PR rtl-optimization/32300
* see.c (see_copy_insn): New function.
(see_def_extension_not_merged, see_merge_one_use_extension,
see_merge_one_def_extension): Use it. Avoid changing
PREV_INSN/NEXT_INSN chains directly, insted emit insns
into sequences. Call df_insn_delete on temporary insns
that won't be emitted into the insn stream.
(rest_of_handle_see): Turn off DF_DEFER_INSN_RESCAN
and run df_process_deferred_rescans () before run_fast_dce.
From-SVN: r128108
