CoreML doesn't handle negative dim values correctly in cumsum

[GregoryComer]

🐛 Describe the bug

Negative dim values other than -1 are not handled correctly on CoreML. It errors out during lowering.

Repro:

import torch

from executorch.backends.apple.coreml.partition import CoreMLPartitioner
from executorch.exir import to_edge_transform_and_lower, EdgeCompileConfig, to_edge
from executorch.extension.pybindings.portable_lib import _load_for_executorch_from_buffer

class Model(torch.nn.Module):
    def __init__(self):
        super().__init__()
        
    def forward(self, x):
        return torch.cumsum(x, dim=-3) # First dim (third from last)

model = Model()
inputs = (
    torch.randn(2, 2, 2),
)

eager_outputs = model(*inputs)
#print(f"Eager: {eager_outputs.shape} {eager_outputs}")

ep = torch.export.export(model.eval(), inputs)
print(ep)

print(f"EP: {ep.module()(*inputs)}")

lowered = to_edge_transform_and_lower(
    ep,
    partitioner=[CoreMLPartitioner()],
    compile_config=EdgeCompileConfig(_check_ir_validity=False)
).to_executorch()

print(lowered.exported_program())

et_model = _load_for_executorch_from_buffer(lowered.buffer)
et_outputs = et_model([*inputs])[0]

et_outputs - eager_outputs

Output:

File [~/miniconda3/envs/executorch/lib/python3.10/site-packages/coremltools/converters/mil/mil/ops/defs/iOS15/tensor_operation.py:166](http://localhost:8888/lab/tree/~/miniconda3/envs/executorch/lib/python3.10/site-packages/coremltools/converters/mil/mil/ops/defs/iOS15/tensor_operation.py#line=165), in cumsum.type_inference(self)
    163 def type_inference(self):
    164     # Check range of axis
    165     if self.axis.val < -1 or self.axis.val > self.x.rank - 1:
--> 166         raise ValueError(
    167             "axis should be in the range [-1, {}]".format(self.x.rank - 1)
    168         )
    170     return self.x.sym_type

ValueError: axis should be in the range [-1, 2]

Versions

coremltools version 8.3
executorch commit 67b6009 (Jun 14)

cc @kimishpatel @YifanShenSZ @cymbalrush @metascroy

[metascroy]

Closing this issue as low-priority. CoreML does not support this op with these args, and this is clear to the user from the error.