[tree-ssa] RFC: Making control flow more explicit

[law@redhat.com]

In message <1060297370.10825.94.camel@frodo.toronto.redhat.com>, Diego Novillo 
writes:
 >On Thu, 2003-08-07 at 17:06, Jason Merrill wrote:
 >
 >> Is that a problem?  What would be the benefit of delaying the move to SSA
 >> form?
 >> 
 >So far the problems have been in stability more than anything.  Since
 >some forms of control are still hidden by the IL, doing some things like
 >sticking a label at an arbitrary spot in the code to make other parts
 >unreachable, leads to problems.  This was something that Jeff Law
 >recently ran into when doing some of the control transformations he's
 >been implementing.
FWIW, my problem is a combination of a problem with our container based
linkage of statements and our nested control structures.    We've got
a container in the IL which has a dangling pointer to a de-linked basic
block. 

As it turns out that mostly mucks up tree dumping and not real code, but
it's still extremely annoying.  I thought I had it fixed, but the changes
caused problems elsewhere.

Jeff