ARM Introduces FEAT_CSSC: Native Popcount for General-Purpose Registers

lemire · x · 2026-08-01

The author discusses the Common Short Sequence Compression (FEATCSSC) extension recently added to the ARM instruction set.

Previously, performing a population count on a general-purpose register in ARM required moving data back and forth into SIMD registers using the CNT instruction. The new FEATCSSC extension allows the CNT instruction to operate directly on general-purpose registers, greatly streamlining low-level optimization workflows.

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