gcc/analyzer/supergraph.cc

/* "Supergraph" classes that combine CFGs and callgraph into one digraph.
   Copyright (C) 2019-2021 Free Software Foundation, Inc.
   Contributed by David Malcolm <dmalcolm@redhat.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 "tree.h"
#include "tm.h"
#include "toplev.h"
#include "hash-table.h"
#include "vec.h"
#include "ggc.h"
#include "basic-block.h"
#include "function.h"
#include "gimple-fold.h"
#include "tree-eh.h"
#include "gimple-expr.h"
#include "is-a.h"
#include "timevar.h"
#include "gimple.h"
#include "gimple-iterator.h"
#include "gimple-pretty-print.h"
#include "tree-pretty-print.h"
#include "graphviz.h"
#include "cgraph.h"
#include "tree-dfa.h"
#include "cfganal.h"
#include "function.h"
#include "json.h"
#include "analyzer/analyzer.h"
#include "ordered-hash-map.h"
#include "options.h"
#include "cgraph.h"
#include "cfg.h"
#include "digraph.h"
#include "analyzer/supergraph.h"
#include "analyzer/analyzer-logging.h"

#if ENABLE_ANALYZER

namespace ana {

/* Get the function of the ultimate alias target being called at EDGE,
   if any.  */

static function *
get_ultimate_function_for_cgraph_edge (cgraph_edge *edge)
{
  cgraph_node *ultimate_node = edge->callee->ultimate_alias_target ();
  if (!ultimate_node)
    return NULL;
  return ultimate_node->get_fun ();
}

/* Get the cgraph_edge, but only if there's an underlying function body.  */

cgraph_edge *
supergraph_call_edge (function *fun, gimple *stmt)
{
  gcall *call = dyn_cast<gcall *> (stmt);
  if (!call)
    return NULL;
  cgraph_edge *edge = cgraph_node::get (fun->decl)->get_edge (stmt);
  if (!edge)
    return NULL;
  if (!edge->callee)
    return NULL; /* e.g. for a function pointer.  */
  if (!get_ultimate_function_for_cgraph_edge (edge))
    return NULL;
  return edge;
}

/* class saved_uids.

   In order to ensure consistent results without relying on the ordering
   of pointer values we assign a uid to each gimple stmt, globally unique
   across all functions.

   Normally, the stmt uids are a scratch space that each pass can freely
   assign its own values to.  However, in the case of LTO, the uids are
   used to associate call stmts with callgraph edges between the WPA phase
   (where the analyzer runs in LTO mode) and the LTRANS phase; if the
   analyzer changes them in the WPA phase, it leads to errors when
   streaming the code back in at LTRANS.
   lto_prepare_function_for_streaming has code to renumber the stmt UIDs
   when the code is streamed back out, but for some reason this isn't
   called for clones.

   Hence, as a workaround, this class has responsibility for tracking
   the original uids and restoring them once the pass is complete
   (in the supergraph dtor).  */

/* Give STMT a globally unique uid, storing its original uid so it can
   later be restored.  */

void
saved_uids::make_uid_unique (gimple *stmt)
{
  unsigned next_uid = m_old_stmt_uids.length ();
  unsigned old_stmt_uid = stmt->uid;
  stmt->uid = next_uid;
  m_old_stmt_uids.safe_push
    (std::pair<gimple *, unsigned> (stmt, old_stmt_uid));
}

/* Restore the saved uids of all stmts.  */

void
saved_uids::restore_uids () const
{
  unsigned i;
  std::pair<gimple *, unsigned> *pair;
  FOR_EACH_VEC_ELT (m_old_stmt_uids, i, pair)
    pair->first->uid = pair->second;
}

/* supergraph's ctor.  Walk the callgraph, building supernodes for each
   CFG basic block, splitting the basic blocks at callsites.  Join
   together the supernodes with interprocedural and intraprocedural
   superedges as appropriate.
   Assign UIDs to the gimple stmts.  */

supergraph::supergraph (logger *logger)
{
  auto_timevar tv (TV_ANALYZER_SUPERGRAPH);

