Arm backend: Simplify fake RESIZE validation

Avoid revalidating RESIZE output shape against dimensions computed by
the same formula. Validate parameters once, compute the fake output
shape, and directly validate the computed output dimensions.

Signed-off-by: Per Held <per.held@arm.com>
Change-Id: I97bb91f9fc440c980782955692056196038d5de0

Author: perheld

backends/arm/test/misc/tosa_dialect/test_tosa_resize.py

@@ -72,6 +72,30 @@ def test_resize_rejects_scale_numerator_over_tosa_limit():
             )
 
 
+@pytest.mark.parametrize(
+    "offset,border",
+    (
+        ([1, 0], [-1, 0]),
+        ([0, 1], [0, -1]),
+    ),
+)
+def test_resize_rejects_non_positive_output_dimensions(offset, border):
+    with TosaLoweringContext(
+        TosaSpecification.create_from_string("TOSA-1.0+INT")
+    ), FakeTensorMode() as mode:
+        with pytest.raises(
+            TosaValueError,
+            match="RESIZE output dimensions must be positive",
+        ):
+            exir_ops.backend.tosa.RESIZE.default(
+                mode.from_tensor(torch.randint(0, 10, (1, 1, 1, 1), dtype=torch.int8)),
+                [1, 1, 1, 1],
+                offset,
+                border,
+                resize_mode="nearest",
+            )
+
+
 def test_resize_accepts_symbolic_scale_and_border_values():
     shape_env = ShapeEnv()
     scale_y_n = _make_symint(shape_env, "scale_y_n", hint=2, min=1, max=8)

backends/arm/tosa/dialect/ops/resize.py

@@ -10,6 +10,7 @@
 from executorch.backends.arm.tosa.dialect.ops_registration import register_fake_tosa_op
 from executorch.backends.arm.tosa.resize_utils import (
     calculate_tosa_resize_output_hw,
+    get_tosa_resize_output_hw_validation_error,
     get_tosa_resize_validation_error,
 )
 
@@ -92,7 +93,9 @@ def RESIZE(
     H, W = input_shape[1], input_shape[2]
     _validate_resize_parameters((H, W), None, scale, offset, border, tosa_spec)
     output_hw = calculate_tosa_resize_output_hw((H, W), scale, offset, border)
-    _validate_resize_parameters((H, W), output_hw, scale, offset, border, tosa_spec)
+    validation_error = get_tosa_resize_output_hw_validation_error(output_hw)
+    if validation_error is not None:
+        raise TosaValueError(validation_error, op="RESIZE")
     if output_hw is None:
         scale_y_n, scale_y_d, scale_x_n, scale_x_d = scale
         offset_y, offset_x = offset

backends/arm/tosa/resize_utils.py

@@ -67,6 +67,25 @@ def _validate_dimensions(
     return None
 
 
+def get_tosa_resize_output_hw_validation_error(
+    output_hw: Sequence[int | torch.SymInt] | None,
+) -> str | None:
+    if output_hw is None:
+        return None
+
+    output_hw_ints = _as_concrete_ints(output_hw)
+    if output_hw_ints is None:
+        return None
+
+    invalid_dimension = next(
+        (dimension for dimension in output_hw_ints if dimension <= 0), None
+    )
+    if invalid_dimension is not None:
+        return f"RESIZE output dimensions must be positive; got {invalid_dimension}"
+
+    return _validate_dimensions((), output_hw)
+
+
 def _validate_scale(
     scale: Sequence[int | torch.SymInt],
     tosa_spec: TosaSpecification,