Add small repro test for unsigned -> signed et loss error (#8506)

Summary:

There was a difference in behavior from `quantized_decomposed.quantize_per_tensor`
and `cadence.quantize_per_tensor`, specifically how rounding half values worked.
The former rounds towards even (based on `torch.round` which does that).
The latter rounds away from zero.

Make sure the python implementation matches the Executorch implementation in this
regard.

Reviewed By: sabarishsnk

Differential Revision: D69668881

Author: dulinriley

backends/cadence/aot/TARGETS

@@ -180,6 +180,7 @@ python_library(
     typing = True,
     deps = [
         "//caffe2:torch",
+        ":ops_registrations",
         ":compiler_utils",
         "//executorch/backends/cadence/aot:pass_utils",
         "//executorch/backends/cadence/aot:utils",

backends/cadence/aot/fuse_ops.py

@@ -16,6 +16,9 @@
 from numbers import Number
 from typing import cast, Sequence
 
+# Import these for the cadence function signatures.
+import executorch.backends.cadence.aot.ops_registrations # noqa: F401
+
 import torch
 import torch.fx
 from executorch.backends.cadence.aot.compiler_utils import (
@@ -849,7 +852,10 @@ def attempt_fusion(
             if isinstance(arg, torch.fx.Node)
             and isinstance(arg.target, EdgeOpOverload)
             and get_edge_overload_packet(arg.target)
-            == exir_ops.edge.quantized_decomposed.dequantize_per_tensor
+            in (
+                exir_ops.edge.quantized_decomposed.dequantize_per_tensor,
+                exir_ops.edge.cadence.dequantize_per_tensor,
+            )
         ]
         multiplier_nodes = [
             arg

backends/cadence/aot/remove_ops.py

@@ -569,6 +569,8 @@ class Subgraph:
         exir_ops.edge.aten.hardtanh.default,
         exir_ops.edge.quantized_decomposed.quantize_per_tensor.default,
         exir_ops.edge.quantized_decomposed.dequantize_per_tensor.default,
+        exir_ops.edge.cadence.quantize_per_tensor.default,
+        exir_ops.edge.cadence.dequantize_per_tensor.default,
     }
 
     # must be initialized in the constructor

backends/cadence/aot/reorder_ops.py

@@ -118,6 +118,8 @@ def get_descendent_quant_ops(self, node: torch.fx.Node) -> List[torch.fx.Node]:
             if user_target in {
                 torch.ops.quantized_decomposed.quantize_per_tensor,
                 exir_ops.edge.quantized_decomposed.quantize_per_tensor,
+                torch.ops.cadence.quantize_per_tensor,
+                exir_ops.edge.cadence.quantize_per_tensor,
             }:
                 descendent_quant_ops.append(user)
             # If the successor is a trivially quantizable op, consider its users
@@ -300,6 +302,8 @@ def advance_quantize_op(self, graph_module: torch.fx.GraphModule):
             if get_overload_packet(node.target) not in (
                 exir_ops.edge.quantized_decomposed.quantize_per_tensor,
                 torch.ops.quantized_decomposed.quantize_per_tensor,
+                exir_ops.edge.cadence.quantize_per_tensor,
+                torch.ops.cadence.quantize_per_tensor,
             ):
                 continue
 
@@ -413,6 +417,7 @@ def postponing_feasible(self, dequant_node: torch.fx.Node):
             in {
                 exir_ops.edge.quantized_decomposed.quantize_per_tensor,
                 exir_ops.edge.quantized_decomposed.quantize_per_channel,
+                exir_ops.edge.cadence.quantize_per_tensor,
             }
             for x in users
         )
@@ -422,6 +427,7 @@ def postpone_dequantize_op(self, graph_module: torch.fx.GraphModule) -> bool:
         packet_to_overload_map = {
             exir_ops.edge.quantized_decomposed.dequantize_per_tensor: "default",
             exir_ops.edge.quantized_decomposed.dequantize_per_channel: "default",
+            exir_ops.edge.cadence.dequantize_per_tensor: "default",
         }
         graph = graph_module.graph
         modified = False
@@ -500,6 +506,7 @@ class SinkOpsCloserToUsePass(ExportPass):
         exir_ops.edge.aten.dequantize,
         exir_ops.edge.quantized_decomposed.dequantize_per_tensor,
         exir_ops.edge.quantized_decomposed.dequantize_per_channel,
+        exir_ops.edge.cadence.dequantize_per_tensor,
     }
 
     def sink_ops_closer_to_use(self, graph_module: torch.fx.GraphModule):
@@ -558,6 +565,7 @@ class HoistOpsCloserToDefPass(ExportPass):
 
     hoistable_ops: Set[EdgeOpOverload] = {
         exir_ops.edge.quantized_decomposed.quantize_per_tensor,
+        exir_ops.edge.cadence.quantize_per_tensor,
         exir_ops.edge.aten.slice_copy,
         exir_ops.edge.aten.select_copy,
     }

backends/cadence/aot/replace_ops.py

@@ -162,11 +162,12 @@ def call_operator(
         kwargs: Dict[str, Argument],
         meta: NodeMetadata,
     ) -> ProxyValue:
-        if op not in {exir_ops.edge.quantized_decomposed.quantize_per_tensor.default}:
+        ns = exir_ops.edge if isinstance(op, EdgeOpOverload) else torch.ops
+        if op != ns.quantized_decomposed.quantize_per_tensor.default:
             return super().call_operator(op, args, kwargs, meta)
 
         return super().call_operator(
-            exir_ops.edge.cadence.quantize_per_tensor.default,
+            ns.cadence.quantize_per_tensor.default,
             args,
             kwargs,
             meta,
@@ -188,11 +189,12 @@ def call_operator(
         kwargs: Dict[str, Argument],
         meta: NodeMetadata,
     ) -> ProxyValue:
-        if op not in {exir_ops.edge.quantized_decomposed.dequantize_per_tensor.default}:
+        ns = exir_ops.edge if isinstance(op, EdgeOpOverload) else torch.ops
+        if op != ns.quantized_decomposed.dequantize_per_tensor.default:
             return super().call_operator(op, args, kwargs, meta)
 
         return super().call_operator(
-            exir_ops.edge.cadence.dequantize_per_tensor.default,
+            ns.cadence.dequantize_per_tensor.default,
             args,
             kwargs,
             meta,