gcc源代码分析，debug_rtx()函数，利器啊

print-tree.c

#include "config.h"

#include "tree.h"

#include <stdio.h>

/* Names of tree components.

Used for printing out the tree and error messages.  */

#define DEFTREECODE(SYM, NAME, TYPE, LEN) NAME,

char *tree_code_name[] = {

#include "tree.def"

};

#undef DEFTREECODE

同样的debug_tree()函数放在哪里才有用是个重要而有用的问题，

只有看完相关的代码才能知道。

我认为放到expr.c文件中比较好。

if (mode != Pmode && modifier == EXPAND_SUM)

modifier = EXPAND_NORMAL;

fprintf(stderr ,"expand_expr code = %x\n",code);

debug_tree (exp);

/* Ensure we reference a volatile object even if value is ignored.  */

if (ignore && TREE_THIS_VOLATILE (exp)

&& mode != VOIDmode && mode != BLKmode)

{

target = gen_reg_rtx (mode);

temp = expand_expr (exp, target, VOIDmode, modifier);

if (temp != target)

emit_move_insn (target, temp);

return target;

}

switch (code)
/*再这个关键的分支处，之前打印出语法树是个明智的选择*/

{

case PARM_DECL:

if (DECL_RTL (exp) == 0)

{

error_with_decl (exp, "prior parameter‘s size depends on `%s‘");

return const0_rtx;

}

case FUNCTION_DECL:

case VAR_DECL: