Arm backend: Add dtype check for aten.where in operator support check (#14506)

- Previously, aten.where with non-quantized FP inputs can pass the the
operator support check in INT profile, get partitioned, and then be
removed from the partition due to FP inputs.

- This will introduce dependency cycles, an invalid re-entry pattern
`partition -> outside -> partition`, to the graph.

- Workaround: when aten.where(cond, x, y) has FP x and y in INT profile,
only partition if both come from dequantize ops (DQ_OPS). Note this may
over-reject cases like `dq -> op1 -> aten.where -> q` that could be
partitioned.

- Don't partition aten.where with unsupported input dtype in FP profle.


Signed-off-by: Yufeng Shi <[email protected]>

Author: YufengShi-dudu

backends/arm/operator_support/__init__.py

@@ -19,4 +19,5 @@
     slice_copy_support,
     to_dim_order_copy_support,
     tosa_supported_operators,
+    where_support,
 )

backends/arm/operator_support/tosa_profile_supported_op_lists.py

@@ -104,7 +104,6 @@
     exir_ops.edge.aten.squeeze_copy.dims,
     exir_ops.edge.aten.pow.Tensor_Scalar,
     exir_ops.edge.aten.pow.Tensor_Tensor,
-    exir_ops.edge.aten.where.self,
     operator.getitem,
     exir_ops.edge.quantized_decomposed.quantize_per_tensor.default,
     exir_ops.edge.quantized_decomposed.quantize_per_channel.default,
@@ -220,7 +219,6 @@
     exir_ops.edge.aten.squeeze_copy.dims,
     exir_ops.edge.aten.pow.Tensor_Scalar,
     exir_ops.edge.aten.pow.Tensor_Tensor,
-    exir_ops.edge.aten.where.self,
     operator.getitem,
     exir_ops.edge.aten.constant_pad_nd.default,
     exir_ops.edge.aten.amax.default,

backends/arm/operator_support/where_support.py

@@ -0,0 +1,77 @@
+# Copyright 2025 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.
+
+
+import torch
+
+import torch.fx as fx
+from executorch.backends.arm.constants import DQ_OPS
+from executorch.backends.arm.operator_support.tosa_supported_operators import (
+    register_tosa_support_check,
+    SupportedTOSAOperatorCheck,
+)
+from executorch.backends.arm.tosa import TosaSpecification
+from executorch.exir.dialects._ops import ops as exir_ops
+
+
+@register_tosa_support_check
+class WhereSupported(SupportedTOSAOperatorCheck):
+    targets = [exir_ops.edge.aten.where.self]
+
+    tosa_specs = [
+        TosaSpecification.create_from_string("TOSA-1.0+INT"),
+        TosaSpecification.create_from_string("TOSA-1.0+FP"),
+    ]
+
+    def is_node_tosa_supported(
+        self, node: fx.Node, tosa_spec: TosaSpecification
+    ) -> bool:  # type: ignore[override, misc]
+
+        if len(node.all_input_nodes) != 3:
+            self.reporter.report_reject(
+                node,
+                (
+                    "Expected exactly three input nodes, "
+                    f"got {len(node.all_input_nodes)} for {node.target}."
+                ),
+            )
+            return False
+
+        condition, x, y = node.all_input_nodes
+        if condition.meta["val"].dtype != torch.bool:
+            self.reporter.report_reject(
+                node,
+                f"Type of condition in {node.target} is not torch.bool",
+            )
+            return False
+
+        x_dtype, y_dtype = x.meta["val"].dtype, y.meta["val"].dtype
+        if tosa_spec.support_float():
+            if x_dtype in (torch.bool, torch.float16, torch.float32) and y_dtype in (
+                torch.bool,
+                torch.float16,
+                torch.float32,
+            ):
+                return True
+
+        if tosa_spec.support_integer():
+            if (
+                x_dtype in (torch.bool, torch.int8, torch.int16, torch.int32)
+                or (x_dtype == torch.float32 and x.target in DQ_OPS)
+            ) and (
+                y_dtype in (torch.bool, torch.int8, torch.int16, torch.int32)
+                or (y_dtype == torch.float32 and y.target in DQ_OPS)
+            ):
+                return True
+
+        self.reporter.report_reject(
+            node,
+            (
+                f"Tensor x dtype {x_dtype} and/or tensor y dtype {y_dtype} is not supported in {node.target} "
+                f"for tosa specification {tosa_spec}"
+            ),
+        )
+
+        return False

backends/arm/test/models/stable_diffusion/test_CLIPTextModelWithProjection.py

@@ -6,7 +6,6 @@
 
 import unittest
 
-import pytest
 import torch
 from executorch.backends.arm._passes import (
     ConvertInt64ConstOpsToInt32Pass,
@@ -28,16 +27,25 @@ class TestCLIPTextModelWithProjection(unittest.TestCase):
     CLIPTextModelWithProjection is one of the text_encoder used by Stable Diffusion 3.5 Medium
     """
 
