Arm backend: Move rescales from ADD & SUB visitors to pass (#15378)

Move the insertion of INT8/INT32 RESCALE ops from the SUB node visitor
to the pass InsertRescaleInt32Pass.

This is in practice a refactoring patch, but still the output TOSA files
becomes different enough to cause Ethos-U55/U85 tests to fail in
test_var.py and test_conv_relu_residual_add.py. However, the issue was
fixed in
https://gitlab.arm.com/artificial-intelligence/ethos-u/ethos-u-vela/-/commit/642f7517d3a6bd053032e1942822f6e38ccd546f
so we temporarily set the failing tests to xfail until the version of
Ethos-U Vela compiler depended on is bumped to one that includes the
fix.

### Test plan
test_insert_rescale_i32_pass.py has been modified to test the change.

Signed-off-by: Martin Lindström <[email protected]>
Co-authored-by: Oscar Andersson <[email protected]>

Author: martinlsm

backends/arm/_passes/insert_rescales_pass.py

@@ -76,13 +76,12 @@ def call(self, graph_module: GraphModule) -> PassResult:
 
 
 class InsertRescaleInt32Pass(ArmPass):
-    """
-    Numerous TOSA ops require inputs and outputs to be 32-bit integers in their
+    """Numerous TOSA ops require inputs and outputs to be 32-bit integers in their
     quantized implementations. This pass treats such operator nodes by
-    inserting rescale ops before and after them if needed. Note that extra logic
-    that handles the scales and zero points must be in place because the affected
-    TOSA have naive implementations that do not account for the quantization
-    parameters.
+    inserting rescale ops before and after them if needed. Note that extra
+    logic that handles the scales and zero points are in place here because the
+    affected TOSA ops have naive implementations that do not account for the
+    quantization parameters.
     """
 
     # SUM must be decomposed after this pass to prevent insertion of RESCALE
@@ -93,6 +92,7 @@ class InsertRescaleInt32Pass(ArmPass):
 
     included_targets = [
         exir_ops.edge.aten.abs.default,
+        exir_ops.edge.aten.add.Tensor,
         exir_ops.edge.aten.eq.Tensor,
         exir_ops.edge.aten.ge.Tensor,
         exir_ops.edge.aten.gt.Tensor,
@@ -101,6 +101,7 @@ class InsertRescaleInt32Pass(ArmPass):
         exir_ops.edge.aten.maximum.default,
         exir_ops.edge.aten.minimum.default,
         exir_ops.edge.aten.mul.Tensor,
+        exir_ops.edge.aten.sub.Tensor,
         exir_ops.edge.aten.sum.dim_IntList,
     ]
 
@@ -142,6 +143,34 @@ def _get_inputs_rescaled_qparams(
             qparams = {
                 i: self._int32_qargs(min_scale) for i in range(len(input_qparams))
             }
+        elif target in [
+            exir_ops.edge.aten.add.Tensor,
+            exir_ops.edge.aten.sub.Tensor,
+        ]:
+            if input_qparams[0].dtype != input_qparams[1].dtype:
+                raise ValueError(
+                    "Mismatch in dtype args: {input_qparams[0].dtype} != {input_qparams[1].dtype}"
+                )
+
+            # We are handling two INT8 or two INT16 numbers. For INT8, if the
+            # zero point is non-null, the result will be in the range [-255;
+            # 255], therefore we need 9 bits for the result. We have a 32-bit
+            # accumulator, so we can divide the scale by (1 << 20) which is
+            # equivalent to shifting the INT8 operands 20 bits to the left
+            # before rescaling them both to 2 * max(lhs, rhs).
+            #
+            # For INT16, similary logic can be applied, but we instead end up
+            # with a left shift of 12.
+            lhs_scale, rhs_scale = (
+                qp.get_scale_per_tensor() for qp in input_qparams.values()
+            )
+            max_scale_2x = 2 * max(lhs_scale, rhs_scale)
+
+            # Select shift based on input dtype.
+            shift_bits = 12 if input_qparams[0].dtype == torch.int16 else 20
+
+            scale = max_scale_2x / (1 << shift_bits)
+            qparams = {i: self._int32_qargs(scale) for i in range(len(input_qparams))}
         elif target in [
             exir_ops.edge.aten.mul.Tensor,
             exir_ops.edge.aten.sum.dim_IntList,
@@ -168,6 +197,8 @@ def _get_output_qparams(
             exir_ops.edge.aten.maximum.default,
             exir_ops.edge.aten.minimum.default,
             exir_ops.edge.aten.sum.dim_IntList,
+            exir_ops.edge.aten.add.Tensor,
+            exir_ops.edge.aten.sub.Tensor,
         ]:
             # The op has not altered the scale; the output scale is equal to
             # the operands' scales.

