[Bug rtl-optimization/81194] [8 Regression] ICE during RTL pass: expand

["bergner at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81194

--- Comment #12 from Peter Bergner <bergner at gcc dot gnu.org> ---
(In reply to Peter Bergner from comment #11)
> (In reply to Peter Bergner from comment #10)
> > I'm testing the attached patch which fixes the ICE.
> 
> Except this ICEs on the following simple test case.  I'll see if this is due
> to a simple oversite or ...
[snip]
> It seems cleanup_tree_cfg() has removed the entire function at this point.

So with no function body, build_gimple_cfg() calls make_edges() and it contains
an assumption that there will be a block in the function with this code:

  /* Create an edge from entry to the first block with executable
     statements in it.  */
  make_edge (ENTRY_BLOCK_PTR_FOR_FN (cfun),
             BASIC_BLOCK_FOR_FN (cfun, NUM_FIXED_BLOCKS),
             EDGE_FALLTHRU);

but in this case, there is no block numbered NUM_FIXED_BLOCKS which causes
find_edge to ICE.