Fix float64 bug in layer norm (#30452)

built-in `rsqrt` is shadowed

paddle/fluid/operators/layer_norm_op.cu

@@ -108,23 +108,23 @@ struct PairForLayerNormAddFunctor {
 };
 
 template <typename T>
-__inline__ __device__ T rsqrt(const T val) {
+__inline__ __device__ T rsqrt_(const T val) {
   return static_cast<T>(1) / sqrt(val);
 }
 
 template <>
-__inline__ __device__ float rsqrt(const float val) {
+__inline__ __device__ float rsqrt_(const float val) {
   return rsqrtf(val);
 }
 
 template <>
-__inline__ __device__ double rsqrt(const double val) {
+__inline__ __device__ double rsqrt_(const double val) {
   return rsqrt(val);
 }
 
 #if CUDA_ARCH_FP16_SUPPORTED(__CUDA_ARCH__)
 template <>
-__inline__ __device__ half rsqrt(const half val) {
+__inline__ __device__ half rsqrt_(const half val) {
   return hrsqrt(val);
 }
 #endif
@@ -161,7 +161,7 @@ __global__ void LayerNormForward(const T *x, const U *scale, const U *bias,
   __syncthreads();
 
   mean_val = mean_share;
-  U invvar = rsqrt<U>(var_share + static_cast<U>(epsilon));
+  U invvar = rsqrt_<U>(var_share + static_cast<U>(epsilon));
 
   // Step 2: Calculate y
   if (scale != nullptr) {
@@ -204,7 +204,7 @@ __inline__ __device__ void cuLoadAddStridedInputs(
   const int i1 = i1_block + thr_load_row_off;
   if (i1 >= i1_end) return;
   U curr_mean = mean[i1];
-  U curr_invvar = rsqrt<U>(var[i1] + epsilon);
+  U curr_invvar = rsqrt_<U>(var[i1] + epsilon);
   for (int k = 0; k < VPT; ++k) {
     const int i2 = i2_off + k;
     const int load_idx = i1 * n2 + i2;
@@ -352,7 +352,7 @@ __global__ void LayerNormBackwardComputeGradInput(
     U sum_loss1 = U(0);
     U sum_loss2 = U(0);
     const U c_mean = mean[i1];
-    const U c_invvar = rsqrt<U>(var[i1] + epsilon);
+    const U c_invvar = rsqrt_<U>(var[i1] + epsilon);
     const T *k_input = input + i1 * n2;
     const T *k_dout = dout + i1 * n2;
     constexpr int numx = BDIMX * BDIMY;