Add simple test case

Author: CuiYifeng

test/regressions/test_index_and_index_put.py

@@ -119,3 +119,16 @@ def test_flip_float8(self):
             b_cpu = torch.flip(a_cpu, [0]).to(torch.float32)
             b_xpu = torch.flip(a_xpu, [0]).cpu().to(torch.float32)
             self.assertEqual(b_cpu, b_xpu)
+
+    def test_index_add_empty(self):
+        x_cpu = torch.zeros([128], dtype=torch.int32)
+        idx_cpu = torch.tensor([], dtype=torch.int32)
+        src_cpu = torch.tensor([], dtype=torch.int32)
+        y_cpu = x_cpu.index_add(0, idx_cpu, src_cpu)
+
+        x_xpu = x_cpu.xpu()
+        idx_xpu = idx_cpu.xpu()
+        src_xpu = src_cpu.xpu()
+        y_xpu = x_xpu.index_add(0, idx_xpu, src_xpu)
+
+        self.assertEqual(y_xpu.cpu(), y_cpu)