Arm backend: Refactor tosa.Resize node-visitor

backends/arm/_passes/arm_pass_utils.py

@@ -14,6 +14,7 @@
 import torch.fx
 from executorch.backends.arm.common.debug import get_node_debug_info
 from executorch.backends.arm.common.type import ensure_type
+from executorch.backends.arm.tosa.mapping import TosaSpecialDtype
 from executorch.exir import ExportedProgram
 from executorch.exir.dialects._ops import ops as exir_ops
 from executorch.exir.dialects.edge._ops import EdgeOpOverload
@@ -172,6 +173,30 @@ def create_node(
     return node
 
 
+def create_shape_node(
+    graph: torch.fx.Graph,
+    op_target: EdgeOpOverload,
+    args: tuple = (),
+    kwargs: Optional[dict] = None,
+    from_node: Optional[torch.fx.Node] = None,
+):
+    """Adds a shape node to 'graph'.
+
+    graph.inserting_before/after() should be used before the call to decide
+    where to insert the node.
+
+    """
+    node = create_node(
+        graph=graph,
+        op_target=op_target,
+        args=args,
+        kwargs=kwargs,
+        from_node=from_node,
+    )
+    node.meta[TosaSpecialDtype.meta_key()] = TosaSpecialDtype.SHAPE
+    return node
+
+
 def insert_q_dq_pair(
     graph: torch.fx.Graph,
     anchor: torch.fx.Node,

backends/arm/_passes/rewrite_upsample.py

@@ -1,24 +1,35 @@
-# Copyright 2025 Arm Limited and/or its affiliates.
+# Copyright 2025-2026 Arm Limited and/or its affiliates.
 #
 # This source code is licensed under the BSD-style license found in the
 # LICENSE file in the root directory of this source tree.
 
 from typing import Set, Type
 
+import sympy  # type: ignore
+
 import torch
 from executorch.backends.arm._passes import ArmPass
 from executorch.backends.arm._passes.arm_pass_utils import (
     create_node,
+    create_shape_node,
     get_first_fake_tensor,
 )
 from executorch.backends.arm.tosa.mapping import TosaSpecialDtype
-from executorch.backends.arm.tosa.utils import get_resize_parameters
 from executorch.exir.dialects._ops import ops as exir_ops
 from executorch.exir.pass_base import ExportPass, PassResult
 
 
 class RewriteUpsamplePass(ArmPass):
-    """Rewrite upsample2d nodes to TOSA.RESIZE nodes."""
+    """Rewrite upsample2d nodes to TOSA.RESIZE nodes with appropriate
+    parameters.
+
+    For constant parameters, CONST_SHAPE nodes are inserted for the scale,
+    offset, and border values. For symbolic parameters, the parameters are
+    directly passed to the TOSA.RESIZE node, and we rely on subsequent passes to
+    handle them correctly once symbolic shapes are delegated by the TOSA
+    backend.
+
+    """
 
     targeted_ops = (
         exir_ops.edge.aten.upsample_nearest2d.vec,
@@ -27,6 +38,89 @@ class RewriteUpsamplePass(ArmPass):
 
     _passes_required_after: Set[Type[ExportPass]] = set()
 
+    @staticmethod
+    def get_resize_parameters_1d(
+        input_size: int | torch.SymInt,
+        output_size: int | torch.SymInt,
+        align_corners: bool,
+    ):
+        """Compute resize coefficients for a single spatial dimension.
+
+        Args:
+            input_size (int | torch.SymInt): Input size for the axis, possibly
+                symbolic.
+            output_size (int | torch.SymInt): Output size for the axis, possibly
+                symbolic.
+            align_corners (bool): Whether the resize should align the corner
+                pixels.
+
+        Returns:
+            tuple[int, int, int, int]: Numerator, denominator, offset, and border
+                terms encoded as integers.
+
+        Raises:
+            RuntimeError: If symbolic shapes are used with ``align_corners`` or if
+                the computed ratio or border is not constant.
+
+        """
+        # We don't support align_corners for symbolic shapes, because handling the edge case where size == 1 is tricky.
+        if align_corners:
+            if (not isinstance(input_size, int)) or (not isinstance(output_size, int)):
+                raise RuntimeError(
+                    "We do not support align_corners=True for symbolic shapes."
+                )
+
+        # SymInt seems to not actually work for symbolic expressions, so use the underlying sympy objects instead
+        input_size = (
+            input_size.node._expr
+            if isinstance(input_size, torch.SymInt)
+            else input_size
+        )
+        output_size = (
+            output_size.node._expr
+            if isinstance(output_size, torch.SymInt)
+            else output_size
+        )
+        if align_corners and input_size > 1 and output_size > 1:
+            scale_n = output_size - 1
+        else:
+            scale_n = output_size
+        if align_corners and input_size > 1 and output_size > 1:
+            scale_d = input_size - 1
+        else:
+            scale_d = input_size
+        ratio = scale_n / scale_d
+        if not sympy.sympify(ratio).is_constant():
+            raise RuntimeError(
+                "Resize requires a constant ratio: " + str(ratio) + " is not constant!"
+            )
+        gcd = sympy.gcd(scale_n, scale_d)
+        scale_n = 2 * scale_n // gcd
+        scale_d = 2 * scale_d // gcd
+        # These should always be whole integers, based on the above calculations
+        scale_n = int(scale_n.evalf())
+        scale_d = int(scale_d.evalf())
+
+        if align_corners:
+            offset = 0
+        else:
+            # Half pixel centers so input and output sampling positions are offset by 1/2 pixel.
+            offset = scale_d // 2 - scale_n // 2
+
+        # Calculate border to maintain the correct the output size.
+        # Note that this should always result in a constant value, as the ratio is constant.
+        border = scale_d * (output_size - 1) - scale_n * (input_size - 1) + offset
+
+        if not sympy.sympify(border).is_constant():
+            raise RuntimeError(
+                "Resize requires a constant border: "
+                + str(border)
+                + " is not constant!"
+            )
+
+        border = int(sympy.sympify(border).evalf())
+        return scale_n, scale_d, offset, border
+
     def call(self, graph_module):
         modified = False
         for node in graph_module.graph.nodes:
@@ -39,14 +133,65 @@ def call(self, graph_module):
                 resize_mode = "bilinear"
             else:
                 x, output_size, scale_factors = node.args
+                # As per https://docs.pytorch.org/docs/stable/generated/torch.nn.Upsample.html
+                # align_corners is not valid for nearest mode. Default to False.
                 align_corners = False
                 resize_mode = "nearest"
 
