ -1367,8 +1367,10 @@ def fused_gdn_gating_kernel(
     blk_g = -tl.exp(blk_A_log.to(tl.float32)) * softplus_x
     tl.store(g + off, blk_g.to(g.dtype.element_ty), mask=mask)
     # compute beta_output = sigmoid(b)
-    blk_beta = 1.0 / (1.0 + tl.exp(-blk_b.to(tl.float32)))
-    tl.store(beta_output + off, blk_beta.to(beta_output.dtype.element_ty), mask=mask)
+    blk_beta_output = tl.sigmoid(blk_b.to(tl.float32))
+    tl.store(
+        beta_output + off, blk_beta_output.to(beta_output.dtype.element_ty), mask=mask
+    )
 
 
 def fused_gdn_gating(
@@ -1389,7 +1391,7 @@ def fused_gdn_gating(
     seq_len = 1
     grid = (batch, seq_len, triton.cdiv(num_heads, 8))
     g = torch.empty(1, batch, num_heads, dtype=torch.float32, device=a.device)
-    beta_output = torch.empty(1, batch, num_heads, dtype=torch.float32, device=b.device)
+    beta_output = torch.empty(1, batch, num_heads, dtype=b.dtype, device=b.device)
     fused_gdn_gating_kernel[grid](
         g,
         beta_output,