Rotate Left in an 8-bit Register

Code

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

uint8_t rotate_left(uint8_t reg, uint8_t n) {
    uint8_t tmp = 1; tmp << n; tmp -= 1; tmp <<= 8 - n;
    tmp |= reg; reg <<=n; tmp >>= 8 - n;
    return tmp | reg;
}

int main() {
    uint8_t reg, n;
    scanf("%hhu %hhu", &reg, &n);
    printf("%u", rotate_left(reg, n));
    return 0;
}

Solving Approach