+            input_size_yx = node.args[0].meta["val"].shape[2:]
+            output_size_yx = node.meta["val"].shape[2:]
+
+            scale_y_n, scale_y_d, offset_y, border_y = (
+                RewriteUpsamplePass.get_resize_parameters_1d(
+                    input_size_yx[0], output_size_yx[0], align_corners
+                )
+            )
+            scale_x_n, scale_x_d, offset_x, border_x = (
+                RewriteUpsamplePass.get_resize_parameters_1d(
+                    input_size_yx[1], output_size_yx[1], align_corners
+                )
+            )
+
+            scales = [
+                scale_y_n,
+                scale_y_d,
+                scale_x_n,
+                scale_x_d,
+            ]
             with graph_module.graph.inserting_before(node):
+                if all(isinstance(s, int) for s in scales):
+                    scale = create_shape_node(
+                        graph_module.graph,
+                        op_target=exir_ops.backend.tosa.CONST_SHAPE.default,
+                        args=(scales,),
+                        kwargs={},
+                        from_node=node,
+                    )
+                else:
+                    scale = scales
+                offset = [offset_y, offset_x]
+                if all(isinstance(o, int) for o in offset):
+                    offset = create_shape_node(
+                        graph_module.graph,
+                        op_target=exir_ops.backend.tosa.CONST_SHAPE.default,
+                        args=(offset,),
+                        kwargs={},
+                        from_node=node,
+                    )
+                border = [border_y, border_x]
+                if all(isinstance(b, int) for b in border):
+                    border = create_shape_node(
+                        graph_module.graph,
+                        op_target=exir_ops.backend.tosa.CONST_SHAPE.default,
+                        args=(border,),
+                        kwargs={},
+                        from_node=node,
+                    )
+
                 tosa_resize_node = create_node(
                     graph_module.graph,
                     op_target=exir_ops.backend.tosa.RESIZE.default,
-                    args=(x, output_size, align_corners, scale_factors),
+                    args=(x, scale, offset, border),
                     kwargs={"resize_mode": resize_mode},
                     from_node=node,
                     inherit_qparams=True,
@@ -57,18 +202,8 @@ def call(self, graph_module):
             if (
                 input_dtype == torch.int8 or input_dtype == torch.int16
             ) and resize_mode == "bilinear":
-                input_size = get_first_fake_tensor(x).shape
-                input_size_xy = input_size[2:]
-                output_size = get_first_fake_tensor(node).shape
-                output_size_xy = output_size[2:]
-                scale_n_yx, _, _, _ = get_resize_parameters(
-                    input_size_xy=input_size_xy,
-                    output_size_xy=output_size_xy,
-                    resize_mode=1,
-                    align_corners=align_corners,
-                )
                 output_dtype = get_first_fake_tensor(node).dtype
-                output_scale = float(1 / (scale_n_yx[0] * scale_n_yx[1]))
+                output_scale = float(1 / (scale_y_n * scale_x_n))
                 with graph_module.graph.inserting_after(tosa_resize_node):
                     rescale_node = create_node(
                         graph_module.graph,

