Problem with tree-ssa-loop-ivopts.c:get_computation-cost

[Richard Kenner]

This function generates RTL from an expression to see how many RTL insns
it is.  But this causes a problem compiling the Ada ACATS test cxa4006.

The problem is when part of the expression has a location.  In that
case, record_block_change is called and that relies on
cfun->ib_boundaries_block being set.  But it isn't because we aren't
expanding stuff "for real".  A kludge would be to test that field, but
what's the proper way?

Also, seq_cost really should be looking at next_real_insn, not NEXT_INSN,
since any notes shouldn't be counted.