[Kernel] Fix fused_gdn_gating (vllm-project#28343)

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

Author: ZJY0516

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,