RTL处理及优化_rtl优化-优快云博客

本文链接：https://blog.youkuaiyun.com/swh547/article/details/139381890

RTL处理及优化

在all_passes链中，执行了pass_expand过程之后，GCC的中间表示就已经转换成RTL形式，此后的所有处理都是基于RTL的处理过程，即RTL_PASS。
所有的RTL处理都包含在pass_rest_of_compilation的处理过程以及子过程中，主要包含对pass_expand所生成的insn序列进行进一步的处理： 循环优化、指令调度、寄存器分配、窥孔优化

RTL的处理过程

基于RTL中间表示进行的处理过程主要包括以下的Pass：

  NEXT_PASS (pass_rest_of_compilation);
    {
      struct opt_pass **p = &pass_rest_of_compilation.pass.sub;
      NEXT_PASS (pass_init_function);
      NEXT_PASS (pass_jump);
      NEXT_PASS (pass_rtl_eh);
      NEXT_PASS (pass_initial_value_sets);
      NEXT_PASS (pass_unshare_all_rtl);
      NEXT_PASS (pass_instantiate_virtual_regs);
      NEXT_PASS (pass_into_cfg_layout_mode);
      NEXT_PASS (pass_jump2);
      NEXT_PASS (pass_lower_subreg);
      NEXT_PASS (pass_df_initialize_opt);
      NEXT_PASS (pass_cse);
      NEXT_PASS (pass_rtl_fwprop);
      NEXT_PASS (pass_gcse);
      NEXT_PASS (pass_rtl_ifcvt);
      /* Perform loop optimizations.  It might be better to do them a bit
	 sooner, but we want the profile feedback to work more
	 efficiently.  */
      NEXT_PASS (pass_loop2);
	{
	  struct opt_pass **p = &pass_loop2.pass.sub;
	  NEXT_PASS (pass_rtl_loop_init);
	  NEXT_PASS (pass_rtl_move_loop_invariants);
	  NEXT_PASS (pass_rtl_unswitch);
	  NEXT_PASS (pass_rtl_unroll_and_peel_loops);
	  NEXT_PASS (pass_rtl_doloop);
	  NEXT_PASS (pass_rtl_loop_done);
	  *p = NULL;
	}
      NEXT_PASS (pass_web);
      NEXT_PASS (pass_jump_bypass);
      NEXT_PASS (pass_cse2);
      NEXT_PASS (pass_rtl_dse1);
      NEXT_PASS (pass_rtl_fwprop_addr);
      NEXT_PASS (pass_reginfo_init);
      NEXT_PASS (pass_inc_dec);
      NEXT_PASS (pass_initialize_regs);
      NEXT_PASS (pass_outof_cfg_layout_mode);
      NEXT_PASS (pass_ud_rtl_dce);
      NEXT_PASS (pass_combine);
      NEXT_PASS (pass_if_after_combine);
      NEXT_PASS (pass_partition_blocks);
      NEXT_PASS (pass_regmove);
      NEXT_PASS (pass_split_all_insns);
      NEXT_PASS (pass_lower_subreg2);
      NEXT_PASS (pass_df_initialize_no_opt);
      NEXT_PASS (pass_stack_ptr_mod);
      NEXT_PASS (pass_mode_switching);
      NEXT_PASS (pass_see);
      NEXT_PASS (pass_match_asm_constraints);
      NEXT_PASS (pass_sms);
      NEXT_PASS (pass_sched);
      NEXT_PASS (pass_subregs_of_mode_init);
      NEXT_PASS (pass_ira);
      NEXT_PASS (pass_subregs_of_mode_finish);
      NEXT_PASS (pass_postreload);
	{
	  struct opt_pass **p = &pass_postreload.pass.sub;
	  NEXT_PASS (pass_postreload_cse);
	  NEXT_PASS (pass_gcse2);
	  NEXT_PASS (pass_split_after_reload);
	  NEXT_PASS (pass_branch_target_load_optimize1);
	  NEXT_PASS (pass_thread_prologue_and_epilogue);
	  NEXT_PASS (pass_rtl_dse2);
	  NEXT_PASS (pass_rtl_seqabstr);
	  NEXT_PASS (pass_stack_adjustments);
	  NEXT_PASS (pass_peephole2);
	  NEXT_PASS (pass_if_after_reload);
	  NEXT_PASS (pass_regrename);
	  NEXT_PASS (pass_cprop_hardreg);
	  NEXT_PASS (pass_fast_rtl_dce);
	  NEXT_PASS (pass_reorder_blocks);
	  NEXT_PASS (pass_branch_target_load_optimize2);
	  NEXT_PASS (pass_leaf_regs);
	  NEXT_PASS (pass_split_before_sched2);
	  NEXT_PASS (pass_sched2);
	  NEXT_PASS (pass_stack_regs);
	    {
	      struct opt_pass **p = &pass_stack_regs.pass.sub;
	      NEXT_PASS (pass_split_before_regstack);
	      NEXT_PASS (pass_stack_regs_run);
	    }
	  NEXT_PASS (pass_compute_alignments);
	  NEXT_PASS (pass_duplicate_computed_gotos);
	  NEXT_PASS (pass_variable_tracking);
	  NEXT_PASS (pass_free_cfg);
	  NEXT_PASS (pass_machine_reorg);
	  NEXT_PASS (pass_cleanup_barriers);
	  NEXT_PASS (pass_delay_slots);
	  NEXT_PASS (pass_split_for_shorten_branches);
	  NEXT_PASS (pass_convert_to_eh_region_ranges);
	  NEXT_PASS (pass_shorten_branches);
	  NEXT_PASS (pass_set_nothrow_function_flags);
	  NEXT_PASS (pass_final);
	}
      NEXT_PASS (pass_df_finish);
    }
  NEXT_PASS (pass_clean_state);
  *p = NULL;