backends/arm/operators/op_add.py

@@ -6,8 +6,6 @@
 
 from typing import Any, List
 
-import executorch.backends.arm.tosa.quant_utils as tqutils
-import executorch.backends.arm.tosa.utils as tutils
 import tosa_serializer as ts
 
 from executorch.backends.arm.operators.node_visitor import (
@@ -19,22 +17,20 @@
     validate_same_dtype,
     validate_valid_dtype,
 )
-from executorch.backends.arm.tosa import TosaSpecification
 from executorch.backends.arm.tosa.mapping import TosaArg
+from executorch.backends.arm.tosa.specification import TosaSpecification
 from torch.fx import Node
 
 
 @register_node_visitor
-class AddVisitor_INT(NodeVisitor):
+class AddVisitor(NodeVisitor):
     target = "aten.add.Tensor"
 
     tosa_specs = [
         TosaSpecification.create_from_string("TOSA-1.0+INT"),
+        TosaSpecification.create_from_string("TOSA-1.0+FP"),
     ]
 
-    def __init__(self, *args):
-        super().__init__(*args)
-
     def define_node(
         self,
         node: Node,
@@ -44,113 +40,21 @@ def define_node(
     ) -> None:
         validate_num_inputs(self.target, inputs, 2)
         validate_same_dtype(self.target, [*inputs, output], ts)
-        valid_dtypes = []
-        if self.tosa_spec.support_integer():
-            valid_dtypes.extend([ts.DType.INT8, ts.DType.INT16, ts.DType.INT32])
-        if self.tosa_spec.support_float():
-            valid_dtypes.extend([ts.DType.INT32])
-
         validate_valid_dtype(
             self.target,
             [*inputs, output],
-            valid_dtypes,
+            [ts.DType.INT32, ts.DType.FP32],
             output.tosa_spec,
         )
-        scale_back = 1.0
-        if inputs[0].dtype == ts.DType.INT8:
-            rescaled_inputs, scale_back = tqutils.insert_rescale_ops_to_int32_maxscale(
-                tosa_graph, inputs, node, self.tosa_spec
-            )
-        elif inputs[0].dtype == ts.DType.INT16:
-            rescaled_inputs, scale_back = (
-                tqutils.insert_rescale_ops_int16_to_int32_maxscale(
-                    tosa_graph, inputs, node, self.tosa_spec
-                )
-            )
-        else:
-            # input[0].dtype == ts.DType.INT16 or ts.DType.INT32
-            # Non quantized input, natively support by TOSA.ADD
-            rescaled_inputs = inputs
-
-        if output.dtype in [ts.DType.INT8, ts.DType.INT16]:
-            broadcasted_shape = tutils.tosa_shape(output.shape, output.dim_order)
-            add_output = tosa_graph.addIntermediate(broadcasted_shape, ts.DType.INT32)
-        else:
-            # output.dtype == ts.DType.INT16 or ts.DType.INT32
-            add_output = output
 
