3.74

Solution

This is the solution, with inline asm code in C:

range_t find_range(float x)
{
    __asm__(
        "vxorps %xmm1, %xmm1, %xmm1\n"
        "vucomiss %xmm1, %xmm0\n"
        "movl $3, %edx\n"
        "movl $2, %ecx\n"
        "movl $1, %edi\n"
        "movl $0, %esi\n"
        "cmova %ecx, %eax\n"
        "cmove %edi, %eax\n"
        "cmovb %esi, %eax\n"
        "cmovp %edx, %eax\n"
    );
}

The complete C file, along with checks over all \(2^{32}\) values can be found here.