Where can I get the output of the front-end.

Where can I get the output of the front-end.

[Matthieu Moy]

Hi,

I'm  still trying  to re-use  the  front-end of  GCC to  do some  code
analysis. (I'm using the tree-ssa branch)

I begin  to understand how the  data structures are made,  but I don't
understand *where*, in the programm, they are generated. 

What I would like to do is

C++ source -----> SSA tree ---(standard way)----> RTL
                             \
                              `---(my add-on)---> ...

So, I thought of  hacking the ssa -> rtl code, but  I can't find which
function is doing so in gcc ! 

Any help appreciated, thanks,

-- 
Matthieu

Re: Where can I get the output of the front-end.

[Steven Bosscher]

Op do 03-04-2003, om 18:09 schreef Matthieu Moy:
> Hi,
> 
> I'm  still trying  to re-use  the  front-end of  GCC to  do some  code
> analysis. (I'm using the tree-ssa branch)
> 
> I begin  to understand how the  data structures are made,  but I don't
> understand *where*, in the programm, they are generated. 
> 
> What I would like to do is
> 
> C++ source -----> SSA tree ---(standard way)----> RTL
>                              \
>                               `---(my add-on)---> ...
> 
> So, I thought of  hacking the ssa -> rtl code, but  I can't find which
> function is doing so in gcc ! 
> 
> Any help appreciated, thanks,

Look at tree-optimize.c, or if you want to hook in after the SSA
optimizers are done, grep for TV_EXPAND in c-decl.c.

Greetz
Steven

Re: Where can I get the output of the front-end.

[Pop Sébastian]

On Thu, Apr 03, 2003 at 06:09:35PM +0200, Matthieu Moy wrote:
> What I would like to do is
> 
> C++ source -----> SSA tree ---(standard way)----> RTL
>                              \
>                               `---(my add-on)---> ...
> 
> So, I thought of  hacking the ssa -> rtl code, but  I can't find which
> function is doing so in gcc ! 
> 

The rtl is generated by the "emit_*" functions from expr.c
and "genrtl_*" functions from stmt.c

http://gcc.gnu.org/ml/gcc/2002-09/msg01051.html

But I think that what you're looking for is tree-optimize.c where 
you have the tree in the SSA representation: 


  /* Build the flowgraph.  */
  init_flow ();
  build_tree_cfg (fnbody);

  /* Begin analysis and optimization passes.  */
  if (n_basic_blocks > 0 && ! (errorcount || sorrycount))
    {
      /* Rewrite the function into SSA form.  */
      rewrite_into_ssa (fndecl);
      
      if (flag_tree_pre)
	tree_perform_ssapre (fndecl);

      if (flag_tree_ccp)
	tree_ssa_ccp (fndecl);
      
      if (flag_tree_copyprop)
	tree_ssa_copyprop (fndecl);

      if (flag_tree_dce)
	tree_ssa_dce (fndecl);
    }

  if (n_basic_blocks > 0 && ! (errorcount || sorrycount))
    {
      /* Rewrite the function out of SSA form.  */
      rewrite_out_of_ssa (fndecl);
    }


This code is reachable if you compile with -O2.

Re: Where can I get the output of the front-end.

[Matthieu Moy]

Steven Bosscher <s.bosscher@student.tudelft.nl> writes:

> Op do 03-04-2003, om 18:09 schreef Matthieu Moy:
>> Hi,
>> 
>> I'm  still trying  to re-use  the  front-end of  GCC to  do some  code
>> analysis. (I'm using the tree-ssa branch)

[...]

> Look at  tree-optimize.c, or if  you want to  hook in after  the SSA

OK, I could do it. 

I still have 2 questions :

* I  plugged myself  just  after  the ssa  optimizations  by adding  a
  function  call.  What  I  don't  manage  to  do  is  to  remove  the
  backend ... (My modified code still generates RTL and assembler)

* I can see the functions one by one, but is there a moment during the
  compilation  at which we  can see  the whole  program in  one single
  tree ? (A kind of list of functions and declarations)

Thanks,

-- 
Matthieu

Re: Where can I get the output of the front-end.

[Pop Sébastian]

> * I can see the functions one by one, but is there a moment during the
>   compilation  at which we  can see  the whole  program in  one single
>   tree ? (A kind of list of functions and declarations)
> 

From cgraphunit.c:

/* Analyze the whole compilation unit once it is parsed completely.  */

void
cgraph_finalize_compilation_unit ()


>  
> * I  plugged myself  just  after  the ssa  optimizations  by adding  a 
>   function  call.  What  I  don't  manage  to  do  is  to  remove  the 
>   backend ... (My modified code still generates RTL and assembler) 
>  

Define a global variable, say "rest_of_compilation_needed", that will
control the access to the back_end:

Index: c-decl.c
===================================================================
RCS file: /home/pop/cvsroot/gcc-cvs/gcc/gcc/c-decl.c,v
retrieving revision 1.334.2.41
diff -u -3 -p -c -r1.334.2.41 c-decl.c
*** c-decl.c	13 Mar 2003 22:24:24 -0000	1.334.2.41
--- c-decl.c	4 Apr 2003 18:50:04 -0000
*************** c_expand_body_1 (fndecl, nested_p)
*** 6630,6637 ****
    input_filename = saved_input_filename;
    lineno = saved_lineno;
  
!   /* Run the optimizers and output the assembler code for this function.  */
!   rest_of_compilation (fndecl);
  
    /* Undo the GC context switch.  */
    if (nested_p)
--- 6630,6638 ----
    input_filename = saved_input_filename;
    lineno = saved_lineno;
  
!   if (rest_of_compilation_needed)
!     /* Run the optimizers and output the assembler code for this function.  */
!     rest_of_compilation (fndecl);
  
    /* Undo the GC context switch.  */
    if (nested_p)