-        input1, input2 = rescaled_inputs
         attr = ts.TosaSerializerAttribute()
         attr.AddAttribute()
-        # Do the INT32 Add
+
         self._serialize_operator(
             node,
             tosa_graph,
             ts.Op.ADD,
-            [input1.name, input2.name],
-            [add_output.name],
+            [inputs[0].name, inputs[1].name],
+            [output.name],
             attr,
         )
-
-        if output.dtype == ts.DType.INT8:
-            # Scale output back to 8 bit
-            # pyre-ignore
-            tqutils.insert_rescale_op_to_int8(
-                tosa_graph,
-                add_output,
-                scale_back,
-                node,
-                compute_rescale=False,
-                tosa_spec=self.tosa_spec,
-            )  # type: ignore[possibly-undefined]
-        elif output.dtype == ts.DType.INT16:
-            tqutils.insert_rescale_op_to_int16(
-                tosa_graph,
-                add_output,
-                scale_back,
-                node,
-                compute_rescale=False,
-                tosa_spec=self.tosa_spec,
-            )  # type: ignore[possibly-undefined]
-
-
-@register_node_visitor
-class AddVisitor_FP(AddVisitor_INT):
-    # inheriting 'target' from INT class
-
-    tosa_specs = [TosaSpecification.create_from_string("TOSA-1.0+FP")]
-
-    def __init__(self, *args):
-        super().__init__(*args)
-
-    def define_node(
-        self,
-        node: Node,
-        tosa_graph: Any,
-        inputs: List[TosaArg],
-        output: TosaArg,
-    ) -> None:
-        validate_num_inputs(self.target, inputs, 2)
-        validate_same_dtype(self.target, [*inputs, output], ts)
-
-        if inputs[0].dtype in [ts.DType.INT8, ts.DType.INT16, ts.DType.INT32]:
-            # Call the inherited define_node for handling integers
-            super().define_node(node, tosa_graph, inputs, output)
-        else:
-            # FP32 Add lowering
-            validate_valid_dtype(
-                self.target, [*inputs, output], ts.DType.FP32, output.tosa_spec
-            )
-
-            input1, input2 = inputs
-            attr = ts.TosaSerializerAttribute()
-            attr.AddAttribute()
-            # FP lowering
-            self._serialize_operator(
-                node,
-                tosa_graph,
-                ts.Op.ADD,
-                [input1.name, input2.name],
-                [output.name],
-                attr,
-            )

backends/arm/operators/op_sub.py

@@ -6,8 +6,6 @@
 
 from typing import Any, List
 
-import executorch.backends.arm.tosa.quant_utils as tqutils
-import executorch.backends.arm.tosa.utils as tutils
 import tosa_serializer as ts
 
 from executorch.backends.arm.operators.node_visitor import (
@@ -19,22 +17,20 @@
     validate_same_dtype,
     validate_valid_dtype,
 )
-from executorch.backends.arm.tosa import TosaSpecification
 from executorch.backends.arm.tosa.mapping import TosaArg
+from executorch.backends.arm.tosa.specification import TosaSpecification
 from torch.fx import Node
 
 
 @register_node_visitor
-class SubVisitor_INT(NodeVisitor):
+class SubVisitor(NodeVisitor):
     target = "aten.sub.Tensor"
 
     tosa_specs = [
         TosaSpecification.create_from_string("TOSA-1.0+INT"),
+        TosaSpecification.create_from_string("TOSA-1.0+FP"),
     ]
 
-    def __init__(self, *args):
-        super().__init__(*args)
-
     def define_node(
         self,
         node: Node,
@@ -47,106 +43,21 @@ def define_node(
         validate_valid_dtype(
             self.target,
             [*inputs, output],
-            [ts.DType.INT8, ts.DType.INT16, ts.DType.INT32],
+            [ts.DType.INT32, ts.DType.FP32],
             output.tosa_spec,
         )
 
