gcc/gcc/ipa-utils.c

/* Utilities for ipa analysis.
   Copyright (C) 2005-2018 Free Software Foundation, Inc.
   Contributed by Kenneth Zadeck <zadeck@naturalbridge.com>

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "backend.h"
#include "tree.h"
#include "gimple.h"
#include "predict.h"
#include "alloc-pool.h"
#include "cgraph.h"
#include "lto-streamer.h"
#include "dumpfile.h"
#include "splay-tree.h"
#include "ipa-utils.h"
#include "symbol-summary.h"
#include "tree-vrp.h"
#include "ipa-prop.h"
#include "ipa-fnsummary.h"

/* Debugging function for postorder and inorder code. NOTE is a string
   that is printed before the nodes are printed.  ORDER is an array of
   cgraph_nodes that has COUNT useful nodes in it.  */

void
ipa_print_order (FILE* out,
		 const char * note,
		 struct cgraph_node** order,
		 int count)
{
  int i;
  fprintf (out, "\n\n ordered call graph: %s\n", note);

  for (i = count - 1; i >= 0; i--)
    order[i]->dump (out);
  fprintf (out, "\n");
  fflush (out);
}


struct searchc_env {
  struct cgraph_node **stack;
  struct cgraph_node **result;
  int stack_size;
  int order_pos;
  splay_tree nodes_marked_new;
  bool reduce;
  bool allow_overwritable;
  int count;
};

/* This is an implementation of Tarjan's strongly connected region
   finder as reprinted in Aho Hopcraft and Ullman's The Design and
   Analysis of Computer Programs (1975) pages 192-193.  This version
   has been customized for cgraph_nodes.  The env parameter is because
   it is recursive and there are no nested functions here.  This
   function should only be called from itself or
   ipa_reduced_postorder.  ENV is a stack env and would be
   unnecessary if C had nested functions.  V is the node to start
   searching from.  */

static void
searchc (struct searchc_env* env, struct cgraph_node *v,
	 bool (*ignore_edge) (struct cgraph_edge *))
{
  struct cgraph_edge *edge;
  struct ipa_dfs_info *v_info = (struct ipa_dfs_info *) v->aux;

  /* mark node as old */
  v_info->new_node = false;
  splay_tree_remove (env->nodes_marked_new, v->uid);

  v_info->dfn_number = env->count;
  v_info->low_link = env->count;
  env->count++;
  env->stack[(env->stack_size)++] = v;
  v_info->on_stack = true;

  for (edge = v->callees; edge; edge = edge->next_callee)
    {
      struct ipa_dfs_info * w_info;
      enum availability avail;
      struct cgraph_node *w = edge->callee->ultimate_alias_target (&avail);

      if (!w || (ignore_edge && ignore_edge (edge)))
        continue;

      if (w->aux
	  && (avail > AVAIL_INTERPOSABLE
	      || (env->allow_overwritable && avail == AVAIL_INTERPOSABLE)))
	{
	  w_info = (struct ipa_dfs_info *) w->aux;
	  if (w_info->new_node)
	    {
	      searchc (env, w, ignore_edge);
	      v_info->low_link =
		(v_info->low_link < w_info->low_link) ?
		v_info->low_link : w_info->low_link;
	    }
	  else
	    if ((w_info->dfn_number < v_info->dfn_number)
		&& (w_info->on_stack))
	      v_info->low_link =
		(w_info->dfn_number < v_info->low_link) ?
		w_info->dfn_number : v_info->low_link;
	}
    }


  if (v_info->low_link == v_info->dfn_number)
    {
      struct cgraph_node *last = NULL;
      struct cgraph_node *x;
      struct ipa_dfs_info *x_info;
      do {
	x = env->stack[--(env->stack_size)];
	x_info = (struct ipa_dfs_info *) x->aux;
	x_info->on_stack = false;
	x_info->scc_no = v_info->dfn_number;

	if (env->reduce)
	  {
	    x_info->next_cycle = last;
	    last = x;
	  }
	else
	  env->result[env->order_pos++] = x;
      }
      while (v != x);
      if (env->reduce)
	env->result[env->order_pos++] = v;
    }
}

/* Topsort the call graph by caller relation.  Put the result in ORDER.

   The REDUCE flag is true if you want the cycles reduced to single nodes.
   You can use ipa_get_nodes_in_cycle to obtain a vector containing all real
   call graph nodes in a reduced node.

