[CuTeDSL] Make @cute.struct instances flattenable across scf.if / scf.while#3270
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cheshire wants to merge 1 commit into
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[CuTeDSL] Make @cute.struct instances flattenable across scf.if / scf.while#3270cheshire wants to merge 1 commit into
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….while Fixes NVIDIA#3268 A `@cute.struct` instance captured into an `scf.if` branch or `scf.while` body fails the DSL trace with: DSLRuntimeError: The 'if' statement encountered a user-defined Python object, which cannot be automatically converted into an dynamic expression. This blocks the natural warp-specialization pattern, where each `if warp_idx == <role>:` branch reads its tile from a shared storage struct. A struct instance is fully described by its `base` pointer (already DynamicExpression-aware via `_Pointer`); every field instance is re-derived from `base + static offsets` on construction. Implement the DynamicExpression protocol on each decorated class by forwarding `__get_mlir_types__` / `__extract_mlir_values__` to `base`, and `__new_from_mlir_values__` to a fresh decorator invocation that re-derives the fields from a rebuilt base pointer. Tested in Docker on cutlass-dsl 4.5.1 with six new unit tests in test/python/CuTeDSL/test_struct_in_if.py covering: * the original failing case (storage.get_tensor inside dynamic if), * regression: plain non-branched struct usage still works, * nested struct (struct-of-struct) inside a dynamic if, * if/else with both branches accessing the struct, * if/elif/elif/else (the actual warp-specialization shape), * scf.while body capturing the struct.
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LGTM @grypp to double check |
grypp
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May 27, 2026
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Looks good to me. Thanks for contributing
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we could add a test with union as well.
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I'll add one when landing this internally
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Fixes #3268
A
@cute.structinstance captured into anscf.ifbranch orscf.whilebody fails the DSL trace with:This blocks the natural warp-specialization pattern, where each
if warp_idx == <role>:branch reads its tile from a shared storage struct.A struct instance is fully described by its
basepointer (already DynamicExpression-aware via_Pointer); every field instance is re-derived frombase + static offsetson construction. Implement the DynamicExpression protocol on each decorated class by forwarding__get_mlir_types__/__extract_mlir_values__tobase, and__new_from_mlir_values__to a fresh decorator invocation that re-derives the fields from a rebuilt base pointer.