IRGen: Fix extra inhabitants of multi-payload enums with more spare bits than tag bits. #21065
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@swift-ci Please test |
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This looks good to me. What happens when we just have extra tag bits and no common spare bits? We use the full byte(s) for the extra inhabitants. Don't we have the same problem in this case? |
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No, in that case the extra tag value always uses the entire byte/word. |
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@swift-ci Please clean test Linux |
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…its than tag bits. Because layout minimizes the number of tag bits used, and favors high spare bits, the spare bit representations end up overlapping the extra inhabitant representations, since we just counted down from -1. If there are fewer tag bits than total spare bits, rotate the extra inhabitant values so they correctly line up with the tag representations in this situation. rdar://problem/46468090
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Because layout minimizes the number of tag bits used, and favors high spare bits, the
spare bit representations end up overlapping the extra inhabitant representations, since we
just counted down from -1. If there are fewer tag bits than total spare bits, rotate the
extra inhabitant values so they correctly line up with the tag representations in this
situation. rdar://problem/46468090