   Set ALLOW_OVERWRITABLE if nodes with such availability should be included.
   IGNORE_EDGE, if non-NULL is a hook that may make some edges insignificant
   for the topological sort.   */

int
ipa_reduced_postorder (struct cgraph_node **order,
		       bool reduce, bool allow_overwritable,
		       bool (*ignore_edge) (struct cgraph_edge *))
{
  struct cgraph_node *node;
  struct searchc_env env;
  splay_tree_node result;
  env.stack = XCNEWVEC (struct cgraph_node *, symtab->cgraph_count);
  env.stack_size = 0;
  env.result = order;
  env.order_pos = 0;
  env.nodes_marked_new = splay_tree_new (splay_tree_compare_ints, 0, 0);
  env.count = 1;
  env.reduce = reduce;
  env.allow_overwritable = allow_overwritable;

  FOR_EACH_DEFINED_FUNCTION (node)
    {
      enum availability avail = node->get_availability ();

      if (avail > AVAIL_INTERPOSABLE
	  || (allow_overwritable
	      && (avail == AVAIL_INTERPOSABLE)))
	{
	  /* Reuse the info if it is already there.  */
	  struct ipa_dfs_info *info = (struct ipa_dfs_info *) node->aux;
	  if (!info)
	    info = XCNEW (struct ipa_dfs_info);
	  info->new_node = true;
	  info->on_stack = false;
	  info->next_cycle = NULL;
	  node->aux = info;

	  splay_tree_insert (env.nodes_marked_new,
			     (splay_tree_key)node->uid,
			     (splay_tree_value)node);
	}
      else
	node->aux = NULL;
    }
  result = splay_tree_min (env.nodes_marked_new);
  while (result)
    {
      node = (struct cgraph_node *)result->value;
      searchc (&env, node, ignore_edge);
      result = splay_tree_min (env.nodes_marked_new);
    }
  splay_tree_delete (env.nodes_marked_new);
  free (env.stack);

  return env.order_pos;
}

/* Deallocate all ipa_dfs_info structures pointed to by the aux pointer of call
   graph nodes.  */

void
ipa_free_postorder_info (void)
{
  struct cgraph_node *node;
  FOR_EACH_DEFINED_FUNCTION (node)
    {
      /* Get rid of the aux information.  */
      if (node->aux)
	{
	  free (node->aux);
	  node->aux = NULL;
	}
    }
}

/* Get the set of nodes for the cycle in the reduced call graph starting
   from NODE.  */

vec<cgraph_node *>
ipa_get_nodes_in_cycle (struct cgraph_node *node)
{
  vec<cgraph_node *> v = vNULL;
  struct ipa_dfs_info *node_dfs_info;
  while (node)
    {
      v.safe_push (node);
      node_dfs_info = (struct ipa_dfs_info *) node->aux;
      node = node_dfs_info->next_cycle;
    }
  return v;
}

/* Return true iff the CS is an edge within a strongly connected component as
   computed by ipa_reduced_postorder.  */

bool
ipa_edge_within_scc (struct cgraph_edge *cs)
{
  struct ipa_dfs_info *caller_dfs = (struct ipa_dfs_info *) cs->caller->aux;
  struct ipa_dfs_info *callee_dfs;
  struct cgraph_node *callee = cs->callee->function_symbol ();

  callee_dfs = (struct ipa_dfs_info *) callee->aux;
  return (caller_dfs
	  && callee_dfs
	  && caller_dfs->scc_no == callee_dfs->scc_no);
}

struct postorder_stack
{
  struct cgraph_node *node;
  struct cgraph_edge *edge;
  int ref;
};

/* Fill array order with all nodes with output flag set in the reverse
   topological order.  Return the number of elements in the array.
   FIXME: While walking, consider aliases, too.  */

int
ipa_reverse_postorder (struct cgraph_node **order)
{
  struct cgraph_node *node, *node2;
  int stack_size = 0;
  int order_pos = 0;
  struct cgraph_edge *edge;
  int pass;
  struct ipa_ref *ref = NULL;

  struct postorder_stack *stack =
    XCNEWVEC (struct postorder_stack, symtab->cgraph_count);

