adding nodes in a tree --after GIMPLIFICATION, before SSA

["sean yang" <seanatpurdue at hotmail dot com>]

I will appreciate your help. Thanks in advance.

Let me give a concrete example of what I want to do (Please understand I 
have other reasons to do this after gimplification, though the example shows 
that there is a much simpler way to achieve this):  in the example, I want 
to add a call of instrument() after each call of foo()
-----------------------
//input source: example.c
main(){
  int i=0;
  foo();
  i++;
  bar();
}
-----------------------------
//conceptual source: with my compiler, the output should look like the 
output of the following source code
main(){
  int i=0;
  foo();
  instrument(); //i.e, adding a node of CALL_EXPR (instrument) after each 
node CALL_EXPR (foo)
  i++;
  bar();
}
-----------------------------

What I want to do is whenever I find a CALL_EXPR node, I look up its ID to 
see if it is "foo". If it is, I add another CALL_EXPR node with ID of 
"instrument". I have two questions:
(1) I know "call_node = build (CALL_EXPR, tree_node)" can build a new node, 
but how can I fill the field of tree_node properly? i.e., make the content 
of tree_node be a call to "instrument". It seems there is no API to do so.

(2) after the node the call_node has been built, how can I added to the 
proper place? It seems that tsi_link_after () can't do what I want under 
this situation because it's only used for STATEMENT_LIST, not other type of 
nodes, like CALL_EXPR.

Can someone give me some help or hint on above two questions?

//pass-myinstrument.c
static void
add_instruments (tree *tp)
{
 tree t=*tp, op, new_call;

 switch (TREE_CODE (t))
   {
   case CALL_EXPR:
     //I want to add another CALL_EXPR node after the current CALL_EXPR 
node
     //*******this is my question ***********
     break;
   case COND_EXPR:
     add_instruments ( &COND_EXPR_THEN(t));
     add_instruments ( &COND_EXPR_ELSE(t));
     break;
   case BIND_EXPR:
     add_instruments ( &BIND_EXPR_BODY(t));
     break;
   //and other cases not shown here
   default:
     fprintf(stderr, "%d\n", TREE_CODE(t));
     break;
   }
}

static void
code_instrumentation (void)
{
  add_instruments (&DECL_SAVED_TREE (current_function_decl));
}

struct tree_opt_pass pass_beacon_instrument =
{
 "my_instrumentation",				/* name */
 NULL,					/* gate */
 code_instrumentation,				/* execute */
 NULL,					/* sub */
 NULL,					/* next */
 0,					/* static_pass_number */
 TV_TREE_BEACON_INSERTION,				/* tv_id */
 0,				/* properties_required */
 0,					/* properties_provided */
 0,					/* properties_destroyed */
 0,					/* todo_flags_start */
 TODO_dump_func | TODO_ggc_collect,			/* todo_flags_finish */
 0					/* letter */
};


The place of the added pass is shown here
---------------------------------------------------------
//file name: tree-optimize.c GCC4.0.2
   init_tree_optimization_passes (void)
   {
     struct tree_opt_pass **p;
     #define NEXT_PASS(PASS)  (p = next_pass_1 (p, &PASS))
     p = &all_passes;
     NEXT_PASS (pass_gimple);

     // this is where the pass is added
     NEXT_PASS (pass_beacon_instrument);

     NEXT_PASS (pass_remove_useless_stmts);
     //....
    }
-------------------------------------------------------------------

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