skip bf16 test if not supported (#42503)

python/paddle/fluid/tests/unittests/test_imperative_auto_mixed_precision.py

@@ -1254,9 +1254,8 @@ class TestBf16(unittest.TestCase):
 
     def test_bf16(self):
         def func_isinstance():
-            if fluid.core.is_compiled_with_cuda():
-                cudnn_version = paddle.device.get_cudnn_version()
-                if cudnn_version is not None and cudnn_version >= 8100:
+            if fluid.core.is_compiled_with_cuda(
+            ) and fluid.core.is_bfloat16_supported(paddle.CUDAPlace(0)):
                 out_fp32 = self.train(enable_amp=False)
                 out_bf16_O1 = self.train(enable_amp=True, amp_level='O1')
                 out_bf16_O2 = self.train(enable_amp=True, amp_level='O2')