[CustomDevice] refine set_constant_with_place by calling full kernel (#55089)

paddle/phi/kernels/funcs/math_function.cc

@@ -34,6 +34,10 @@ limitations under the License. */
 #include "paddle/phi/kernels/funcs/eigen/common.h"
 #include "paddle/phi/kernels/funcs/math_function_impl.h"
 #include "unsupported/Eigen/CXX11/Tensor"
+#ifdef PADDLE_WITH_CUSTOM_DEVICE
+#include "paddle/phi/api/lib/kernel_dispatch.h"
+#include "paddle/phi/core/kernel_factory.h"
+#endif
 
 namespace phi {
 namespace funcs {
@@ -171,16 +175,27 @@ void set_constant_with_place<phi::IPUPlace>(const phi::DeviceContext& context,
 template <>
 void set_constant_with_place<phi::CustomPlace>(
     const phi::DeviceContext& context, phi::DenseTensor* tensor, float value) {
-  phi::DenseTensor tmp_tensor;
-  tmp_tensor.Resize(tensor->dims());
-  context.HostAlloc(&tmp_tensor, tensor->dtype());
-  phi::VisitDataType(tmp_tensor.dtype(),
-                     TensorSetConstantCPU(&tmp_tensor, value));
-  phi::memory_utils::Copy(tensor->place(),
-                          tensor->data(),
-                          phi::CPUPlace(),
-                          tmp_tensor.data(),
-                          tensor->numel() * phi::SizeOf(tensor->dtype()));
+#ifdef PADDLE_WITH_CUSTOM_DEVICE
+  auto kernel_result = phi::KernelFactory::Instance().SelectKernelOrThrowError(
+      "full",
+      {paddle::experimental::ParseBackend(tensor->place()),
+       phi::DataLayout::ALL_LAYOUT,
+       paddle::experimental::ParseDataType(tensor->dtype())});
+  const auto& kernel = kernel_result.kernel;
+  using kernel_signature = void (*)(const phi::DeviceContext&,
+                                    const phi::IntArray&,
+                                    const phi::Scalar&,
+                                    DataType,
+                                    phi::DenseTensor*);
+  auto* kernel_fn = kernel.GetVariadicKernelFn<kernel_signature>();
+  (*kernel_fn)(context,
+               phi::IntArray(phi::vectorize(tensor->dims())),
+               phi::Scalar(value),
+               tensor->dtype(),
+               tensor);
+#else
+  PADDLE_THROW(phi::errors::Unimplemented("CustomPlace is not supported"));
+#endif
 }
 
 template <>