  /* We have to deal with cycles nicely, so use a depth first traversal
     output algorithm.  Ignore the fact that some functions won't need
     to be output and put them into order as well, so we get dependencies
     right through inline functions.  */
  FOR_EACH_FUNCTION (node)
    node->aux = NULL;
  for (pass = 0; pass < 2; pass++)
    FOR_EACH_FUNCTION (node)
      if (!node->aux
	  && (pass
	      || (!node->address_taken
		  && !node->global.inlined_to
		  && !node->alias && !node->thunk.thunk_p
		  && !node->only_called_directly_p ())))
	{
	  stack_size = 0;
          stack[stack_size].node = node;
	  stack[stack_size].edge = node->callers;
	  stack[stack_size].ref = 0;
	  node->aux = (void *)(size_t)1;
	  while (stack_size >= 0)
	    {
	      while (true)
		{
		  node2 = NULL;
		  while (stack[stack_size].edge && !node2)
		    {
		      edge = stack[stack_size].edge;
		      node2 = edge->caller;
		      stack[stack_size].edge = edge->next_caller;
		      /* Break possible cycles involving always-inline
			 functions by ignoring edges from always-inline
			 functions to non-always-inline functions.  */
		      if (DECL_DISREGARD_INLINE_LIMITS (edge->caller->decl)
			  && !DECL_DISREGARD_INLINE_LIMITS
			    (edge->callee->function_symbol ()->decl))
			node2 = NULL;
		    }
		  for (; stack[stack_size].node->iterate_referring (
						       stack[stack_size].ref,
						       ref) && !node2;
		       stack[stack_size].ref++)
		    {
		      if (ref->use == IPA_REF_ALIAS)
			node2 = dyn_cast <cgraph_node *> (ref->referring);
		    }
		  if (!node2)
		    break;
		  if (!node2->aux)
		    {
		      stack[++stack_size].node = node2;
		      stack[stack_size].edge = node2->callers;
		      stack[stack_size].ref = 0;
		      node2->aux = (void *)(size_t)1;
		    }
		}
	      order[order_pos++] = stack[stack_size--].node;
	    }
	}
  free (stack);
  FOR_EACH_FUNCTION (node)
    node->aux = NULL;
  return order_pos;
}



/* Given a memory reference T, will return the variable at the bottom
   of the access.  Unlike get_base_address, this will recurse through
   INDIRECT_REFS.  */

tree
get_base_var (tree t)
{
  while (!SSA_VAR_P (t)
	 && (!CONSTANT_CLASS_P (t))
	 && TREE_CODE (t) != LABEL_DECL
	 && TREE_CODE (t) != FUNCTION_DECL
	 && TREE_CODE (t) != CONST_DECL
	 && TREE_CODE (t) != CONSTRUCTOR)
    {
      t = TREE_OPERAND (t, 0);
    }
  return t;
}


/* SRC and DST are going to be merged.  Take SRC's profile and merge it into
   DST so it is not going to be lost.  Possibly destroy SRC's body on the way
   unless PRESERVE_BODY is set.  */

void
ipa_merge_profiles (struct cgraph_node *dst,
		    struct cgraph_node *src,
		    bool preserve_body)
{
  tree oldsrcdecl = src->decl;
  struct function *srccfun, *dstcfun;
  bool match = true;

  if (!src->definition
      || !dst->definition)
    return;
  if (src->frequency < dst->frequency)
    src->frequency = dst->frequency;

  /* Time profiles are merged.  */
  if (dst->tp_first_run > src->tp_first_run && src->tp_first_run)
    dst->tp_first_run = src->tp_first_run;

  if (src->profile_id && !dst->profile_id)
    dst->profile_id = src->profile_id;

  /* FIXME when we merge in unknown profile, we ought to set counts as
     unsafe.  */
  if (!src->count.initialized_p ()
      || !(src->count.ipa () == src->count))
    return;
  if (symtab->dump_file)
    {
      fprintf (symtab->dump_file, "Merging profiles of %s to %s\n",
	       src->dump_name (), dst->dump_name ());
    }
  if (dst->count.initialized_p () && dst->count.ipa () == dst->count)
    dst->count += src->count.ipa ();
  else 
    dst->count = src->count.ipa ();

  /* This is ugly.  We need to get both function bodies into memory.
     If declaration is merged, we need to duplicate it to be able
     to load body that is being replaced.  This makes symbol table
     temporarily inconsistent.  */
  if (src->decl == dst->decl)
    {
      struct lto_in_decl_state temp;
      struct lto_in_decl_state *state;