-        scale_back = 1.0
-        if inputs[0].dtype == ts.DType.INT8:
-            rescaled_inputs, scale_back = tqutils.insert_rescale_ops_to_int32_maxscale(
-                tosa_graph, inputs, node, self.tosa_spec
-            )
-        elif inputs[0].dtype == ts.DType.INT16:
-            rescaled_inputs, scale_back = (
-                tqutils.insert_rescale_ops_int16_to_int32_maxscale(
-                    tosa_graph, inputs, node, self.tosa_spec
-                )
-            )
-        else:
-            # input[0].dtype == ts.DType.INT32
-            # Non quantized input, natively support by TOSA.SUB
-            rescaled_inputs = inputs
-
-        if output.dtype in [ts.DType.INT8, ts.DType.INT16]:
-            broadcasted_shape = tutils.tosa_shape(output.shape, output.dim_order)
-            sub_output = tosa_graph.addIntermediate(broadcasted_shape, ts.DType.INT32)
-        else:
-            # output.dtype == ts.DType.INT32
-            sub_output = output
-
-        # Do the INT32 Sub
         attr = ts.TosaSerializerAttribute()
         attr.SubAttribute()
+
         self._serialize_operator(
             node,
             tosa_graph,
             ts.Op.SUB,
             [
-                rescaled_inputs[0].name,
-                rescaled_inputs[1].name,
+                inputs[0].name,
+                inputs[1].name,
             ],
-            [sub_output.name],
+            [output.name],
             attr,
         )
-
-        if output.dtype == ts.DType.INT8:
-            # Scale output back to 8 bit
-            # pyre-ignore
-            tqutils.insert_rescale_op_to_int8(
-                tosa_graph,
-                sub_output,
-                scale_back,
-                node,
-                compute_rescale=False,
-                tosa_spec=self.tosa_spec,
-            )  # type: ignore[possibly-undefined]
-        elif output.dtype == ts.DType.INT16:
-            tqutils.insert_rescale_op_to_int16(
-                tosa_graph,
-                sub_output,
-                scale_back,
-                node,
-                compute_rescale=False,
-                tosa_spec=self.tosa_spec,
-            )  # type: ignore[possibly-undefined]
-
-
-@register_node_visitor
-class SubVisitor_FP(SubVisitor_INT):
-    # inheriting 'target' from INT class
-
-    tosa_specs = [TosaSpecification.create_from_string("TOSA-1.0+FP")]
-
-    def __init__(self, *args):
-        super().__init__(*args)
-
-    def define_node(
-        self,
-        node: Node,
-        tosa_graph: Any,
-        inputs: List[TosaArg],
-        output: TosaArg,
-    ) -> None:
-        validate_num_inputs(self.target, inputs, 2)
-        validate_same_dtype(self.target, [*inputs, output], ts)
-
-        if inputs[0].dtype in [ts.DType.INT8, ts.DType.INT32]:
-            # Call the inherited define_node for handling integers
-            super().define_node(node, tosa_graph, inputs, output)
-        else:
-            # FP32 Sub lowering
-            validate_valid_dtype(
-                self.target, [*inputs, output], ts.DType.FP32, output.tosa_spec
-            )
-
-            # MI lowering
-            attr = ts.TosaSerializerAttribute()
-            attr.SubAttribute()
-            self._serialize_operator(
-                node,
-                tosa_graph,
-                ts.Op.SUB,
-                [inputs[0].name, inputs[1].name],
-                [output.name],
-                attr,
-            )

backends/arm/test/misc/test_conv_relu_residual_add.py

@@ -76,6 +76,13 @@ def test_tosa_INT(per_channel_quantization):
     pipeline.run()
 
 
+# TODO: Xfail until the Ethos-U Vela compiler ships commit
+# 642f7517d3a6bd053032e1942822f6e38ccd546f. That patch fixes the bug that
+# causes this test to fail.
+@pytest.mark.xfail(
+    reason=("Blocked by Vela commit 642f7517d3a6bd053032e1942822f6e38ccd546f"),
+    strict=True,
+)
 @pytest.mark.slow
 @common.XfailIfNoCorstone300
 @common.parametrize("per_channel_quantization", quant_test_data)