[0-size Tensor No. 233、238、276、281 、324] Add 0-size Tensor support for zeropad2d、nonzero、__getitem__、__setitem__ API (PaddlePaddle#74057)

* fix nonzero dtype error

* fix __geitem__ and zeropad2d

* add zeropad2d unittest

Author: DanielSun11

paddle/phi/kernels/cpu/nonzero_kernel.cc

@@ -56,7 +56,7 @@ void NonZeroKernel(const Context& dev_ctx,
   const int rank = dims.size();
 
   if (numel == 0) {
-    dev_ctx.template Alloc<T>(out);
+    dev_ctx.template Alloc<int64_t>(out);
     return;
   }
 

paddle/phi/kernels/gpu/gather_grad_kernel.cu

@@ -31,7 +31,7 @@ void GatherGradKernel(const Context& dev_ctx,
                       const Scalar& axis,
                       DenseTensor* x_grad) {
   // x [4, 2], index [2, 0], out [2, 0], x_grad [4, 2]
-  if (out_grad.numel() == 0) {
+  if (out_grad.numel() == 0 || (x_grad && x_grad->numel() == 0)) {
     if (x_grad) {
       phi::Full<T, Context>(
           dev_ctx, phi::IntArray(common::vectorize(x_grad->dims())), 0, x_grad);

paddle/phi/kernels/gpu/nonzero_kernel.cu

@@ -66,7 +66,7 @@ void NonZeroKernel(const Context &dev_ctx,
                    const DenseTensor &condition,
                    DenseTensor *out) {
   if (condition.numel() == 0) {
-    dev_ctx.template Alloc<T>(out);
+    dev_ctx.template Alloc<int64_t>(out);
     return;
   }
   DenseTensor in_data;

paddle/phi/kernels/gpu/pad3d_grad_kernel.cu

@@ -690,6 +690,8 @@ PD_REGISTER_KERNEL(pad3d_grad,
                    phi::Pad3dGradKernel,
                    float,
                    double,
+                   int,
+                   int64_t,
                    phi::dtype::float16,
                    phi::dtype::bfloat16,
                    phi::dtype::complex<float>,

paddle/phi/kernels/xpu/nonzero_kernel.cc

@@ -33,7 +33,7 @@ void NonZeroKernel(const Context& dev_ctx,
   using XPUType = typename XPUTypeTrait<T>::Type;
 
   if (numel == 0) {
-    dev_ctx.template Alloc<T>(out);
+    dev_ctx.template Alloc<int64_t>(out);
     return;
   }
 

test/legacy_test/test_zeropad2d.py

@@ -112,6 +112,19 @@ def test_support_pad4(self):
         ret_res = zeropad2d(x_tensor, pad_tensor).numpy()
         np.testing.assert_allclose(expect_res, ret_res, rtol=1e-05)
 
+    def test_support_pad5(self):
+        """
+        test the zero size Tensor.
+        """
+        pad = (1, 2, 3, 4)
+        x = np.random.randint(-255, 255, size=[0, 2, 3])
+        x_tensor = to_tensor(x, stop_gradient=False)
+        ret_res = zeropad2d(x_tensor, pad)
+        ret_res.backward()
+        np.testing.assert_allclose(
+            x_tensor.shape, x_tensor.grad.shape, rtol=1e-05
+        )
+
 
 class TestZeroPad2DLayer(unittest.TestCase):
     """