  LOG_FUNC (logger);

  /* First pass: make supernodes (and assign UIDs to the gimple stmts).  */
  {
    /* Sort the cgraph_nodes?  */
    cgraph_node *node;
    FOR_EACH_FUNCTION_WITH_GIMPLE_BODY (node)
    {
      function *fun = node->get_fun ();

      /* Ensure that EDGE_DFS_BACK is correct for every CFG edge in
	 the supergraph (by doing it per-function).  */
      auto_cfun sentinel (fun);
      mark_dfs_back_edges ();

      const int start_idx = m_nodes.length ();

      basic_block bb;
      FOR_ALL_BB_FN (bb, fun)
	{
	  /* The initial supernode for the BB gets the phi nodes (if any).  */
	  supernode *node_for_stmts = add_node (fun, bb, NULL, phi_nodes (bb));
	  m_bb_to_initial_node.put (bb, node_for_stmts);
	  for (gphi_iterator gpi = gsi_start_phis (bb); !gsi_end_p (gpi);
	       gsi_next (&gpi))
	    {
	      gimple *stmt = gsi_stmt (gpi);
	      m_stmt_to_node_t.put (stmt, node_for_stmts);
	      m_stmt_uids.make_uid_unique (stmt);
	    }

	  /* Append statements from BB to the current supernode, splitting
	     them into a new supernode at each call site; such call statements
	     appear in both supernodes (representing call and return).  */
	  gimple_stmt_iterator gsi;
	  for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
	    {
	      gimple *stmt = gsi_stmt (gsi);
	      node_for_stmts->m_stmts.safe_push (stmt);
	      m_stmt_to_node_t.put (stmt, node_for_stmts);
	      m_stmt_uids.make_uid_unique (stmt);
	      if (cgraph_edge *edge = supergraph_call_edge (fun, stmt))
		{
		  m_cgraph_edge_to_caller_prev_node.put(edge, node_for_stmts);
		  node_for_stmts = add_node (fun, bb, as_a <gcall *> (stmt), NULL);
		  m_cgraph_edge_to_caller_next_node.put (edge, node_for_stmts);
		}
	    }

	  m_bb_to_final_node.put (bb, node_for_stmts);
	}

      const unsigned num_snodes = m_nodes.length () - start_idx;
      m_function_to_num_snodes.put (fun, num_snodes);

      if (logger)
	{
	  const int end_idx = m_nodes.length () - 1;
	  logger->log ("SN: %i...%i: function %qD",
		       start_idx, end_idx, fun->decl);
	}
    }
  }

  /* Second pass: make superedges.  */
  {
    /* Make superedges for CFG edges.  */
    for (bb_to_node_t::iterator iter = m_bb_to_final_node.begin ();
	 iter != m_bb_to_final_node.end ();
	 ++iter)
      {
	basic_block bb = (*iter).first;
	supernode *src_supernode = (*iter).second;

	::edge cfg_edge;
	int idx;
	if (bb->succs)
	  FOR_EACH_VEC_ELT (*bb->succs, idx, cfg_edge)
	    {
	      basic_block dest_cfg_block = cfg_edge->dest;
	      supernode *dest_supernode
		= *m_bb_to_initial_node.get (dest_cfg_block);
	      cfg_superedge *cfg_sedge
		= add_cfg_edge (src_supernode, dest_supernode, cfg_edge, idx);
	      m_cfg_edge_to_cfg_superedge.put (cfg_edge, cfg_sedge);
	    }
      }

    /* Make interprocedural superedges for calls.  */
    {
      for (cgraph_edge_to_node_t::iterator iter
	     = m_cgraph_edge_to_caller_prev_node.begin ();
	   iter != m_cgraph_edge_to_caller_prev_node.end ();
	   ++iter)
	{
	  cgraph_edge *edge = (*iter).first;
	  supernode *caller_prev_supernode = (*iter).second;
	  function* callee_fn = get_ultimate_function_for_cgraph_edge (edge);
	  if (!callee_fn || !callee_fn->cfg)
	    continue;
	  basic_block callee_cfg_block = ENTRY_BLOCK_PTR_FOR_FN (callee_fn);
	  supernode *callee_supernode
	    = *m_bb_to_initial_node.get (callee_cfg_block);
	  call_superedge *sedge
	    = add_call_superedge (caller_prev_supernode,
				  callee_supernode,
				  edge);
	  m_cgraph_edge_to_call_superedge.put (edge, sedge);
	}
    }

