Do not save hash slots across calls to hash_table::get_or_insert.

Do not save hash slots across calls to hash_table::get_or_insert.

There's a read of a freed block while accessing the default_slot in
calc_switch_ranges.

      default_slot->intersect (def_range);

It seems the default_slot got swiped from under us, and the valgrind
dump indicates the free came from the get_or_insert in the same
function:

      irange *&slot = m_edge_table->get_or_insert (e, &existed);

So it looks like the get_or_insert is actually freeing the value of
the previously allocated default_slot.  Looking down the chain
from get_or_insert, we see it calls hash_table<>::expand, which
actually does a free while doing a resize of sorts:

  if (!m_ggc)
    Allocator <value_type> ::data_free (oentries);
  else
    ggc_free (oentries);

This patch avoids keeping a pointer to the default_slot across multiple
calls to get_or_insert in the loop.

gcc/ChangeLog:

	PR tree-optimization/97379
	* gimple-range-edge.cc (outgoing_range::calc_switch_ranges): Do
	not save hash slot across calls to hash_table<>::get_or_insert.