Branch-free detection of sign

I found something wrong in the following video,

https://www.youtube.com/watch?v=Z59REm2YKX0

The branch free code by author is,

bool OppositeSign(int a, int b) {

    return (a ^ b) < 0;

}

But the compiler can internally convert the statement "return (a ^ b) < 0;" into conditional code.

Here is a branch free code, if the processor provide bit manipulation instructions (most of the processors provide)

// except inputs every thing is compile time constant

bool OppositeSign(int a, int b) {

    unsigned const shift = sizeof(int)*8-1;

    unsigned const mask  = 1 << shift;

   

    return unsigned((a&mask)^(b&mask)) >> shift;

}