    /* Make interprocedural superedges for returns.  */
    {
      for (cgraph_edge_to_node_t::iterator iter
	     = m_cgraph_edge_to_caller_next_node.begin ();
	   iter != m_cgraph_edge_to_caller_next_node.end ();
	   ++iter)
	{
	  cgraph_edge *edge = (*iter).first;
	  supernode *caller_next_supernode = (*iter).second;
	  function* callee_fn = get_ultimate_function_for_cgraph_edge (edge);
	  if (!callee_fn || !callee_fn->cfg)
	    continue;
	  basic_block callee_cfg_block = EXIT_BLOCK_PTR_FOR_FN (callee_fn);
	  supernode *callee_supernode
	    = *m_bb_to_initial_node.get (callee_cfg_block);
	  return_superedge *sedge
	    = add_return_superedge (callee_supernode,
				    caller_next_supernode,
				    edge);
	  m_cgraph_edge_to_return_superedge.put (edge, sedge);
	}
    }

    /* Make intraprocedural superedges linking the two halves of a call.  */
    {
      for (cgraph_edge_to_node_t::iterator iter
	     = m_cgraph_edge_to_caller_prev_node.begin ();
	   iter != m_cgraph_edge_to_caller_prev_node.end ();
	   ++iter)
	{
	  cgraph_edge *edge = (*iter).first;
	  supernode *caller_prev_supernode = (*iter).second;
	  supernode *caller_next_supernode
	    = *m_cgraph_edge_to_caller_next_node.get (edge);
	  superedge *sedge
	    = new callgraph_superedge (caller_prev_supernode,
				       caller_next_supernode,
				       SUPEREDGE_INTRAPROCEDURAL_CALL,
				       edge);
	  add_edge (sedge);
	  m_cgraph_edge_to_intraproc_superedge.put (edge, sedge);
	}

    }
  }
}

/* supergraph's dtor.  Reset stmt uids.  */

supergraph::~supergraph ()
{
  m_stmt_uids.restore_uids ();
}

/* Dump this graph in .dot format to PP, using DUMP_ARGS.
   Cluster the supernodes by function, then by BB from original CFG.  */

void
supergraph::dump_dot_to_pp (pretty_printer *pp,
			    const dump_args_t &dump_args) const
{
  graphviz_out gv (pp);

  pp_string (pp, "digraph \"");
  pp_write_text_to_stream (pp);
  pp_string (pp, "supergraph");
  pp_write_text_as_dot_label_to_stream (pp, /*for_record=*/false);
  pp_string (pp, "\" {\n");
  gv.indent ();

  gv.println ("overlap=false;");
  gv.println ("compound=true;");

  /* TODO: maybe (optionally) sub-subdivide by TU, for LTO; see also:
     https://gcc-python-plugin.readthedocs.io/en/latest/_images/sample-supergraph.png
  */

  /* Break out the supernodes into clusters by function.  */
  {
    cgraph_node *node;
    FOR_EACH_FUNCTION_WITH_GIMPLE_BODY (node)
    {
      function *fun = node->get_fun ();
      const char *funcname = function_name (fun);
      gv.println ("subgraph \"cluster_%s\" {",
		  funcname);
      gv.indent ();
      pp_printf (pp,
		 ("style=\"dashed\";"
		  " color=\"black\";"
		  " label=\"%s\";\n"),
		 funcname);

