[PATCH] Allow DCE of const or pure calls

[Eric Botcazou]

> So I think this is fixing a regression from 3.4 on a RTL level
> optimization.

Note that, with this reasoning, every optimization that has been moved from 
RTL to Tree level is the source of a regression from 3.4.  But users cannot 
tell the difference between Tree level and RTL level optimizations, and DCE
of const or pure calls should already happen at the Tree level.

-- 
Eric Botcazou