And here is the patch that breaks things. By moving df_defs_record() 
*after* df_get_call_refs() most times collection_rec remains sorted, and 
about 50M instructions are avoided in qsort() 
calls of df_canonize_collection_rec().

Unfortunately this does not work. Sometimes cc1 crashes, for example 
because regstack is empty in subst_stack_regs_in_debug_insn().

Any ideas for ensuring proper ordering of collection_rec?


Thanks,
Dimitris