-    # Adjust nbr below as we increase op support. Note: most of the delegates
-    # calls are directly consecutive to each other in the .pte. The reason
-    # for that is some assert ops are removed by passes in the
-    # .to_executorch step, i.e. after Arm partitioner.
-    ops_after_partitioner = {
+    # Adjust nbr below as we increase op support.
+    ops_after_partitioner_FP = {
         "executorch_exir_dialects_edge__ops_aten_argmax_default": 1,
         "executorch_exir_dialects_edge__ops_dim_order_ops__to_dim_order_copy_default": 2,
         "torch.ops.higher_order.executorch_call_delegate": 2,
     }
 
+    ops_after_partitioner_INT = {
+        "executorch_exir_dialects_edge__ops_aten_argmax_default": 1,
+        "executorch_exir_dialects_edge__ops_aten_full_default": 1,
+        "executorch_exir_dialects_edge__ops_aten_index_select_default": 1,
+        "executorch_exir_dialects_edge__ops_aten_slice_copy_Tensor": 1,
+        "executorch_exir_dialects_edge__ops_aten_view_copy_default": 1,
+        "executorch_exir_dialects_edge__ops_aten_where_self": 1,
+        "executorch_exir_dialects_edge__ops_dim_order_ops__to_dim_order_copy_default": 2,
+        "torch.ops.aten.scalar_tensor.default": 1,
+        "torch.ops.higher_order.executorch_call_delegate": 2,
+    }
+
     def _prepare_inputs(
         self,
         batch_size=12,
@@ -78,14 +86,13 @@ def test_CLIPTextModelWithProjection_tosa_FP(self):
                 .export()
                 .to_edge_transform_and_lower()
                 .dump_operator_distribution()
-                .check_count(self.ops_after_partitioner)
+                .check_count(self.ops_after_partitioner_FP)
                 .to_executorch()
                 .run_method_and_compare_outputs(
                     inputs=text_encoder_model_inputs,
                 )
             )
 
-    @pytest.mark.xfail(raises=AssertionError, reason="Output difference.")
     def test_CLIPTextModelWithProjection_tosa_INT(self):
         text_encoder_model, text_encoder_model_inputs = self.prepare_model_and_inputs()
         with torch.no_grad():
@@ -99,8 +106,10 @@ def test_CLIPTextModelWithProjection_tosa_INT(self):
                 .export()
                 .to_edge_transform_and_lower()
                 .dump_operator_distribution()
+                .check_count(self.ops_after_partitioner_INT)
                 .to_executorch()
                 .run_method_and_compare_outputs(
                     inputs=text_encoder_model_inputs,
+                    atol=0.8,
                 )
             )

backends/arm/test/ops/test_where.py

@@ -139,8 +139,11 @@ def scalar_condition(input: torch.Tensor):
 
 test_modules_FP = {
     **test_modules_common,
-    "float32_tensor_cond_tuple_dtype": lambda: float32_tensor_cond_tuple_dtype,
     "float32_tensor_cond_tuple_dtype_bool": lambda: float32_tensor_cond_tuple_dtype_bool,
+}
+
+test_modules_FP_unsupported_dtype = {
+    "float32_tensor_cond_tuple_dtype": lambda: float32_tensor_cond_tuple_dtype,
     "int32_scalar_cond": lambda: int32_scalar_cond,
 }
 
@@ -162,6 +165,17 @@ def test_where_self_tosa_FP(test_module):
     pipeline.run()
 
 
+@common.parametrize("test_module", test_modules_FP_unsupported_dtype)
+def test_where_self_tosa_FP_unsupported_dtype(test_module):
+    pipeline = OpNotSupportedPipeline[input_t](
+        test_module(),
+        test_module().get_inputs(),
+        {exir_op: 1},
+        n_expected_delegates=1,  # condition can be delegated
+    )
+    pipeline.run()
+
+
 @common.parametrize("test_module", test_modules_INT)
 def test_where_self_tosa_INT(test_module):
     pipeline = TosaPipelineINT[input_t](