[thirdparty/gcc.git] / gcc / ipa-utils.cc

/* Utilities for ipa analysis.
   Copyright (C) 2005-2023 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;
  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->get_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))
        {
          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 (*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;

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

      if (avail > AVAIL_INTERPOSABLE
          || 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->get_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->inlined_to
                  && !node->alias && !node->thunk
                  && !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;
}

/* Scale function of calls in NODE by ratio ORIG_COUNT/NODE->count.  */

void
scale_ipa_profile_for_fn (struct cgraph_node *node, profile_count orig_count)
{
  profile_count to = node->count;
  profile_count::adjust_for_ipa_scaling (&to, &orig_count);
  struct cgraph_edge *e;
  
  for (e = node->callees; e; e = e->next_callee)
    e->count = e->count.apply_scale (to, orig_count);
  for (e = node->indirect_calls; e; e = e->next_callee)
    e->count = e->count.apply_scale (to, orig_count);
}

/* 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;
  bool copy_counts = false;

  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;

  /* Merging zero profile to dst is no-op.  */
  if (src->count.ipa () == profile_count::zero ())
    return;

  /* 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;
  profile_count orig_count = dst->count;

  /* 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 ((dst->count.ipa ().nonzero_p ()
       || src->count.ipa ().nonzero_p ())
      && dst->count.ipa ().initialized_p ()
      && src->count.ipa ().initialized_p ())
    dst->count = dst->count.ipa () + src->count.ipa ();
  else if (dst->count.ipa ().initialized_p ())
    ;
  else if (src->count.ipa ().initialized_p ())
    {
      copy_counts = true;
      dst->count = src->count.ipa ();
    }

  /* If no updating needed return early.  */
  if (dst->count == orig_count)
    return;

  if (symtab->dump_file)
    {
      fprintf (symtab->dump_file, "Merging profiles of %s count:",
               src->dump_name ());
      src->count.dump (symtab->dump_file);
      fprintf (symtab->dump_file, " to %s count:",
               dst->dump_name ());
      orig_count.dump (symtab->dump_file);
      fprintf (symtab->dump_file, " resulting count:");
      dst->count.dump (symtab->dump_file);
      fprintf (symtab->dump_file, "\n");
    }

  /* First handle functions with no gimple body.  */
  if (dst->thunk || dst->alias
      || src->thunk || src->alias)
    {
      scale_ipa_profile_for_fn (dst, orig_count);
      return;
    }

  /* 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;
      struct cgraph_edge *e, *e2;

      for (e = dst->callees, e2 = src->callees; e && e2 && match;
           e2 = e2->next_callee, e = e->next_callee)
        {
          if (gimple_bb (e->call_stmt)->index
              != gimple_bb (e2->call_stmt)->index)
            {
              if (symtab->dump_file)
                fprintf (symtab->dump_file,
                         "Giving up; call stmt mismatch.\n");
              match = false;
            }
        }
      if (e || e2)
        {
          if (symtab->dump_file)
            fprintf (symtab->dump_file,
                     "Giving up; number of calls differs.\n");
          match = false;
        }
      for (e = dst->indirect_calls, e2 = src->indirect_calls; e && e2 && match;
           e2 = e2->next_callee, e = e->next_callee)
        {
          if (gimple_bb (e->call_stmt)->index
              != gimple_bb (e2->call_stmt)->index)
            {
              if (symtab->dump_file)
                fprintf (symtab->dump_file,
                         "Giving up; indirect call stmt mismatch.\n");
              match = false;
            }
        }
      if (e || e2)
        {
          if (symtab->dump_file)
            fprintf (symtab->dump_file,
                     "Giving up; number of indirect calls differs.\n");
          match=false;
        }

      if (match)
        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 mismatch 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 mismatch for bb %i.\n",
                               srce->dest->index);
                    match = false;
                    break;
                  }
              }
          }
    }
  if (match)
    {
      struct cgraph_edge *e, *e2;
      basic_block srcbb, dstbb;

