Dominance information problem

[Gary Oblock]

Erick,

I assume that this needs to be done on all the functions since
you mention "cfun".

Gary
________________________________
From: Erick Ochoa <erick.ochoa@theobroma-systems.com>
Sent: Monday, September 14, 2020 12:10 AM
To: Gary Oblock <gary@amperecomputing.com>; gcc@gcc.gnu.org <gcc@gcc.gnu.org>
Subject: Re: Dominance information problem

[EXTERNAL EMAIL NOTICE: This email originated from an external sender. Please be mindful of safe email handling and proprietary information protection practices.]


Hi Gary,

I'm not 100% sure this will fix the problem, but in the past I have had
to call the following function:

   /* If dominator info is not available, we need to calculate it.  */
   if (!dom_info_available_p (CDI_DOMINATORS))
     calculate_dominance_info (CDI_DOMINATORS);

Basically dominance information was not available for cfun.
Also, you might also need to call:

   if (dom_info_available_p (CDI_DOMINATORS))
     free_dominance_info (CDI_DOMINATORS);

Just before your pass is done. These were some calls I needed to make in
a different pass when I was working with dominators.

On 12/09/2020 09:26, Gary Oblock wrote:
> I'm trying to do performance qualification for my structure
> reorganization optimization.
>
> I'm doing pretty straightforward stuff and I haven't at this point in
> time (qualifying the optimization,) modified the program. So I'm a
> little surprised this is failing.  Here is the code that's failing on
> the first iteration of the for loops:
>
>    struct cgraph_node *node;
>    FOR_EACH_FUNCTION_WITH_GIMPLE_BODY ( node)  {
>      struct function *func = DECL_STRUCT_FUNCTION ( node->decl);
>      push_cfun ( func);
>
>      class loop *loop;
>      FOR_EACH_LOOP_FN ( func, loop, LI_ONLY_INNERMOST )
>        {
>          size_t num_bbs = loop->num_nodes;
>          basic_block *bbs = get_loop_body ( loop); // FAILS HERE!!!
>          :
>          stuff never reached
>
> How it's failing (in code from dominance.c) I'm guessing tells me the
> dominance information is messed up (unlikely) or needs to be
> recomputed. If I'm not wrong, how do I go about doing the later????
>
> /* Return TRUE in case BB1 is dominated by BB2.  */
> bool
> dominated_by_p (enum cdi_direction dir, const_basic_block bb1, const_basic_block bb2)
> {
>    unsigned int dir_index = dom_convert_dir_to_idx (dir);
>    struct et_node *n1 = bb1->dom[dir_index], *n2 = bb2->dom[dir_index];
>
>    gcc_checking_assert (dom_computed[dir_index]); // <=========== BOOM!
>
>    if (dom_computed[dir_index] == DOM_OK)
>      return (n1->dfs_num_in >= n2->dfs_num_in
>       && n1->dfs_num_out <= n2->dfs_num_out);
>
>    return et_below (n1, n2);
> }
>
>
> Thanks,
>
> Gary Oblock
>
>
>
>
>
>
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