How Clang recognizes your popcount loop and swaps it for a single CPU instruction
jimmykoppel · x · 2026-10-27
Jimmy Koppel shares a deep-dive on compiler optimization: when you write a loop that counts 1-bits in a number, Clang throws the loop away and replaces it with the chip's native popcount instruction. The piece explains how the compiler recognizes your loop's semantics and performs this rewrite.
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