Pulled from bullet source code:

unsigned btSelect(unsigned condition, unsigned valueIfConditionNonZero, unsigned valueIfConditionZero) 
{
    // Set testNz to 0xFFFFFFFF if condition is nonzero, 0x00000000 if condition is zero
    // Rely on positive value or'ed with its negative having sign bit on
    // and zero value or'ed with its negative (which is still zero) having sign bit off 
    // Use arithmetic shift right, shifting the sign bit through all 32 bits
    unsigned testNz = (unsigned)(((int)condition | -(int)condition) >> 31);
    unsigned testEqz = ~testNz;
    return ((valueIfConditionNonZero & testNz) | (valueIfConditionZero & testEqz)); 
}

https://c.godbolt.org/z/rMf6Ta613

The following code doesn't get simplified:

define i8 @src(i8 %a0, i8 %a1, i8 %a2) {
  %add = add i8 %a0, -1
  %xor = xor i8 %a0, -1
  %and = and i8 %add, %xor
  %cmp = icmp sgt i8 %and, -1
  %sel = select i1 %cmp, i8 %a1, i8 %a2
  ret i8 %sel
}

define i8 @tgt(i8 %a0, i8 %a1, i8 %a2) {
  %cmp = icmp ne i8 %a0, 0
  %sel = select i1 %cmp, i8 %a1, i8 %a2
  ret i8 %sel
}

Transformation seems to be correct!