cmp_f80

pub inline fn cmp_f80(comptime RT: type, a: f80, b: f80) RT

File

Code

pub inline fn cmp_f80(comptime RT: type, a: f80, b: f80) RT {
    const a_rep = std.math.F80.fromFloat(a);
    const b_rep = std.math.F80.fromFloat(b);
    const sig_bits = std.math.floatMantissaBits(f80);
    const int_bit = 0x8000000000000000;
    const sign_bit = 0x8000;
    const special_exp = 0x7FFF;

    // If either a or b is NaN, they are unordered.
    if ((a_rep.exp & special_exp == special_exp and a_rep.fraction ^ int_bit != 0) or
        (b_rep.exp & special_exp == special_exp and b_rep.fraction ^ int_bit != 0))
        return RT.Unordered;

    // If a and b are both zeros, they are equal.
    if ((a_rep.fraction | b_rep.fraction) | ((a_rep.exp | b_rep.exp) & special_exp) == 0)
        return .Equal;

    if (@intFromBool(a_rep.exp == b_rep.exp) & @intFromBool(a_rep.fraction == b_rep.fraction) != 0) {
        return .Equal;
    } else if (a_rep.exp & sign_bit != b_rep.exp & sign_bit) {
        // signs are different
        if (@as(i16, @bitCast(a_rep.exp)) < @as(i16, @bitCast(b_rep.exp))) {
            return .Less;
        } else {
            return .Greater;
        }
    } else {
        const a_fraction = a_rep.fraction | (@as(u80, a_rep.exp) << sig_bits);
        const b_fraction = b_rep.fraction | (@as(u80, b_rep.exp) << sig_bits);
        if ((a_fraction < b_fraction) == (a_rep.exp & sign_bit == 0)) {
            return .Less;
        } else {
            return .Greater;
        }
    }
}