remove copy of index for gather_nd_grad and scatter_nd_add op in xpu (#51871)

paddle/phi/kernels/xpu/gather_nd_grad_kernel.cc

@@ -65,14 +65,10 @@ void GatherNdGradKernel(const Context &ctx,
   xpu::VectorParam<int64_t> x_vec = {
       x_shape.data(), static_cast<int>(x_shape.size()), nullptr};
 
-  DenseTensor index_cpu(index.type());
-  phi::Copy(ctx, index, phi::CPUPlace(), false, &index_cpu);
-
   int index_size = static_cast<int>(index.numel());
   if (index_type == phi::DataType::INT32) {
     auto index_data = const_cast<int *>(index.data<int>());
-    xpu::VectorParam<int> index_vec{
-        index_cpu.data<int>(), index_size, index_data};
+    xpu::VectorParam<int> index_vec{nullptr, index_size, index_data};
     r = xpu::scatter_nd<T, int>(ctx.x_context(),
                                 nullptr,
                                 out_grad.data<T>(),
@@ -83,8 +79,7 @@ void GatherNdGradKernel(const Context &ctx,
                                 false);
   } else {
     auto index_data = const_cast<int64_t *>(index.data<int64_t>());
-    xpu::VectorParam<int64_t> index_vec{
-        index_cpu.data<int64_t>(), index_size, index_data};
+    xpu::VectorParam<int64_t> index_vec{nullptr, index_size, index_data};
     r = xpu::scatter_nd<T, int64_t>(ctx.x_context(),
                                     nullptr,
                                     out_grad.data<T>(),

paddle/phi/kernels/xpu/scatter_nd_add_kernel.cc

@@ -70,14 +70,11 @@ void ScatterNdAddKernel(const Context &ctx,
   xpu::VectorParam<int64_t> x_vec = {
       x_shape.data(), static_cast<int>(x_shape.size()), nullptr};
 
-  DenseTensor index_cpu(index.type());
-  phi::Copy(ctx, index, phi::CPUPlace(), false, &index_cpu);
-
   int index_size = static_cast<int>(index.numel());
 
   if (index_type == phi::DataType::INT32) {
-    xpu::VectorParam<int> index_vec{index_cpu.data<int>(), index_size, nullptr};
-
+    auto index_data = const_cast<int *>(index.data<int>());
+    xpu::VectorParam<int> index_vec{nullptr, index_size, index_data};
     r = xpu::scatter_nd<T, int>(ctx.x_context(),
                                 nullptr,
                                 updates_ptr,
@@ -87,9 +84,8 @@ void ScatterNdAddKernel(const Context &ctx,
                                 index_shape,
                                 false);
   } else {
-    xpu::VectorParam<int64_t> index_vec{
-        index_cpu.data<int64_t>(), index_size, nullptr};
-
+    auto index_data = const_cast<int64_t *>(index.data<int64_t>());
+    xpu::VectorParam<int64_t> index_vec{nullptr, index_size, index_data};
     r = xpu::scatter_nd<T, int64_t>(ctx.x_context(),
                                     nullptr,
                                     updates_ptr,