[FIRRTL] Add a missing unrealized conversion cast in LowerClasses #9005
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The `updateObjectInClass` function replaces all `firrtl.object` ops with `om.object` ops before any dialect conversion is done. Doing so replaces a `!firrtl.class<...>` with a `!om.class.type<...>`, which leads to invalid IR and the `WireOp` lowering later crashing because it asks a `firrtl.propassign` for its source operand, which is expected to be a FIRRTL type, which then crashes in an assertion failure. To avoid this, add an `unrealized_conversion_cast` op to map the `!om.class.type<...>` back to `!firrtl.class<...>`, and then eliminate the cast during the dialect conversion.
mikeurbach
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Sep 23, 2025
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mikeurbach
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This makes sense to me, thanks for bringing in the casts.
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The
updateObjectInClassfunction replaces allfirrtl.objectops withom.objectops before any dialect conversion is done. Doing so replaces a!firrtl.class<...>with a!om.class.type<...>, which leads to invalid IR and theWireOplowering later crashing because it asks afirrtl.propassignfor its source operand, which is expected to be a FIRRTL type, which then crashes in an assertion failure.To avoid this, add an
unrealized_conversion_castop to map the!om.class.type<...>back to!firrtl.class<...>, and then eliminate the cast during the dialect conversion.