[Hardware][Intel GPU] Add Intel GPU(XPU) inference backend (#3814)

Co-authored-by: Jiang Li <jiang1.li@intel.com>
Co-authored-by: Abhilash Majumder <abhilash.majumder@intel.com>
Co-authored-by: Abhilash Majumder <30946547+abhilash1910@users.noreply.github.com>

vllm/model_executor/layers/layernorm.py

@@ -67,6 +67,30 @@ class RMSNorm(CustomOp):
         )
         return out
 
+    def forward_xpu(
+        self,
+        x: torch.Tensor,
+        residual: Optional[torch.Tensor] = None,
+    ) -> Union[torch.Tensor, Tuple[torch.Tensor, torch.Tensor]]:
+        from vllm._ipex_ops import ipex_ops as ops
+
+        if residual is not None:
+            ops.fused_add_rms_norm(
+                x,
+                residual,
+                self.weight.data,
+                self.variance_epsilon,
+            )
+            return x, residual
+        out = torch.empty_like(x)
+        ops.rms_norm(
+            out,
+            x,
+            self.weight.data,
+            self.variance_epsilon,
+        )
+        return out
+
     def extra_repr(self) -> str:
         s = f"hidden_size={self.weight.data.size(0)}"
         s += f", eps={self.variance_epsilon}"