Free more of CFG in release_function_body

[Richard Biener]

On Tue, 24 Nov 2020, Jan Hubicka wrote:

> Hi,
> at the end of processing function body we loop over basic blocks and
> free all edges while we do not free the rest.  I think this is leftover
> from time eges was not garbage collected and we was not using ggc_free.
> It makes more sense to free all associated structures (which is
> importnat for WPA memory footprint).
> 
> Bootstrapped/regtested x86_64-linux, OK?

OK.

> Honza
> 
> 	* cfg.c (free_block): New function.
> 	(clear_edges): Rename to ....
> 	(free_cfg): ... this one; also free BBs and vectors.
> 	(expunge_block): Update comment.
> 	* cfg.h (clear_edges): Rename to ...
> 	(free_cfg): ... this one.
> 	* cgraph.c (release_function_body): Use free_cfg.
> diff --git a/gcc/cfg.c b/gcc/cfg.c
> index de0e71db850..fc78e48d6e1 100644
> --- a/gcc/cfg.c
> +++ b/gcc/cfg.c
> @@ -25,7 +25,7 @@ along with GCC; see the file COPYING3.  If not see
>  
>     Available functionality:
>       - Initialization/deallocation
> -	 init_flow, clear_edges
> +	 init_flow, free_cfg
>       - Low level basic block manipulation
>  	 alloc_block, expunge_block
>       - Edge manipulation
> @@ -83,7 +83,7 @@ init_flow (struct function *the_fun)
>    the_fun->cfg->bb_flags_allocated = BB_ALL_FLAGS;
>  }
>  
> -/* Helper function for remove_edge and clear_edges.  Frees edge structure
> +/* Helper function for remove_edge and free_cffg.  Frees edge structure
>     without actually removing it from the pred/succ arrays.  */
>  
>  static void
> @@ -93,29 +93,41 @@ free_edge (function *fn, edge e)
>    ggc_free (e);
>  }
>  
> -/* Free the memory associated with the edge structures.  */
> +/* Free basic block BB.  */
> +
> +static void
> +free_block (basic_block bb)
> +{
> +   vec_free (bb->succs);
> +   vec_free (bb->preds);
> +   ggc_free (bb);
> +}
> +
> +/* Free the memory associated with the CFG in FN.  */
>  
>  void
> -clear_edges (struct function *fn)
> +free_cfg (struct function *fn)
>  {
> -  basic_block bb;
>    edge e;
>    edge_iterator ei;
> +  basic_block next;
>  
> -  FOR_EACH_BB_FN (bb, fn)
> +  for (basic_block bb = ENTRY_BLOCK_PTR_FOR_FN (fn); bb; bb = next)
>      {
> +      next = bb->next_bb;
>        FOR_EACH_EDGE (e, ei, bb->succs)
>  	free_edge (fn, e);
> -      vec_safe_truncate (bb->succs, 0);
> -      vec_safe_truncate (bb->preds, 0);
> +      free_block (bb);
>      }
>  
> -  FOR_EACH_EDGE (e, ei, ENTRY_BLOCK_PTR_FOR_FN (fn)->succs)
> -    free_edge (fn, e);
> -  vec_safe_truncate (EXIT_BLOCK_PTR_FOR_FN (fn)->preds, 0);
> -  vec_safe_truncate (ENTRY_BLOCK_PTR_FOR_FN (fn)->succs, 0);
> -
>    gcc_assert (!n_edges_for_fn (fn));
> +  /* Sanity check that dominance tree is freed.  */
> +  gcc_assert (!fn->cfg->x_dom_computed[0] && !fn->cfg->x_dom_computed[1]);
> +  
> +  vec_free (fn->cfg->x_label_to_block_map);
> +  vec_free (basic_block_info_for_fn (fn));
> +  ggc_free (fn->cfg);
> +  fn->cfg = NULL;
>  }
>  
>  /* Allocate memory for basic_block.  */
> @@ -190,8 +202,8 @@ expunge_block (basic_block b)
>    /* We should be able to ggc_free here, but we are not.
>       The dead SSA_NAMES are left pointing to dead statements that are pointing
>       to dead basic blocks making garbage collector to die.
> -     We should be able to release all dead SSA_NAMES and at the same time we should
> -     clear out BB pointer of dead statements consistently.  */
> +     We should be able to release all dead SSA_NAMES and at the same time we
> +     should clear out BB pointer of dead statements consistently.  */
>  }
>  
>  /* Connect E to E->src.  */
> diff --git a/gcc/cfg.h b/gcc/cfg.h
> index 93fde6df2bf..a9c8300f173 100644
> --- a/gcc/cfg.h
> +++ b/gcc/cfg.h
> @@ -82,7 +82,7 @@ struct GTY(()) control_flow_graph {
>  
>  
>  extern void init_flow (function *);
> -extern void clear_edges (function *);
> +extern void free_cfg (function *);
>  extern basic_block alloc_block (void);
>  extern void link_block (basic_block, basic_block);
>  extern void unlink_block (basic_block);
> diff --git a/gcc/cgraph.c b/gcc/cgraph.c
> index 19dfe2be23b..5c48a1bb92b 100644
> --- a/gcc/cgraph.c
> +++ b/gcc/cgraph.c
> @@ -1811,7 +1811,7 @@ release_function_body (tree decl)
>  	  gcc_assert (!dom_info_available_p (fn, CDI_DOMINATORS));
>  	  gcc_assert (!dom_info_available_p (fn, CDI_POST_DOMINATORS));
>  	  delete_tree_cfg_annotations (fn);
> -	  clear_edges (fn);
> +	  free_cfg (fn);
>  	  fn->cfg = NULL;
>  	}
>        if (fn->value_histograms)
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Felix Imend