      /* Function and global profile may be out of sync.  First scale it same
         way as fixup_cfg would.  */
      profile_count srcnum = src->count;
      profile_count srcden = ENTRY_BLOCK_PTR_FOR_FN (srccfun)->count;
      bool srcscale = srcnum.initialized_p () && !(srcnum == srcden);
      profile_count dstnum = orig_count;
      profile_count dstden = ENTRY_BLOCK_PTR_FOR_FN (dstcfun)->count;
      bool dstscale = !copy_counts
                      && dstnum.initialized_p () && !(dstnum == dstden);

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

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

          profile_count srccount = srcbb->count;
          if (srcscale)
            srccount = srccount.apply_scale (srcnum, srcden);
          if (dstscale)
            dstbb->count = dstbb->count.apply_scale (dstnum, dstden);

          if (copy_counts)
            {
              dstbb->count = srccount;
              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 
            {
              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.ipa ().probability_in
                                                 (dstbb->count.ipa ()
                                                  + srccount.ipa ())
                    + srce->probability * srcbb->count.ipa ().probability_in
                                                 (dstbb->count.ipa ()
                                                  + srccount.ipa ());
                }
              dstbb->count = dstbb->count.ipa () + srccount.ipa ();
            }
        }
      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)
        {
          if (!e->speculative && !e2->speculative)
            {
              /* FIXME: we need to also merge ipa-profile histograms
                 because with LTO merging happens from lto-symtab before
                 these are converted to indirect edges.  */
              e->count = gimple_bb (e->call_stmt)->count;
              continue;
            }

          /* When copying just remove all speuclations on dst and then copy
             one from src.  */
          if (copy_counts)
            {
              while (e->speculative)
                cgraph_edge::resolve_speculation (e, NULL);
              e->count = gimple_bb (e->call_stmt)->count;
              if (e2->speculative)
                {
                  for (cgraph_edge *e3 = e2->first_speculative_call_target ();
                       e3;
                       e3 = e3->next_speculative_call_target ())
                    {
                      cgraph_edge *ns;
                      ns = e->make_speculative
                         (dyn_cast <cgraph_node *>
                            (e3->speculative_call_target_ref ()->referred),
                             e3->count, e3->speculative_id);
                      /* Target may differ from ref (for example it may be
                         redirected to local alias.  */
                      ns->redirect_callee (e3->callee);
                    }
                }
              continue;
            }

          /* Iterate all speculations in SRC, see if corresponding ones exist
             int DST and if so, sum the counts.  Otherwise create new
             speculation.  */
          int max_spec = 0;
          for (cgraph_edge *e3 = e->first_speculative_call_target ();
               e3;
               e3 = e3->next_speculative_call_target ())
            if (e3->speculative_id > max_spec)
              max_spec = e3->speculative_id;
          for (cgraph_edge *e3 = e2->first_speculative_call_target ();
               e3;
               e3 = e3->next_speculative_call_target ())
            {
              cgraph_edge *te
                 = e->speculative_call_for_target
                         (dyn_cast <cgraph_node *>
                            (e3->speculative_call_target_ref ()->referred));
              if (te)
                te->count = te->count + e3->count;
              else
                {
                  e->count = e->count + e3->count;
                  cgraph_edge *ns;
                  ns = e->make_speculative
                         (dyn_cast <cgraph_node *>
                            (e3->speculative_call_target_ref ()
                             ->referred),
                          e3->count,
                          e3->speculative_id + max_spec + 1);
                  /* Target may differ from ref (for example it may be
                     redirected to local alias.  */
                  ns->redirect_callee (e3->callee);
                }
            }
        }
      if (!preserve_body)
        src->release_body ();
      /* Update summary.  */
      compute_fn_summary (dst, 0);
    }
  /* We can't update CFG profile, but we can scale IPA profile. CFG
     will be scaled according to dst->count after IPA passes.  */
  else
    scale_ipa_profile_for_fn (dst, orig_count);
  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;
}