Zig 0.17.0-dev (Split by item)

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muldXi

mulXi3.muldXi

pub fn muldXi(comptime T: type, a: T, b: T) DoubleInt(T)

File

lib/compiler_rt/mulXi3.zig:62

Code

pub fn muldXi(comptime T: type, a: T, b: T) DoubleInt(T) {
    const DT = DoubleInt(T);
    const word_t = compiler_rt.HalveInt(DT, false);
    const bits_in_word_2 = @sizeOf(T) * 8 / 2;
    const lower_mask = (~@as(T, 0)) >> bits_in_word_2;

    var r: word_t = undefined;
    r.s.low = (a & lower_mask) *% (b & lower_mask);
    var t: T = r.s.low >> bits_in_word_2;
    r.s.low &= lower_mask;
    t += (a >> bits_in_word_2) *% (b & lower_mask);
    r.s.low +%= (t & lower_mask) << bits_in_word_2;
    r.s.high = t >> bits_in_word_2;
    t = r.s.low >> bits_in_word_2;
    r.s.low &= lower_mask;
    t +%= (b >> bits_in_word_2) *% (a & lower_mask);
    r.s.low +%= (t & lower_mask) << bits_in_word_2;
    r.s.high +%= t >> bits_in_word_2;
    r.s.high +%= (a >> bits_in_word_2) *% (b >> bits_in_word_2);
    return r.all;
}