* lower-subreg.c: Include except.h.
(decompose_multiword_subregs): Verify that the only control flow
insns we can split are loads to multi-words pseudos.
Handle breaking such blocks after splitting, instead of calling
find_many_sub_basic_blocks.
* loop-unroll.c (split_edge_and_insert): Don't set BB_SUPERBLOCK
on the new basic block. Add a lengthy comment explaining why we
thought this was necessary.
* cfglayout.c (cfg_layout_finalize): Don't break superblocks.