[cherry-pick][LITE][XPU] Add xpu softsign kernel (#4860)

test=develop, test=xpu

Author: Cwndmiao

lite/kernels/xpu/activation_compute.cc

@@ -154,6 +154,17 @@ void SignCompute::Run() {
   CHECK_EQ(r, 0);
 }
 
+void SoftsignCompute::Run() {
+  auto& param = this->Param<param_t>();
+  auto& ctx = this->ctx_->As<XPUContext>();
+
+  int r = xdnn::softsign(ctx.GetRawContext(),
+                         param.X->data<float>(),
+                         param.Out->mutable_data<float>(TARGET(kXPU)),
+                         param.X->numel());
+  CHECK_EQ(r, 0);
+}
+
 }  // namespace xpu
 }  // namespace kernels
 }  // namespace lite
@@ -226,3 +237,13 @@ REGISTER_LITE_KERNEL(reciprocal,
     .BindInput("X", {LiteType::GetTensorTy(TARGET(kXPU))})
     .BindOutput("Out", {LiteType::GetTensorTy(TARGET(kXPU))})
     .Finalize();
+
+REGISTER_LITE_KERNEL(softsign,
+                     kXPU,
+                     kFloat,
+                     kNCHW,
+                     paddle::lite::kernels::xpu::SoftsignCompute,
+                     def)
+    .BindInput("X", {LiteType::GetTensorTy(TARGET(kXPU))})
+    .BindOutput("Out", {LiteType::GetTensorTy(TARGET(kXPU))})
+    .Finalize();

lite/kernels/xpu/activation_compute.h

@@ -110,6 +110,15 @@ class SignCompute : public KernelLite<TARGET(kXPU), PRECISION(kFloat)> {
   virtual ~SignCompute() = default;
 };
 
+class SoftsignCompute : public KernelLite<TARGET(kXPU), PRECISION(kFloat)> {
+ public:
+  using param_t = operators::ActivationParam;
+
+  virtual void Run();
+
+  virtual ~SoftsignCompute() = default;
+};
+
 }  // namespace xpu
 }  // namespace kernels
 }  // namespace lite