      /* Break out the nodes into clusters by BB from original CFG.  */
      {
	basic_block bb;
	FOR_ALL_BB_FN (bb, fun)
	  {
	    if (dump_args.m_flags & SUPERGRAPH_DOT_SHOW_BBS)
	      {
		gv.println ("subgraph \"cluster_%s_bb_%i\" {",
			    funcname, bb->index);
		gv.indent ();
		pp_printf (pp,
			   ("style=\"dashed\";"
			    " color=\"black\";"
			    " label=\"bb: %i\";\n"),
			   bb->index);
	      }

	    // TODO: maybe keep an index per-function/per-bb to speed this up???
	    int i;
	    supernode *n;
	    FOR_EACH_VEC_ELT (m_nodes, i, n)
	      if (n->m_fun == fun && n->m_bb == bb)
		n->dump_dot (&gv, dump_args);

	    if (dump_args.m_flags & SUPERGRAPH_DOT_SHOW_BBS)
	      {
		/* Terminate per-bb "subgraph" */
		gv.outdent ();
		gv.println ("}");
	      }
	  }
      }

      /* Add an invisible edge from ENTRY to EXIT, to improve the graph layout.  */
      pp_string (pp, "\t");
      get_node_for_function_entry (fun)->dump_dot_id (pp);
      pp_string (pp, ":s -> ");
      get_node_for_function_exit (fun)->dump_dot_id (pp);
      pp_string (pp, ":n [style=\"invis\",constraint=true];\n");

      /* Terminate per-function "subgraph" */
      gv.outdent ();
      gv.println ("}");
    }
  }

  /* Superedges.  */
  int i;
  superedge *e;
  FOR_EACH_VEC_ELT (m_edges, i, e)
    e->dump_dot (&gv, dump_args);

  /* Terminate "digraph" */
  gv.outdent ();
  gv.println ("}");
}

/* Dump this graph in .dot format to FP, using DUMP_ARGS.  */

void
supergraph::dump_dot_to_file (FILE *fp, const dump_args_t &dump_args) const
{
  pretty_printer *pp = global_dc->printer->clone ();
  pp_show_color (pp) = 0;
  /* %qE in logs for SSA_NAMEs should show the ssa names, rather than
     trying to prettify things by showing the underlying var.  */
  pp_format_decoder (pp) = default_tree_printer;

  pp->buffer->stream = fp;
  dump_dot_to_pp (pp, dump_args);
  pp_flush (pp);
  delete pp;
}

/* Dump this graph in .dot format to PATH, using DUMP_ARGS.  */

void
supergraph::dump_dot (const char *path, const dump_args_t &dump_args) const
{
  FILE *fp = fopen (path, "w");
  dump_dot_to_file (fp, dump_args);
  fclose (fp);
}

/* Return a new json::object of the form
   {"nodes" : [objs for snodes],
    "edges" : [objs for sedges]}.  */

json::object *
supergraph::to_json () const
{
  json::object *sgraph_obj = new json::object ();

  /* Nodes.  */
  {
    json::array *nodes_arr = new json::array ();
    unsigned i;
    supernode *n;
    FOR_EACH_VEC_ELT (m_nodes, i, n)
      nodes_arr->append (n->to_json ());
    sgraph_obj->set ("nodes", nodes_arr);
  }

  /* Edges.  */
  {
    json::array *edges_arr = new json::array ();
    unsigned i;
    superedge *n;
    FOR_EACH_VEC_ELT (m_edges, i, n)
      edges_arr->append (n->to_json ());
    sgraph_obj->set ("edges", edges_arr);
  }

  return sgraph_obj;
}

/* Create a supernode for BB within FUN and add it to this supergraph.

   If RETURNING_CALL is non-NULL, the supernode represents the resumption
   of the basic block after returning from that call.

   If PHI_NODES is non-NULL, this is the initial supernode for the basic
   block, and is responsible for any handling of the phi nodes.  */

supernode *
supergraph::add_node (function *fun, basic_block bb, gcall *returning_call,
		      gimple_seq phi_nodes)
{
  supernode *n = new supernode (fun, bb, returning_call, phi_nodes,
				m_nodes.length ());
  m_nodes.safe_push (n);
  return n;
}

/* Create a new cfg_superedge from SRC to DEST for the underlying CFG edge E,
   adding it to this supergraph.

