<bit> provides bit manipulation utilities introduced in C++20: std::popcount (count set bits), std::countl_zero / std::countr_zero (leading/trailing zeros), std::rotl / std::rotr (rotate), and std::byteswap.

These are thin wrappers around intrinsics like __builtin_popcount, providing portable, consistent semantics without writing assembly.

This example demonstrates counting set bits, counting leading zeros, and rotating bits left, all on an integer value.

// compile: g++ -std=c++20 -o bitexample bitexample.cpp
// run: ./bitexample
// description: bit counting and rotation
 
#include <bit>
#include <iostream>
 
int main() {
    unsigned int x = 0b11010011;
 
    std::cout << "popcount of " << x << ": " << std::popcount(x) << "\n";
    std::cout << "leading zeros: " << std::countl_zero(x) << "\n";
    std::cout << "rotl by 2: " << std::rotl(x, 2) << "\n";
 
    return 0;
}