本文主要是分析store_one_arg ()函数和expand_expr ()的关系来说明如何处理

函数的参数。printf("Hello, world!\n");中的"Hello, world!\n"这个字符串常量的！

expand_call () 函数中的相关代码：

      if (args[i].reg == 0
      && TYPE_SIZE (TREE_TYPE (args[i].tree_value)) != 0)
    {
    fprintf(stderr,"before store_one_arg \n");
    store_one_arg (&args[i], argblock, may_be_alloca);
    fprintf(stderr,"after store_one_arg \n ");
    }

下面是 store_one_arg ()函数中的相关代码：

static void
store_one_arg (arg, argblock, may_be_alloca)
     struct arg_data *arg;
     rtx argblock;
     int may_be_alloca;
{
  register tree pval = arg->tree_value;
  int used = 0;

  if (TREE_CODE (pval) == ERROR_MARK)
    return;
fprintf(stderr,"in store_one_arg debug_tree pval \n");
   debug_tree(pval); 
...

  else if (TYPE_MODE (TREE_TYPE (pval)) != BLKmode)
    {
      register int size;
      rtx tem;

      fprintf(stderr,"else if type_mode 1 \n");
      /* Argument is a scalar, not entirely passed in registers.
     (If part is passed in registers, arg->partial says how much
     and emit_push_insn will take care of putting it there.)
    
     Push it, and if its size is less than the
     amount of space allocated to it,
     also bump stack pointer by the additional space.
     Note that in C the default argument promotions
     will prevent such mismatches.  */

      size = GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (pval)));
      /* Compute how much space the push instruction will push.
     On many machines, pushing a byte will advance the stack
     pointer by a halfword.  */
#ifdef PUSH_ROUNDING
      size = PUSH_ROUNDING (size);
#endif
      used = size;

      /* Compute how much space the argument should get:
     round up to a multiple of the alignment for arguments.  */
      if (none != FUNCTION_ARG_PADDING (TYPE_MODE (TREE_TYPE (pval)), const0_rtx))
    used = (((size + PARM_BOUNDARY / BITS_PER_UNIT - 1)
         / (PARM_BOUNDARY / BITS_PER_UNIT))
        * (PARM_BOUNDARY / BITS_PER_UNIT));

      tem = arg->value;
      if (tem == 0)
    {
     fprintf(stderr,"else if type_mode 2\n");
       tem = expand_expr (pval, 0, VOIDmode, 0);
      /* ANSI doesn‘t require a sequence point here,
         but PCC has one, so this will avoid some problems.  */
     fprintf(stderr,"else if type_mode 3\n");
      emit_queue ();
    }

      /* Don‘t allow anything left on stack from computation
     of argument to alloca.  */
      if (may_be_alloca)
    do_pending_stack_adjust ();

      fprintf(stderr,"else if type_mode 4 \n");
      emit_push_insn (tem, TYPE_MODE (TREE_TYPE (pval)), 0, 0,
              arg->partial, arg->reg, used - size,
              argblock, ARGS_SIZE_RTX (arg->offset));
    }

下面是调试结果：

before store_one_arg

gcc源代码分析，expand_call ()函数分析第五部分，store_one_arg ()函数