Add SwigluOAI implementation for CPUFusedMOE (#26347)

Signed-off-by: Sharif Inamdar <sharif.inamdar@arm.com>

vllm/model_executor/layers/fused_moe/cpu_fused_moe.py

@@ -13,6 +13,17 @@ def silu_and_mul(x: torch.Tensor) -> torch.Tensor:
     return F.silu(x[..., :d]) * x[..., d:]
 
 
+def swigluoai_and_mul(
+    x: torch.Tensor, alpha: float = 1.702, limit: float = 7.0
+) -> torch.Tensor:
+    d = x.shape[-1] // 2
+    gate, up = x[..., :d], x[..., d:]
+    gate = gate.clamp(max=limit)
+    up = up.clamp(min=-limit, max=limit)
+    glu = gate * torch.sigmoid(alpha * gate)
+    return (up + 1) * glu
+
+
 def grouped_topk(
     hidden_states: torch.Tensor,
     gating_output: torch.Tensor,
@@ -247,7 +258,7 @@ class CPUFusedMOE:
         apply_router_weight_on_input: bool = False,
         activation: str = "silu",
     ) -> torch.Tensor:
-        assert activation == "silu", f"{activation} is not supported."
+        assert activation in {"silu", "swigluoai"}, f"{activation} is not supported."
         assert not apply_router_weight_on_input
         topk_weights, topk_ids = select_experts(
             hidden_states=x,
@@ -293,7 +304,10 @@ class CPUFusedMOE:
             gate_up = F.linear(
                 tokens_for_this_expert, layer_w13_weight, bias=layer_w13_bias
             )
-            gate_up = silu_and_mul(gate_up)
+            if activation == "swigluoai":
+                gate_up = swigluoai_and_mul(gate_up)
+            else:
+                gate_up = silu_and_mul(gate_up)
             expert_out = F.linear(gate_up, layer_w2_weight, bias=layer_w2_bias)
             outputs.append(expert_out)
             start_idx = end_idx