[nix-shell:~/Downloads/zig/build]$ cat test2.zig 
export fn sum(N: u64) u64 {
    var s: u64 = 0;
    var i: u64 = 0;
    while (i < N) : (i += 1) {
        s +%= i;
    }
    return s;
}

[nix-shell:~/Downloads/zig/build]$ ./zig build-obj test2.zig --release-fast -target riscv64-freestanding --bundle-compiler-rt

[nix-shell:~/Downloads/zig/build]$ ~/local/llvm9-release/bin/llvm-objdump -d test2.o  | grep multi3
Disassembly of section .text.__multi3:
0000000000000000 __multi3: