fn add(a: u32, b: u32) void {
    const c = a + b; // 7
    const d = a + c; // 10
    const e = d + b; // 14
    assert(e == 14);
}

// generated ZIR:

@add = fn(@unnamed$9, {
  %0 = arg()
  %1 = arg()
  %2 = add(%0, %1)
  %3 = add(%0, %2)
  %4 = add(%3, %1)
  %5 = cmp(%4, eq, @unnamed$6)
  %6 = call(@assert, [%5], modifier=auto)
  %7 = returnvoid()
})

[nix-shell:~/dev/zig/build-release]$ ./zig-cache/bin/zig build-exe test.zig -femit-zir
test.zig:7:16: error: TODO implement copyToNewRegister