zig/std/special/compiler_rt/umodti3.zig

const __udivmodti4 = @import("udivmodti4.zig").__udivmodti4;
const builtin = @import("builtin");
const linkage = if (builtin.is_test) builtin.GlobalLinkage.Internal else builtin.GlobalLinkage.LinkOnce;

export fn __umodti3(a: u128, b: u128) -> u128 {
    @setDebugSafety(this, builtin.is_test);
    @setGlobalLinkage(__umodti3, linkage);
    var r: u128 = undefined;
    _ = __udivmodti4(a, b, &r);
    return r;
}