* toplev.c (rest_of_compilation): find_loop_tree_blocks before
remove_unnecessary_notes.
(debug_ignore_block): New fn.
* toplev.h: Declare it.
* emit-rtl.c (remove_unncessary_notes): Call it.
* dwarf2out.c (dwarf2out_ignore_block): New fn.
* dwarf2out.h: Declare it.
* final.c (final_start_function): Don't call remove_unnecessary_notes
if we did insn scheduling.