[tree-ssa] Removal of unused vars

[Jason Merrill]

On Wed, 25 Jun 2003 19:03:27 -0600, law@redhat.com wrote:

> This patch allows us to eliminate a large number of the unused variables
> before handing the function off to the tree->rtl translators.

Hmm.  Doing this for the temporaries is great, but for debugging I think we
want to retain user vars so long as we haven't killed their entire scope.
Even if all we can say in the debugger is <optimized away>, we need to
remember the name.

Maybe check DECL_ARTIFICIAL unless >= -O2?

Jason