   If the edge is for a switch statement, create a switch_cfg_superedge
   subclass using IDX (the index of E within the out-edges from SRC's
   underlying basic block).  */

cfg_superedge *
supergraph::add_cfg_edge (supernode *src, supernode *dest, ::edge e, int idx)
{
  /* Special-case switch edges.  */
  gimple *stmt = src->get_last_stmt ();
  cfg_superedge *new_edge;
  if (stmt && stmt->code == GIMPLE_SWITCH)
    new_edge = new switch_cfg_superedge (src, dest, e, idx);
  else
    new_edge = new cfg_superedge (src, dest, e);
  add_edge (new_edge);
  return new_edge;
}

/* Create and add a call_superedge representing an interprocedural call
   from SRC to DEST, using CEDGE.  */

call_superedge *
supergraph::add_call_superedge (supernode *src, supernode *dest,
				cgraph_edge *cedge)
{
  call_superedge *new_edge = new call_superedge (src, dest, cedge);
  add_edge (new_edge);
  return new_edge;
}

/* Create and add a return_superedge representing returning from an
   interprocedural call, returning from SRC to DEST, using CEDGE.  */

return_superedge *
supergraph::add_return_superedge (supernode *src, supernode *dest,
				  cgraph_edge *cedge)
{
  return_superedge *new_edge = new return_superedge (src, dest, cedge);
  add_edge (new_edge);
  return new_edge;
}

/* Implementation of dnode::dump_dot vfunc for supernodes.

   Write a cluster for the node, and within it a .dot node showing
   the phi nodes and stmts.  Call into any node annotator from ARGS to
   potentially add other records to the cluster.  */

void
supernode::dump_dot (graphviz_out *gv, const dump_args_t &args) const
{
  gv->println ("subgraph cluster_node_%i {",
	       m_index);
  gv->indent ();

  gv->println("style=\"solid\";");
  gv->println("color=\"black\";");
  gv->println("fillcolor=\"lightgrey\";");
  gv->println("label=\"sn: %i (bb: %i)\";", m_index, m_bb->index);

  pretty_printer *pp = gv->get_pp ();

  if (args.m_node_annotator)
    args.m_node_annotator->add_node_annotations (gv, *this, false);

  gv->write_indent ();
  dump_dot_id (pp);
  pp_printf (pp,
	     " [shape=none,margin=0,style=filled,fillcolor=%s,label=<",
	     "lightgrey");
  pp_string (pp, "<TABLE BORDER=\"0\">");
  pp_write_text_to_stream (pp);

  bool had_row = false;

  /* Give any annotator the chance to add its own per-node TR elements. */
  if (args.m_node_annotator)
    if (args.m_node_annotator->add_node_annotations (gv, *this, true))
      had_row = true;

  if (m_returning_call)
    {
      gv->begin_trtd ();
      pp_string (pp, "returning call: ");
      gv->end_tdtr ();

      gv->begin_tr ();
      gv->begin_td ();
      pp_gimple_stmt_1 (pp, m_returning_call, 0, (dump_flags_t)0);
      pp_write_text_as_html_like_dot_to_stream (pp);
      gv->end_td ();
      /* Give any annotator the chance to add per-stmt TD elements to
	 this row.  */
      if (args.m_node_annotator)
	args.m_node_annotator->add_stmt_annotations (gv, m_returning_call,
						     true);
      gv->end_tr ();

      /* Give any annotator the chance to add per-stmt TR elements.  */
      if (args.m_node_annotator)
	args.m_node_annotator->add_stmt_annotations (gv, m_returning_call,
						     false);
      pp_newline (pp);

      had_row = true;
    }

  if (entry_p ())
    {
      pp_string (pp, "<TR><TD>ENTRY</TD></TR>");
      pp_newline (pp);
      had_row = true;
    }

  if (return_p ())
    {
      pp_string (pp, "<TR><TD>EXIT</TD></TR>");
      pp_newline (pp);
      had_row = true;
    }

