Write C++20 char array without branching (I)

#include <bit>
#include <bitset>
#include <iostream>

        char*         a = "abcdef";
        unsigned int  i = 0;
        unsigned int  k = 1;            // k to be determined

int main() {
        start:
            int b = std::popcount( std::uint8_t(a[i]) ) * k;
            __asm__ ("jmp done+b");
        done:
            goto exit;
        print:
            __asm__ ("nop");            // fill in with
            __asm__ ("nop");            // 8*k nops
            __asm__ ("nop");
            __asm__ ("nop");
            __asm__ ("nop");
            __asm__ ("nop");
            __asm__ ("nop");
            __asm__ ("nop");
            std::cout << a[i++]; goto start;
        exit:
            std::cout << "\n";
            return 0;
}