Add count_zeros() and count_ones() (lane-wise popcnt) - #345
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LaurenzV
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Aug 25, 2026
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The API mirrors std::simd. Unlike std::simd, we return
Selffrom all vector types rather than creating anUnsignedassociated type and returning that. The counts always fit into the signed values, and this simplifies generic code a lot. Vectors can be explicitly bitcast if the unsigned variant is needed.The lowerings for u8/i8 and u64/i64 are identical to std::simd; for u16 and u32 we have 1.5x to 2x better throughput but worse latency (9 vs 7 cycles for u16, 14 vs 12 for u32), which seems fine for SIMD code.
Closes #341