Arm backend: Add support for sqrt (#9928)

The sqrt operation is implemented via the pow operator, sqrt(x) = pow(x,
0.5).

Signed-off-by: Fang-Ching <[email protected]>

Author: fumchin

backends/arm/_passes/__init__.py

@@ -27,6 +27,7 @@
 from .decompose_select import DecomposeSelectPass  # noqa
 from .decompose_softmax_pass import DecomposeSoftmaxPass  # noqa
 from .decompose_softmax_unstable_pass import DecomposeSoftmaxUnstablePass  # noqa
+from .decompose_sqrt_pass import DecomposeSqrtPass  # noqa
 from .decompose_var_pass import DecomposeVarPass  # noqa
 from .fold_qdq_with_annotated_qparams_pass import (  # noqa
     FoldAndAnnotateQParamsPass,

backends/arm/_passes/arm_pass_manager.py

@@ -32,6 +32,7 @@
     DecomposeSelectPass,
     DecomposeSoftmaxPass,
     DecomposeSoftmaxUnstablePass,
+    DecomposeSqrtPass,
     DecomposeVarPass,
     FoldAndAnnotateQParamsPass,
     FuseBatchnorm2DPass,
@@ -115,6 +116,7 @@ def _tosa_080_BI_pipeline(self, exported_program: ExportedProgram) -> GraphModul
         return self._transform(exported_program.graph_module)
 
     def _tosa_080_MI_pipeline(self, exported_program: ExportedProgram) -> GraphModule:
+        self.add_pass(DecomposeSqrtPass())
         self.add_pass(ReplaceScalarWithTensorArgPassTOSAMI())
         self.add_pass(FuseQuantizedActivationPass())
         self.add_pass(RemoveGetItemPass())
@@ -181,6 +183,7 @@ def transform_for_annotation_pipeline(self, graph_module: GraphModule):
         self.add_pass(DecomposeMeanDimPass())
         self.add_pass(DecomposeDivPass())
         self.add_pass(DecomposeLeakyReLUPass())
+        self.add_pass(DecomposeSqrtPass())
 
         if isinstance(self.tosa_spec, Tosa_0_80) and self.tosa_spec.is_U55_subset:
             # Numerically stable softmax uses amax which is not supported on Ethos-U55

backends/arm/_passes/decompose_sqrt_pass.py

@@ -0,0 +1,39 @@
+# 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.
+
+# pyre-unsafe
+import torch
+from executorch.exir.dialects._ops import ops as exir_ops
+from executorch.exir.pass_base import ExportPass
+
+edge_sqrt_ops = (exir_ops.edge.aten.sqrt.default,)
+aten_sqrt_ops = (
+    torch.ops.aten.sqrt.default,
+    torch.ops.aten.sqrt_.default,
+)
+
+
+def get_sqrt_decomposition(op) -> tuple:
+    # TODO : "MLETORCH-863 : Replace current sqrt -> pow.Tensor_Scalar workaround with pow.Tensor_Tensor"
+    if op in edge_sqrt_ops:
+        return exir_ops.edge.aten.pow.Tensor_Scalar
+    if op in aten_sqrt_ops:
+        return torch.ops.aten.pow.Tensor_Scalar
+    raise RuntimeError(f"Can't get sqrt decomposition for op {op}")
+
+
+class DecomposeSqrtPass(ExportPass):
+
+    def call_operator(self, op, args, kwargs, meta):
+        """
+        Decomposes `sqrt(x)` into `pow(x, 0.5)` for backend support.
+        """
+
+        if op not in (edge_sqrt_ops + aten_sqrt_ops):
+            return super().call_operator(op, args, kwargs, meta)
+
+        pow_op = get_sqrt_decomposition(op)
+
+        return super().call_operator(pow_op, (args[0], 0.5), {}, meta)

