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Floating-point tricks provide vectorizable CLZ and CTZ implementations

purplesyringa.moe 4 min read Editor score 7/10

The post derives bit-counting implementations by encoding integers into floating-point values and extracting exponent information. It explores a way to vectorize operations that are not always fast as native instructions.

What

- Floating-point techniques can implement vectorizable count-leading-zeros (CLZ) and count-trailing-zeros (CTZ) operations.

How

- The post describes deriving the counts from floating-point exponents and reports faster vectorized timings on tested Intel CPUs, while AMD may favor scalar code.

Why it matters

- Engineers can use these techniques to explore SIMD alternatives, but should weigh them against target-specific instruction performance.

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