https://en.wikipedia.org/wiki/Hacker%27s_Delight

> On the other hand, if you prefer the result be either -1, 0, or +1, then use:

> sign = (v != 0) | -(int)((unsigned int)((int)v) >> (sizeof(int) * CHAR_BIT - 1));

> // Or, for more speed but less portability:

> sign = (v != 0) | (v >> (sizeof(int) * CHAR_BIT - 1)); // -1, 0, or +1

> // Or, for portability, brevity, and (perhaps) speed:

> sign = (v > 0) - (v < 0); // -1, 0, or +1

Or if you prefer portability, speed, and readability at the same time:

    int sign(int i) {
        if(i > 0)
            return 1;
        else if(i < 0)
            return -1;
        else
            return 0;
    }

        mov     ecx, edi
        sar     ecx, 31
        test    edi, edi
        mov     eax, 1
        cmovle  eax, ecx
        ret

(still useful as a reference for implementing an optimizer, to be read as pseudo code)

http://www.hakmem.org/