support 0D tensor for paddle.sort/argsort in xpu

paddle/phi/kernels/xpu/argsort_grad_kernel.cc

@@ -17,6 +17,7 @@
 #include "paddle/phi/backends/xpu/enforce_xpu.h"
 #include "paddle/phi/backends/xpu/xpu_context.h"
 #include "paddle/phi/core/kernel_registry.h"
+#include "paddle/phi/kernels/funcs/math_function.h"
 
 namespace phi {
 
@@ -29,6 +30,7 @@ void ArgsortGradKernel(const Context& dev_ctx,
                        bool descending,
                        DenseTensor* in_grad) {
   auto in_dims = indices.dims();
+  auto rank = in_dims.size();
   axis = (axis < 0) ? (in_dims.size() + axis) : axis;
   dev_ctx.template Alloc<T>(in_grad);
 
@@ -40,6 +42,11 @@ void ArgsortGradKernel(const Context& dev_ctx,
 
   if (out_grad.numel() == 0) return;
 
+  if (rank == 0) {
+    phi::funcs::set_constant(dev_ctx, in_grad, 1.0);
+    return;
+  }
+
   bool is_need_transpose = true;
   if (axis == -1 || axis + 1 == in_dims.size()) {
     is_need_transpose = false;

paddle/phi/kernels/xpu/argsort_kernel.cc

@@ -17,6 +17,7 @@
 #include "paddle/phi/backends/xpu/enforce_xpu.h"
 #include "paddle/phi/backends/xpu/xpu_context.h"
 #include "paddle/phi/core/kernel_registry.h"
+#include "paddle/phi/kernels/funcs/math_function.h"
 
 namespace phi {
 
@@ -171,6 +172,7 @@ void ArgsortKernel(const Context& dev_ctx,
                    DenseTensor* output,
                    DenseTensor* indices) {
   auto in_dims = input.dims();
+  auto rank = in_dims.size();
   axis = (axis < 0) ? (in_dims.size() + axis) : axis;
   int n = in_dims[axis];
 
@@ -178,6 +180,12 @@ void ArgsortKernel(const Context& dev_ctx,
   auto output_data = dev_ctx.template Alloc<T>(output);
   auto indices_data = dev_ctx.template Alloc<int64_t>(indices);
 
+  if (rank == 0) {
+    phi::Copy<Context>(dev_ctx, input, dev_ctx.GetPlace(), false, output);
+    phi::funcs::set_constant(dev_ctx, indices, 0);
+    return;
+  }
+
   int len_before = phi::product(phi::slice_ddim(in_dims, 0, axis));
   int len_after =
       phi::product(phi::slice_ddim(in_dims, axis + 1, in_dims.size()));