Remove pt2_quant flag

Summary:
It's been on the to-do list for a while to clean that up.

It's only used in `export_program` to properly put the model in eval mode. Now that we only allow `nn.Module`, there are only two cases: `nn.Module`, which will have `eval()`, and `GraphModule`, which can use `torch.ao.quantization.move_exported_model_to_eval`, which we already called before with the `pt2_quant` flag.

Now that the flag is not needed, remove it everywhere!

We also promote the `quantize_and_export_program` function to `__init__.py` as a compiler API, because it can be quite useful.

Differential Revision: D57491621

backends/cadence/aot/compiler.py

@@ -16,17 +16,18 @@
 
 
 def export_program(
-    model: Callable,
+    model: torch.nn.Module,
     inputs: Any,
     pt2_quant: bool = False,
 ) -> ExportedProgram:
-    # we don't support training mode. Make it eval
+    # We don't support training mode. Make it eval
     if hasattr(model, "eval"):
-        if pt2_quant:
-            # pyre-fixme[6]: Incompatible parameter type.
+        # If the model is already a GraphModule (most likely from quantization),
+        # it can't call eval. Call the suggested torch.ao.quantization API instead,
+        # which only does dropout and batchnorm.
+        if isinstance(model, torch.fx.GraphModule):
             torch.ao.quantization.move_exported_model_to_eval(model)
         else:
-            # pyre-fixme[16]: Anonymous callable has no attribute `eval`.
             model.eval()
 
     # if it's already an ExportedProgram, just return it
@@ -46,11 +47,10 @@ def export_program(
 def export_to_edge(
     model: Callable,
     inputs: Any,
-    pt2_quant: bool = False,
     dump_graphs: bool = False,
 ) -> Tuple[EdgeProgramManager, ExportedProgram]:
     # Export the model into an ExportedProgram.
-    expo_program = export_program(model, inputs, pt2_quant)
+    expo_program = export_program(model, inputs)
 
     if dump_graphs:
         logging.info(f"Exported graph:\n{expo_program.graph_module.graph}")

backends/cadence/aot/export_example.py

@@ -69,9 +69,7 @@ def export_model(
     QuantFusion(patterns)(converted_model)
 
     # Get edge program (note: the name will change to export_to_cadence in future PRs)
-    edge_prog_manager, expo_prog = export_to_edge(
-        converted_model, example_inputs, pt2_quant=True
-    )
+    edge_prog_manager, expo_prog = export_to_edge(converted_model, example_inputs)
 
     # Run a couple required passes for quant/dequant ops
     cadence_prog_manager = edge_prog_manager.transform(