Enable quantization for mobilebert (#477)

Summary:
Pull Request resolved: #477

Quantized: https://www.internalfb.com/intern/everpaste/?handle=GDQbkxamK5wUoYUDALGrDOPik_tUbsIXAAAB

didn't check against fx since the model is not symbolically traceable

Reviewed By: cccclai

Differential Revision: D49379415

fbshipit-source-id: 57c6361120d1bea6c58f3dad806eb57f3fef3b29

Author: jerryzh168

examples/quantization/example.py

@@ -43,8 +43,9 @@
 def verify_xnnpack_quantizer_matching_fx_quant_model(model_name, model, example_inputs):
     """This is a verification against fx graph mode quantization flow as a sanity check"""
 
-    if model_name == "edsr":
+    if model_name in ["edsr", "mobilebert"]:
         # EDSR has control flows that are not traceable in symbolic_trace
+        # mobilebert is not symbolically traceable with torch.fx.symbolic_trace
         return
     if model_name == "ic3":
         # we don't want to compare results of inception_v3 with fx, since mul op with Scalar

examples/recipes/xnnpack_optimization/models.py

@@ -27,4 +27,5 @@ class OptimizationOptions(object):
     "vit": OptimizationOptions(False, True),
     "w2l": OptimizationOptions(False, True),
     "edsr": OptimizationOptions(True, False),
+    "mobilebert": OptimizationOptions(True, False),
 }