fix min and max bug (#16570)

test=develop

paddle/fluid/operators/arg_min_max_op_base.h

@@ -58,6 +58,8 @@ class ArgMinMaxKernel : public framework::OpKernel<T> {
     auto& out = *(ctx.Output<framework::LoDTensor>("Out"));
     out.mutable_data<Tout>(ctx.GetPlace());
     auto axis = ctx.Attr<int64_t>("axis");
+    auto x_rank = x.dims().size();
+    if (axis < 0) axis += x_rank;
     auto& dev_ctx = ctx.template device_context<DeviceContext>();
 
 #define CALL_ARG_MINMAX_FUNCTOR(rank)                                \

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

@@ -64,6 +64,14 @@ class TestCase2(BaseTestCase):
         self.axis = 0
 
 
+class TestCase2_1(BaseTestCase):
+    def initTestCase(self):
+        self.op_type = 'arg_max'
+        self.dims = (3, 4)
+        self.dtype = 'int64'
+        self.axis = -1
+
+
 class TestCase3(BaseTestCase):
     def initTestCase(self):
         self.op_type = 'arg_max'