Arm backend: Enable dynamic shapes in DecomposeMeanDimPass (#18774)

With the upcoming SymInt, enable dynamic shapes in DecomposeMeanDimPass.
Avg_pool2d operator is currently not supported.

Signed-off-by: Saoirse Stewart <saoirse.stewart@arm.com>
Co-authored-by: Oscar Andersson <oscar.andersson@arm.com>

Author: SaoirseARM

backends/arm/_passes/decompose_meandim_pass.py

@@ -35,6 +35,22 @@ def get_meandim_decomposition(op) -> tuple:
     raise RuntimeError(f"Can't get meandim decomposition for op {op}")
 
 
+def get_dynamic_meandim_decomposition(op) -> tuple:
+    if op in (exir_ops.edge.aten.mean.dim, exir_ops.edge.aten.mean.default):
+        return (
+            exir_ops.edge.aten.sum.dim_IntList,
+            exir_ops.edge.aten.mul.Tensor,
+            exir_ops.edge.aten.full.default,
+            exir_ops.edge.aten.reciprocal.default,
+            exir_ops.edge.aten.expand_copy.default,
+        )
+    if op in (torch.ops.aten.mean.dim, torch.ops.aten.mean.default):
+        raise NotImplementedError(
+            "Dynamic mean.dim decomposition is not supported for torch.aten.mean."
+        )
+    raise RuntimeError(f"Can't get meandim decomposition for op {op}")
+
+
 def get_avgpool(op):
     if op in (exir_ops.edge.aten.mean.dim, exir_ops.edge.aten.mean.default):
         return exir_ops.edge.aten.avg_pool2d.default
@@ -103,26 +119,39 @@ def __init__(self, graph_module, tosa_spec, *args, **kwargs):
             self._tosa_spec, WhyNoPartitionReporter()
         )
 
-    def call_operator(self, op, args, kwargs, meta):
+    def call_operator(self, op, args, kwargs, meta, updated=False):
         if op not in (
             exir_ops.edge.aten.mean.dim,
             torch.ops.aten.mean.dim,
             exir_ops.edge.aten.mean.default,
             torch.ops.aten.mean.default,
         ) or not self.allowed_to_transform(meta):
-            return super().call_operator(op, args, kwargs, meta)
+            return super().call_operator(op, args, kwargs, meta, updated)
 
         x = get_node_arg(args, 0)
         input_shape = list(x.data.shape)
         output_shape = list(meta["val"].shape)
+
         dims_to_reduce = get_node_arg(args, 1, range(len(input_shape)))
         if dims_to_reduce is None:
             dims_to_reduce = range(len(input_shape))
+
         dims_to_reduce = [dim % len(input_shape) for dim in dims_to_reduce]
-        dims_to_reduce = [dim for dim in dims_to_reduce if input_shape[dim] != 1]
+
+        has_symbolic_reduce_dim = any(
+            isinstance(input_shape[dim], torch.SymInt) for dim in dims_to_reduce
+        )
+        if has_symbolic_reduce_dim and get_quantization(x.node.target) is not None:
+            raise NotImplementedError(
+                "Quantized mean.dim with symbolic reduced dimensions is not supported"
+            )
 
         view_op = get_view(op)
 
+        if not has_symbolic_reduce_dim:
+            # for static shapes we should ensure that we only keep non 1 dimensions.
+            dims_to_reduce = [dim for dim in dims_to_reduce if input_shape[dim] != 1]
+
         # Reshape to 4D
         if len(input_shape) != 4:
             new_shape = copy(input_shape)
@@ -140,26 +169,66 @@ def call_operator(self, op, args, kwargs, meta):
             x = self._maybe_insert_q_dq_after(x, meta)
 
         # Reduce (h,w) dims by avg pool if possible
-        x, dims_to_reduce = self._reduce_by_average_pool(op, x, dims_to_reduce, meta)
+        if not has_symbolic_reduce_dim:
+            x, dims_to_reduce = self._reduce_by_average_pool(
+                op, x, dims_to_reduce, meta
+            )
 
