!8863 Fix GatherV2 operator bprop shape problem.

From: @liangchenghui
Reviewed-by: @c_34,@kingxian
Signed-off-by: @c_34,@kingxian

mindspore/ops/_grad/grad_array_ops.py

@@ -351,15 +351,30 @@ def _generate_inverse_index(x_shape, axis):
     return perm
 
 
+@constexpr
+def _regenerate_output_shape(x_shp, ind_shp, axis):
+    rank = len(x_shp)
+    if axis < 0:
+        axis += rank
+    out_shape = x_shp[:axis] + ind_shp + x_shp[axis + 1:]
+    return out_shape
+
+
 @bprop_getters.register(P.GatherV2)
 def get_bprop_gather_v2(self):
     """Generate bprop for GatherV2"""
 
     def bprop(x, indices, axis, out, dout):
+        orig_indices = indices
         if F.rank(dout) == 0:
             dout = P.ExpandDims()(dout, -1)
         if F.rank(indices) == 0:
             indices = P.ExpandDims()(indices, -1)
+            x_shp = shape_op(x)
+            ind_shp = shape_op(indices)
+            out_shp = _regenerate_output_shape(x_shp, ind_shp, axis)
+            dout = reshape(dout, out_shp)
+
         x_shp = shape_op(x)
         out_shp = shape_op(dout)
         ind_shp = shape_op(indices)
@@ -373,7 +388,7 @@ def get_bprop_gather_v2(self):
         # Example: out_shape:(3,2,3) axis 2 -> (1,2,0)
         perm_2 = _generate_inverse_index(x_shp, axis)
         params_grad = transpose(params_grad, perm_2)
-        return params_grad, zeros_like(indices), zeros_like(axis)
+        return params_grad, zeros_like(orig_indices), zeros_like(axis)
 
     return bprop