"The good new compiler would do it efficiently."

Wrong.

Even with Keil, you need to understand the different memory spaces, etc, if you are going to get the most from the processor

I think that all my previous suggestions rely upon this!?

If you ignore these things, the old assembler die-hards will be right: your 'C' will be bloated, slow, and inefficient, and you will have to resort to assembler when things get critical!