         # Reshape back to 5D if necessary
         if len(input_shape) > 4:
-            original_dims = input_shape[0:-3]
+            original_dims = input_shape[:-3]
             temp_shape = list(x.data.shape)[1:]
             temp_shape = original_dims + temp_shape
             dims_to_reduce = [dim + len(original_dims) - 1 for dim in dims_to_reduce]
 
             x = super().call_operator(view_op, (x, temp_shape), {}, meta, True)
             x = self._maybe_insert_q_dq_after(x, meta)
-        # Reduce remaining dims by sum
-        x = self._reduce_by_sum(op, x, dims_to_reduce, meta)
+
+        if has_symbolic_reduce_dim:
+            x = self._reduce_by_sum_symbolic(op, x, dims_to_reduce, meta)
+        else:
+            x = self._reduce_by_sum(op, x, dims_to_reduce, meta)
 
         # Reshape to correct output shape if necessary
         if list(x.data.shape) != output_shape:
             x = super().call_operator(view_op, (x, output_shape), {}, meta, True)
 
         return x
 
+    def _reduce_by_sum_symbolic(self, op, input_node, dims, meta):
+        input_shape = input_node.data.size()
+        reduced_shape = [input_shape[dim] for dim in dims]
+
+        sum_op, mul_op, full_op, recip_op, expand_op = (
+            get_dynamic_meandim_decomposition(op)
+        )
+
+        sum = super().call_operator(sum_op, (input_node, dims, True), {}, meta, True)
+
+        ones = super().call_operator(
+            full_op,
+            ([1], 1.0),
+            {"dtype": meta.data["val"].dtype, "device": input_node.data.device},
+            meta,
+            True,
+        )
+        expanded_ones = super().call_operator(
+            expand_op,
+            (ones, reduced_shape),
+            {},
+            meta,
+            True,
+        )
+        counts = super().call_operator(
+            sum_op,
+            (expanded_ones, list(range(len(reduced_shape))), True),
+            {},
+            meta,
+            True,
+        )
+        recip = super().call_operator(recip_op, (counts,), {}, meta, True)
+        return super().call_operator(mul_op, (sum, recip), {}, meta, True)
+
     def _reduce_by_sum(self, op, input_node, dims, meta):
         if len(dims) == 0:
             return input_node
@@ -224,13 +293,9 @@ def _reduce_by_average_pool(self, op, input_node, dims, meta):
         if is_supported:
             out = super().call_operator(avgpool_op, args, {}, meta, True)
             out = self._maybe_insert_q_dq_after(out, meta)
-            return (
-                out,
-                dims_to_reduce_by_sum,
-            )
+            return out, dims_to_reduce_by_sum
 
-        else:
-            return input_node, dims
+        return input_node, dims
 
     def _maybe_insert_q_dq_after(self, op, meta):
         """If the input node of op is a dequant node, insert a q-dq pair after
@@ -242,20 +307,18 @@ def _maybe_insert_q_dq_after(self, op, meta):
                 f"Expected one input to {op.node}, got inputs {op.node.all_input_nodes}"
             )
         input_node = op.node.all_input_nodes[0]
-        if (quant_ops := get_quantization(input_node.target)) is not None:
-            q_op, dq_op = quant_ops
-            quant_args = list(input_node.args[1:])
-            q_args = (op, *quant_args)
-            out = super().call_operator(
-                q_op,
-                q_args,
-                kwargs={},
-                meta=meta,
-                updated=True,
-            )
-            dq_args = (out, *quant_args)
-            return super().call_operator(
-                dq_op, dq_args, kwargs={}, meta=meta, updated=True
-            )
-        else:
+        if (quant_ops := get_quantization(input_node.target)) is None:
             return op
+
+        q_op, dq_op = quant_ops
+        quant_args = list(input_node.args[1:])
+        q_args = (op, *quant_args)
+        out = super().call_operator(
+            q_op,
+            q_args,
+            kwargs={},
+            meta=meta,
+            updated=True,
+        )
+        dq_args = (out, *quant_args)
+        return super().call_operator(dq_op, dq_args, kwargs={}, meta=meta, updated=True)