[Custom Descriptors] Better handle unreachable ref.cast_desc #7937
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Validate that the descriptor operand of ref.cast_desc is always a descriptor reference (or a nullref or unreachable), even if the ref operand and therefore the ref.cast_desc are unreachable. This removes an edge case passes might otherwise have to consider where the descriptor operand is not actually a descriptor. Update GTO to preserve this new validation invariant. Also print an unreachable ref.cast_desc instruction when we can determine its type from a concrete, non-null descriptor operand rather than bailing out and printing an unreachable block. This allows us to preserve such IR through text round trips, which can help e.g. test case reduction.
kripken
approved these changes
Oct 1, 2025
|
Going to merge without heavy additional fuzzing because this is on the path to fixing the descriptor type validation rules, which have been causing many fuzzer failures for me. |
tlively
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that referenced
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Oct 1, 2025
Do not leave unreachable ref.cast_desc instructions with descriptors arguments that have been optimized to no longer be descriptors. This was intended to be inluded in #7937.
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Ugh, and of course I now notice I forgot to actually commit the GTO fix: #7938. |
tlively
added a commit
that referenced
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Oct 2, 2025
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Validate that the descriptor operand of ref.cast_desc is always a
descriptor reference (or a nullref or unreachable), even if the ref
operand and therefore the ref.cast_desc are unreachable. This removes an
edge case passes might otherwise have to consider where the descriptor
operand is not actually a descriptor. Update GTO to preserve this new
validation invariant.
Also print an unreachable ref.cast_desc instruction when we can
determine its type from a concrete, non-null descriptor operand rather
than bailing out and printing an unreachable block. This allows us to
preserve such IR through text round trips, which can help e.g. test case
reduction.