backends/arm/_passes/to_tosa_memory_format_pass.py

@@ -436,6 +436,9 @@ def _propagate_dim_order_to_shape_args(self, node: torch.fx.Node) -> None:
                     raise RuntimeError(
                         f"Conflicting dim orders {arg.meta['tosa_dim_order']} and {dim_order} for shape node {arg.name}"
                     )
+                if node.target == exir_ops.backend.tosa.RESIZE.default:
+                    # RESIZE's shape input is expected to be in HW order, so we need to override the dim order to be the identity for it regardless of the user node's dim order.
+                    dim_order = tuple(range(len(arg.meta["val"])))
                 arg.meta["tosa_dim_order"] = dim_order
                 self._propagate_dim_order_to_shape_args(arg)
 

backends/arm/operators/op_tosa_resize.py

@@ -15,11 +15,8 @@
 )
 from executorch.backends.arm.operators.operator_validation_utils import (
     validate_num_inputs,
-    validate_same_dtype,
-    validate_valid_dtype,
 )
 from executorch.backends.arm.tosa.mapping import TosaArg
-from executorch.backends.arm.tosa.utils import get_resize_parameters
 
 
 @register_node_visitor
@@ -36,81 +33,12 @@ def define_node(
         inputs: List[TosaArg],
         output: TosaArg,
     ) -> None:
-        validate_num_inputs(self.target, inputs, [3, 4])
-        supported_input_dtypes = [
-            ts.DType.INT8,
-            ts.DType.FP16,
-            ts.DType.FP32,
-            ts.DType.BF16,
-        ]
-        if self.tosa_spec.support_extension("int16"):
-            supported_input_dtypes.append(ts.DType.INT16)
-        if self.tosa_spec.support_extension("bf16"):
-            supported_input_dtypes.append(ts.DType.BF16)
-        validate_valid_dtype(
-            self.target,
-            [inputs[0]],
-            supported_input_dtypes,
-            self.tosa_spec,
-        )
-        supported_output_dtypes = [ts.DType.FP16, ts.DType.FP32, ts.DType.BF16]
+        x, scales, offset, border = inputs
+        validate_num_inputs(self.target, inputs, [4])
         if node.kwargs.get("resize_mode") == "bilinear":
             resize_mode = ts.ResizeMode.BILINEAR
-            align_corners = bool(node.args[2])
-            supported_output_dtypes.append(ts.DType.INT32)
-            if self.tosa_spec.support_extension("int16"):
-                supported_output_dtypes.append(ts.DType.INT48)
         else:
             resize_mode = ts.ResizeMode.NEAREST
-            align_corners = False
-            validate_same_dtype(self.target, [inputs[0], output], ts)
-            supported_output_dtypes.append(ts.DType.INT8)
-            if self.tosa_spec.support_extension("int16"):
-                supported_output_dtypes.append(ts.DType.INT16)
-        validate_valid_dtype(
-            self.target, [output], supported_output_dtypes, self.tosa_spec
-        )
-        # tosa_shape output is NHWC, take HW
-        input_size_yx = tuple([inputs[0].shape[dim] for dim in inputs[0].dim_order])[
-            1:3
-        ]
-        output_size_yx = tuple([output.shape[dim] for dim in output.dim_order])[1:3]
-
-        # Align corners shouldn't make a difference for nearest upsampling. We set to False so
-        # half pixel centers are used for resize parameter logic.
-        scale_n_yx, scale_d_yx, offset_yx, border_yx = get_resize_parameters(
-            input_size_yx, output_size_yx, resize_mode, align_corners=align_corners
-        )
-
-        def in_int16_range(x):
-            return torch.all(x >= -(2**15)) and torch.all(x <= 2**15 - 1)
-
-        if not in_int16_range(scale_n_yx):
-            raise ValueError("scale_n_yx is out of the int16 range")
-        if not in_int16_range(scale_d_yx):
-            raise ValueError("scale_d_yx is out of the int16 range")
-        if not in_int16_range(border_yx):
-            raise ValueError("border_yx is out of the int16 range")
-
-        scale_n_vals = [int(v) for v in scale_n_yx.tolist()]
-        scale_d_vals = [int(v) for v in scale_d_yx.tolist()]
-        scales = [
-            scale_n_vals[0],
-            scale_d_vals[0],
-            scale_n_vals[1],
-            scale_d_vals[1],
-        ]
-        scales_tensor = tosa_graph.addConst(
-            [len(scales)], ts.DType.SHAPE, scales, output.name + "_scales"
-        )
-        offset = [int(v) for v in offset_yx.tolist()]
-        offset_tensor = tosa_graph.addConst(
-            [len(offset)], ts.DType.SHAPE, offset, output.name + "_offset"
-        )
-        border = [int(v) for v in border_yx.tolist()]
-        border_tensor = tosa_graph.addConst(
-            [len(border)], ts.DType.SHAPE, border, output.name + "_border"
-        )
         attr = ts.TosaSerializerAttribute()
         attr.ResizeAttribute(resize_mode)
 
@@ -119,10 +47,10 @@ def in_int16_range(x):
             tosa_graph,
             ts.Op.RESIZE,
             [
-                inputs[0].name,
-                scales_tensor.name,
-                offset_tensor.name,
-                border_tensor.name,
+                x.name,
+                scales.name,
+                offset.name,
+                border.name,
             ],
             [output.name],
             attr,