Which optimisations are are easier or perhaps only possible in the frontend ?

[Stefan Koch via Digitalmars-d]

On Thursday, 11 December 2014 at 10:59:24 UTC, Daniel Murphy 
wrote:

> Why?  If the inliner is out because of DMD's merging process, 
> then so is the rest of the frontend.

It is not out!

But my question was not about dmd specific things, I meant it 
more generally.