Re: -ftree-* options

[Serge Belyshev <belyshev at lubercy dot com>]

>The individual -ftree-* options (e.g., -ftree-pre) state that they are
>enabled at -O and above, yet they are not listed in the description of
>-O1.
>
>I assume they are, indeed, eabled at -O1?

Source code -- best documentation ;-)

opts.c:523:
  if (!optimize)
    {
      flag_merge_constants = 0;
    }

  if (optimize >= 1)
    {
      flag_defer_pop = 1;
      flag_thread_jumps = 1;
#ifdef DELAY_SLOTS
      flag_delayed_branch = 1;
#endif
#ifdef CAN_DEBUG_WITHOUT_FP
      flag_omit_frame_pointer = 1;
#endif
      flag_guess_branch_prob = 1;
      flag_cprop_registers = 1;
      flag_loop_optimize = 1;
      flag_if_conversion = 1;
      flag_if_conversion2 = 1;
      flag_tree_ccp = 1;
      flag_tree_dce = 1;
      flag_tree_dom = 1;
      flag_tree_dse = 1;
      flag_tree_pre = 1;
      flag_tree_ter = 1;
      flag_tree_live_range_split = 1;
      flag_tree_sra = 1;
      flag_tree_copyrename = 1;

      if (!optimize_size)
	{
	  /* Loop header copying usually increases size of the code.  This used
	     not to be true, since quite often it is possible to verify that
	     the condition is satisfied in the first iteration and therefore
	     to eliminate it.  Jump threading handles these cases now.  */
	  flag_tree_ch = 1;
	}
    }

  if (optimize >= 2)
    {
      flag_crossjumping = 1;
      flag_optimize_sibling_calls = 1;
      flag_cse_follow_jumps = 1;
      flag_cse_skip_blocks = 1;
      flag_gcse = 1;
      flag_expensive_optimizations = 1;
      flag_strength_reduce = 1;
      flag_rerun_cse_after_loop = 1;
      flag_rerun_loop_opt = 1;
      flag_caller_saves = 1;
      flag_force_mem = 1;
      flag_peephole2 = 1;
#ifdef INSN_SCHEDULING
      flag_schedule_insns = 1;
      flag_schedule_insns_after_reload = 1;
#endif
      flag_regmove = 1;
      flag_strict_aliasing = 1;
      flag_delete_null_pointer_checks = 1;
      flag_reorder_blocks = 1;
      flag_reorder_functions = 1;
      flag_unit_at_a_time = 1;
    }

  if (optimize >= 3)
    {
      flag_inline_functions = 1;
      flag_unswitch_loops = 1;
      flag_gcse_after_reload = 1;
    }

  if (optimize < 2 || optimize_size)
    {
      align_loops = 1;
      align_jumps = 1;
      align_labels = 1;
      align_functions = 1;

      /* Don't reorder blocks when optimizing for size because extra
	 jump insns may be created; also barrier may create extra padding.

	 More correctly we should have a block reordering mode that tried
	 to minimize the combined size of all the jumps.  This would more
	 or less automatically remove extra jumps, but would also try to
	 use more short jumps instead of long jumps.  */
      flag_reorder_blocks = 0;
      flag_reorder_blocks_and_partition = 0;
    }

  if (optimize_size)
    {
      /* Inlining of very small functions usually reduces total size.  */
      set_param_value ("max-inline-insns-single", 5);
      set_param_value ("max-inline-insns-auto", 5);
      set_param_value ("max-inline-insns-rtl", 10);
      flag_inline_functions = 1;
    }

(note this is from 3.5-tree-ssa 20040504 (merged 20040428))

-- 
		Serge