"I'm talking about free compilers (no cost i mean)."

Press the 'Links' button.

Beware: These "free" compilers are not necessarily "no cost" - they often require you to do a lot more work to get them working, may not have such a "polished" interface, may not produce code quite up to the standard of the paid-for versions, may not be supported, etc, ...
See this post on "Value For Money"

Try a search here and see what others have said about SDCC.

You will need to make your own decision as to whether any particular tool meets your particular cost, performance, and any other requirements.