      /* We are going to move the decl, we want to remove its file decl data.
	 and link these with the new decl. */
      temp.fn_decl = src->decl;
      lto_in_decl_state **slot
	= src->lto_file_data->function_decl_states->find_slot (&temp,
							       NO_INSERT);
      state = *slot;
      src->lto_file_data->function_decl_states->clear_slot (slot);
      gcc_assert (state);

      /* Duplicate the decl and be sure it does not link into body of DST.  */
      src->decl = copy_node (src->decl);
      DECL_STRUCT_FUNCTION (src->decl) = NULL;
      DECL_ARGUMENTS (src->decl) = NULL;
      DECL_INITIAL (src->decl) = NULL;
      DECL_RESULT (src->decl) = NULL;

      /* Associate the decl state with new declaration, so LTO streamer
 	 can look it up.  */
      state->fn_decl = src->decl;
      slot
	= src->lto_file_data->function_decl_states->find_slot (state, INSERT);
      gcc_assert (!*slot);
      *slot = state;
    }
  src->get_untransformed_body ();
  dst->get_untransformed_body ();
  srccfun = DECL_STRUCT_FUNCTION (src->decl);
  dstcfun = DECL_STRUCT_FUNCTION (dst->decl);
  if (n_basic_blocks_for_fn (srccfun)
      != n_basic_blocks_for_fn (dstcfun))
    {
      if (symtab->dump_file)
	fprintf (symtab->dump_file,
		 "Giving up; number of basic block mismatch.\n");
      match = false;
    }
  else if (last_basic_block_for_fn (srccfun)
	   != last_basic_block_for_fn (dstcfun))
    {
      if (symtab->dump_file)
	fprintf (symtab->dump_file,
		 "Giving up; last block mismatch.\n");
      match = false;
    }
  else 
    {
      basic_block srcbb, dstbb;

      FOR_ALL_BB_FN (srcbb, srccfun)
	{
	  unsigned int i;

	  dstbb = BASIC_BLOCK_FOR_FN (dstcfun, srcbb->index);
	  if (dstbb == NULL)
	    {
	      if (symtab->dump_file)
		fprintf (symtab->dump_file,
			 "No matching block for bb %i.\n",
			 srcbb->index);
	      match = false;
	      break;
	    }
	  if (EDGE_COUNT (srcbb->succs) != EDGE_COUNT (dstbb->succs))
	    {
	      if (symtab->dump_file)
		fprintf (symtab->dump_file,
			 "Edge count mistmatch for bb %i.\n",
			 srcbb->index);
	      match = false;
	      break;
	    }
	  for (i = 0; i < EDGE_COUNT (srcbb->succs); i++)
	    {
	      edge srce = EDGE_SUCC (srcbb, i);
	      edge dste = EDGE_SUCC (dstbb, i);
	      if (srce->dest->index != dste->dest->index)
		{
		  if (symtab->dump_file)
		    fprintf (symtab->dump_file,
			     "Succ edge mistmatch for bb %i.\n",
			     srce->dest->index);
		  match = false;
		  break;
		}
	    }
	}
    }
  if (match)
    {
      struct cgraph_edge *e, *e2;
      basic_block srcbb, dstbb;

      /* TODO: merge also statement histograms.  */
      FOR_ALL_BB_FN (srcbb, srccfun)
	{
	  unsigned int i;

	  dstbb = BASIC_BLOCK_FOR_FN (dstcfun, srcbb->index);

