What LDC flags should be used to get the fastest executable on Windows?

[Preetpal]

On Saturday, 6 March 2021 at 10:51:35 UTC, Preetpal wrote:
> On Saturday, 6 March 2021 at 09:07:05 UTC, Imperatorn wrote:
>> There's not much going on in the code there. Where are you 
>> experiencing problems? Have you profiled it?
>
> As it is small program, I re-implemented it in C 
> (https://gist.github.com/preetpalS/81405cd78ade738034cfa6d49e2a4202) to see if it could reduce the problem I was seeing. Based on my observations it did reduce the problem but it did not eliminate it. This led me to believe that the issue I was seeing in the D version was performance-related.

I just really want to be sure that the D version of the program 
can match the C version of the program.