[otp_ctrl] Expand overly wide literals (vectors) #26998
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LRM 6.9.1 says vectors (constant literals) may not exceed an implementation-defined width, which Verilator defaults to 2^16. Expand overly wide vectors into a concatenation of narrower vectors. Addresses lowRISC#26883. Signed-off-by: Quan Nguyen <[email protected]>
rswarbrick
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Apr 17, 2025
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This looks like a really good way to do things! I'd suggest a couple of slight tweaks:
- Change the commit message to mention the fact that the implementation-defined width is guaranteed to be at least 2^16 (which is why this change is guaranteed to work).
- Drop the
max_widthargument fromexpand_literal: I doubt we'll ever want a different value. - Remove the outer cast from the result: we're already adding zeros to the MSB to ensure the width is correct anyway.
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Full investigation into the maximum literal/bit-vector widths added as a comment to #27069 where two alternative approaches are under discussion. I shall not replicate it here. |
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LRM 6.9.1 says vectors (constant literals) may not exceed an implementation-defined width, which Verilator defaults to 2^16. While Verilator's internal limit can be overridden with
--max-num-width, this PR nevertheless expands overly wide vectors into a concatenation of narrower vectors. Addresses #26883.