Pext zig

pext.zig

inline fn pext(src: anytype, mask: @TypeOf(src)) @TypeOf(src) {
    switch (@TypeOf(src)) {
        u32, u64 => {},
        else => @compileError(std.fmt.comptimePrint("pext called with a bad type: {}\n", .{@TypeOf(src)})),
    }

    if (@inComptime()) {
        @setEvalBranchQuota(std.math.maxInt(u32));
        var result: @TypeOf(src) = 0;
        var m = mask;
        var i: std.math.Log2Int(@TypeOf(src)) = 0;
        while (m > 0) : ({
            m &= m -% 1;
            i += 1;
        }) {
            result |= ((src >> @ctz(m)) & 1) << i;
        }
        return result;
    }

    return asm ("pext %[mask], %[src], %[ret]"
        : [ret] "=r" (-> @TypeOf(src)),
        : [src] "r" (src),
          [mask] "r" (mask),
    );
}