C++ PATCH: perform_implicit_conversion

[Jason Merrill]

>>>>> Mark Mitchell <mark@codesourcery.com> writes:

>>>>> "Nathan" == Nathan Sidwell <nathan@acm.org> writes:
 Nathan> That would be optimizing the compiler on the (hopefully)
 Nathan> rare failure path to the detriment of the frequent success
 Nathan> path. Ok, not by much.  implicit_conversion copes with an
 Nathan> error_mark_node and returns NULL. (I should have said
 Nathan> that)

 > Good point.  But, we're so far from having any idea where the
 > performance hot spots are in the C++ front-end (and I bet you they're
 > not in implicit_conversion), that I don't think we need to worry about
 > this.  I think simple code is the way to the go, until the compiler is
 > considerably more correct than it is now.

Agreed.  Optimization without reference to a profiler only makes code
harder to maintain.  Didn't Knuth have an aphorism about that?

Jason