	  /* Either sum the profiles if both are IPA and not global0, or
	     pick more informative one (that is nonzero IPA if other is
	     uninitialized, guessed or global0).   */
	  if (!dstbb->count.ipa ().initialized_p ()
	      || (dstbb->count.ipa () == profile_count::zero ()
		  && (srcbb->count.ipa ().initialized_p ()
		      && !(srcbb->count.ipa () == profile_count::zero ()))))
	    {
	      dstbb->count = srcbb->count;
	      for (i = 0; i < EDGE_COUNT (srcbb->succs); i++)
		{
		  edge srce = EDGE_SUCC (srcbb, i);
		  edge dste = EDGE_SUCC (dstbb, i);
		  if (srce->probability.initialized_p ())
		    dste->probability = srce->probability;
		}
	    }	
	  else if (srcbb->count.ipa ().initialized_p ()
		   && !(srcbb->count.ipa () == profile_count::zero ()))
	    {
	      for (i = 0; i < EDGE_COUNT (srcbb->succs); i++)
		{
		  edge srce = EDGE_SUCC (srcbb, i);
		  edge dste = EDGE_SUCC (dstbb, i);
		  dste->probability = 
		    dste->probability * dstbb->count.probability_in (dstbb->count + srcbb->count)
		    + srce->probability * srcbb->count.probability_in (dstbb->count + srcbb->count);
		}
	      dstbb->count += srcbb->count;
	    }
	}
      push_cfun (dstcfun);
      update_max_bb_count ();
      compute_function_frequency ();
      pop_cfun ();
      for (e = dst->callees; e; e = e->next_callee)
	{
	  if (e->speculative)
	    continue;
	  e->count = gimple_bb (e->call_stmt)->count;
	}
      for (e = dst->indirect_calls, e2 = src->indirect_calls; e;
	   e2 = (e2 ? e2->next_callee : NULL), e = e->next_callee)
	{
	  profile_count count = gimple_bb (e->call_stmt)->count;
	  /* When call is speculative, we need to re-distribute probabilities
	     the same way as they was.  This is not really correct because
	     in the other copy the speculation may differ; but probably it
	     is not really worth the effort.  */
	  if (e->speculative)
	    {
	      cgraph_edge *direct, *indirect;
	      cgraph_edge *direct2 = NULL, *indirect2 = NULL;
	      ipa_ref *ref;

	      e->speculative_call_info (direct, indirect, ref);
	      gcc_assert (e == indirect);
	      if (e2 && e2->speculative)
	        e2->speculative_call_info (direct2, indirect2, ref);
	      if (indirect->count > profile_count::zero ()
		  || direct->count > profile_count::zero ())
		{
		  /* We should mismatch earlier if there is no matching
		     indirect edge.  */
		  if (!e2)
		    {
		      if (dump_file)
		        fprintf (dump_file,
				 "Mismatch in merging indirect edges\n");
		    }
		  else if (!e2->speculative)
		    indirect->count += e2->count;
		  else if (e2->speculative)
		    {
		      if (DECL_ASSEMBLER_NAME (direct2->callee->decl)
			  != DECL_ASSEMBLER_NAME (direct->callee->decl))
			{
			  if (direct2->count >= direct->count)
			    {
			      direct->redirect_callee (direct2->callee);
			      indirect->count += indirect2->count
						 + direct->count;
			      direct->count = direct2->count;
			    }
			  else
			    indirect->count += indirect2->count + direct2->count;
			}
		      else
			{
			   direct->count += direct2->count;
			   indirect->count += indirect2->count;
			}
		    }
		}
	      else
		/* At the moment we should have only profile feedback based
		   speculations when merging.  */
		gcc_unreachable ();
	    }
	  else if (e2 && e2->speculative)
	    {
	      cgraph_edge *direct, *indirect;
	      ipa_ref *ref;

	      e2->speculative_call_info (direct, indirect, ref);
	      e->count = count;
	      e->make_speculative (direct->callee, direct->count);
	    }
	  else
	    e->count = count;
	}
      if (!preserve_body)
        src->release_body ();
      ipa_update_overall_fn_summary (dst);
    }
  /* TODO: if there is no match, we can scale up.  */
  src->decl = oldsrcdecl;
}

/* Return true if call to DEST is known to be self-recusive call withing FUNC.   */

bool
recursive_call_p (tree func, tree dest)
{
  struct cgraph_node *dest_node = cgraph_node::get_create (dest);
  struct cgraph_node *cnode = cgraph_node::get_create (func);
  ipa_ref *alias;
  enum availability avail;

  gcc_assert (!cnode->alias);
  if (cnode != dest_node->ultimate_alias_target (&avail))
    return false;
  if (avail >= AVAIL_AVAILABLE)
    return true;
  if (!dest_node->semantically_equivalent_p (cnode))
    return false;
  /* If there is only one way to call the fuction or we know all of them
     are semantically equivalent, we still can consider call recursive.  */
  FOR_EACH_ALIAS (cnode, alias)
    if (!dest_node->semantically_equivalent_p (alias->referring))
      return false;
  return true;
}