Extract Even Bits Only from 32-bit Register

Code

#include <stdio.h>
#include <stdint.h>

uint32_t extract_even_bits(uint32_t reg) {
    uint32_t tmp = 0;
    uint32_t test = 1;
    tmp |= test & reg; test <<= 1; reg >>= 1;
    tmp |= test & reg; test <<= 1; reg >>= 1;
    tmp |= test & reg; test <<= 1; reg >>= 1;
    tmp |= test & reg; test <<= 1; reg >>= 1;
    tmp |= test & reg; test <<= 1; reg >>= 1;
    tmp |= test & reg; test <<= 1; reg >>= 1;
    tmp |= test & reg; test <<= 1; reg >>= 1;
    tmp |= test & reg; test <<= 1; reg >>= 1;
    tmp |= test & reg; test <<= 1; reg >>= 1;
    tmp |= test & reg; test <<= 1; reg >>= 1;
    tmp |= test & reg; test <<= 1; reg >>= 1;
    tmp |= test & reg; test <<= 1; reg >>= 1;
    tmp |= test & reg; test <<= 1; reg >>= 1;
    tmp |= test & reg; test <<= 1; reg >>= 1;
    tmp |= test & reg; test <<= 1; reg >>= 1;
    tmp |= test & reg; test <<= 1; reg >>= 1;
    return tmp;
}

int main() {
    uint32_t reg;
    scanf("%u", &reg);
    printf("%u", extract_even_bits(reg));
    return 0;
}

Solving Approach