Arm backend: Fix quantized constant-folding for aten.cat lists (#18971)#19064
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perheld merged 1 commit intopytorch:mainfrom Apr 23, 2026
Merged
Arm backend: Fix quantized constant-folding for aten.cat lists (#18971)#19064perheld merged 1 commit intopytorch:mainfrom
perheld merged 1 commit intopytorch:mainfrom
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…ch#18971) FuseConstantArgsPass resolved input_qparams by flattened input-node index, while FoldAndAnnotateQParamsPass stores them by top-level argument index. For aten.cat with a list-valued tensor argument, this caused only the first tensor to be dequantized before folding, which corrupted the fused constant. Resolve qparams by top-level argument index and propagate that qparam through nested list and tuple arguments. Add a regression test for quantized aten.cat constant folding with list-valued tensor inputs. Signed-off-by: Per Held <per.held@arm.com> Change-Id: I6e1a012d82a5dbeecb403c440a2944953dd5cba7
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Pull request overview
Fixes Arm backend constant-folding for quantized ops by aligning how input_qparams are resolved with how they’re produced, specifically for ops like aten.cat where tensor inputs can be nested inside list/tuple arguments.
Changes:
- Update
FuseConstantArgsPassto resolveinput_qparamsby top-level positional argument index (and propagate that qparam through nested list/tuple args). - Add a regression test that constant-folds a quantized
aten.catwhose tensor inputs are passed via a list/tuple.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
backends/arm/_passes/fuse_constant_ops_pass.py |
Fix qparam lookup to use top-level arg index and apply it to nested list/tuple tensor args during constant folding. |
backends/arm/test/passes/test_fuse_constant_ops_pass.py |
Add a regression test ensuring quantized constant-folding for aten.cat with list/tuple tensor inputs produces the correct fused constant. |
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| cat_node = next( | ||
| node | ||
| for node in exported_program.graph_module.graph.nodes | ||
| if node.op == "call_function" |
| exported_program.graph_module | ||
| ) | ||
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| assert list(exported_program.state_dict) == ["aten_cat_default_fused_const"] |
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FuseConstantArgsPass resolved input_qparams by flattened input-node index, while FoldAndAnnotateQParamsPass stores them by top-level argument index. For aten.cat with a list-valued tensor argument, this caused only the first tensor to be dequantized before folding, which corrupted the fused constant.
Resolve qparams by top-level argument index and propagate that qparam through nested list and tuple arguments. Add a regression test for quantized aten.cat constant folding with list-valued tensor inputs.
Change-Id: I6e1a012d82a5dbeecb403c440a2944953dd5cba7
cc @digantdesai @freddan80 @per @zingo @oscarandersson8218 @mansnils @Sebastian-Larsson @robell