backends/arm/operator_support/tosa_supported_operators.py

@@ -196,6 +196,7 @@ def is_node_supported(
             exir_ops.edge.aten.reciprocal.default,
             exir_ops.edge.aten.relu.default,
             exir_ops.edge.aten.leaky_relu.default,
+            exir_ops.edge.aten.sqrt.default,
             exir_ops.edge.aten.rsqrt.default,
             exir_ops.edge.aten._softmax.default,
             exir_ops.edge.aten.select_copy.int,
@@ -258,6 +259,7 @@ def is_node_supported(
                 exir_ops.edge.aten.var.correction,
                 exir_ops.edge.aten.var.dim,
                 exir_ops.edge.aten.add.Scalar,
+                exir_ops.edge.aten.sqrt.default,
                 exir_ops.edge.aten.sub.Scalar,
                 exir_ops.edge.aten.mul.Scalar,
                 exir_ops.edge.aten.div.Scalar,

backends/arm/test/ops/test_sqrt.py

@@ -0,0 +1,78 @@
+# 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.
+
+
+from typing import Dict, Tuple
+
+import torch
+from executorch.backends.arm.test import common
+from executorch.backends.arm.test.tester.test_pipeline import (
+    EthosU55PipelineBI,
+    EthosU85PipelineBI,
+    TosaPipelineBI,
+    TosaPipelineMI,
+)
+
+
+class Sqrt(torch.nn.Module):
+    input_t = Tuple[torch.Tensor]
+    aten_op_MI = "torch.ops.aten.sqrt.default"
+    exir_op_MI = "executorch_exir_dialects_edge__ops_aten_pow_Tensor_Tensor"
+
+    aten_op_BI = "torch.ops.aten.pow.Tensor_Scalar"
+    exir_op_BI = "executorch_exir_dialects_edge__ops_aten_pow_Tensor_Scalar"
+
+    def __init__(self):
+        super().__init__()
+
+    def forward(self, x):
+        return torch.sqrt(x)
+
+    test_data: Dict[str, input_t] = {
+        "sqrt_tensor_rank1_ones": (torch.ones(10),),
+        "sqrt_tensor_rank2_random": (torch.rand(5, 10),),
+        "sqrt_tensor_rank3_ones": (torch.ones(2, 3, 4),),
+        "sqrt_tensor_rank4_random": (torch.rand(1, 3, 8, 8),),
+        "sqrt_tensor_rank4_multibatch": (torch.rand(2, 3, 4, 4),),
+    }
+
+
+fvp_xfails = {
+    "sqrt_tensor_rank4_multibatch": "MLETORCH-517 : Multiple batches not supported",
+}
+
+
+@common.parametrize("test_data", Sqrt.test_data)
+def test_sqrt_tosa_MI(test_data: Sqrt.input_t):
+    pipeline = TosaPipelineMI[Sqrt.input_t](
+        Sqrt(), test_data, Sqrt.aten_op_MI, Sqrt.exir_op_MI
+    )
+    pipeline.run()
+
+
+@common.parametrize("test_data", Sqrt.test_data)
+def test_sqrt_tosa_BI(test_data: Sqrt.input_t):
+    pipeline = TosaPipelineBI[Sqrt.input_t](
+        Sqrt(), test_data, Sqrt.aten_op_BI, Sqrt.exir_op_BI
+    )
+    pipeline.run()
+
+
+@common.parametrize("test_data", Sqrt.test_data, fvp_xfails)
+@common.XfailIfNoCorstone300
+def test_sqrt_u55_BI(test_data: Sqrt.input_t):
+    pipeline = EthosU55PipelineBI[Sqrt.input_t](
+        Sqrt(), test_data, Sqrt.aten_op_BI, Sqrt.exir_op_BI, run_on_fvp=True
+    )
+    pipeline.run()
+
+
+@common.parametrize("test_data", Sqrt.test_data, fvp_xfails)
+@common.XfailIfNoCorstone320
+def test_sqrt_u85_BI(test_data: Sqrt.input_t):
+    pipeline = EthosU85PipelineBI[Sqrt.input_t](
+        Sqrt(), test_data, Sqrt.aten_op_BI, Sqrt.exir_op_BI, run_on_fvp=True
+    )
+    pipeline.run()