  /* Phi nodes.  */
  for (gphi_iterator gpi = const_cast<supernode *> (this)->start_phis ();
       !gsi_end_p (gpi); gsi_next (&gpi))
    {
      const gimple *stmt = gsi_stmt (gpi);
      gv->begin_tr ();
      gv->begin_td ();
      pp_gimple_stmt_1 (pp, stmt, 0, (dump_flags_t)0);
      pp_write_text_as_html_like_dot_to_stream (pp);
      gv->end_td ();
      /* Give any annotator the chance to add per-phi TD elements to
	 this row.  */
      if (args.m_node_annotator)
	args.m_node_annotator->add_stmt_annotations (gv, stmt, true);
      gv->end_tr ();

      /* Give any annotator the chance to add per-phi TR elements.  */
      if (args.m_node_annotator)
	args.m_node_annotator->add_stmt_annotations (gv, stmt, false);

      pp_newline (pp);
      had_row = true;
    }

  /* Statements.  */
  int i;
  gimple *stmt;
  FOR_EACH_VEC_ELT (m_stmts, i, stmt)
    {
      gv->begin_tr ();
      gv->begin_td ();
      pp_gimple_stmt_1 (pp, stmt, 0, (dump_flags_t)0);
      pp_write_text_as_html_like_dot_to_stream (pp);
      gv->end_td ();
      /* Give any annotator the chance to add per-stmt TD elements to
	 this row.  */
      if (args.m_node_annotator)
	args.m_node_annotator->add_stmt_annotations (gv, stmt, true);
      gv->end_tr ();

      /* Give any annotator the chance to add per-stmt TR elements.  */
      if (args.m_node_annotator)
	args.m_node_annotator->add_stmt_annotations (gv, stmt, false);

      pp_newline (pp);
      had_row = true;
    }

  /* Give any annotator the chance to add additional per-node TR elements
     to the end of the TABLE. */
  if (args.m_node_annotator)
    if (args.m_node_annotator->add_after_node_annotations (gv, *this))
      had_row = true;

  /* Graphviz requires a TABLE element to have at least one TR
     (and each TR to have at least one TD).  */
  if (!had_row)
    {
      pp_string (pp, "<TR><TD>(empty)</TD></TR>");
      pp_newline (pp);
    }

  pp_string (pp, "</TABLE>>];\n\n");
  pp_flush (pp);

  /* Terminate "subgraph" */
  gv->outdent ();
  gv->println ("}");
}

/* Write an ID for this node to PP, for use in .dot output.  */

void
supernode::dump_dot_id (pretty_printer *pp) const
{
  pp_printf (pp, "node_%i", m_index);
}

/* Return a new json::object of the form
   {"idx": int,
    "fun": optional str
    "bb_idx": int,
    "returning_call": optional str,
    "phis": [str],
    "stmts" : [str]}.  */

json::object *
supernode::to_json () const
{
  json::object *snode_obj = new json::object ();

  snode_obj->set ("idx", new json::integer_number (m_index));
  snode_obj->set ("bb_idx", new json::integer_number (m_bb->index));
  if (function *fun = get_function ())
    snode_obj->set ("fun", new json::string (function_name (fun)));

  if (m_returning_call)
    {
      pretty_printer pp;
      pp_format_decoder (&pp) = default_tree_printer;
      pp_gimple_stmt_1 (&pp, m_returning_call, 0, (dump_flags_t)0);
      snode_obj->set ("returning_call",
		      new json::string (pp_formatted_text (&pp)));
    }

  /* Phi nodes.  */
  {
    json::array *phi_arr = new json::array ();
    for (gphi_iterator gpi = const_cast<supernode *> (this)->start_phis ();
	 !gsi_end_p (gpi); gsi_next (&gpi))
      {
	const gimple *stmt = gsi_stmt (gpi);
	pretty_printer pp;
	pp_format_decoder (&pp) = default_tree_printer;
	pp_gimple_stmt_1 (&pp, stmt, 0, (dump_flags_t)0);
	phi_arr->append (new json::string (pp_formatted_text (&pp)));
      }
    snode_obj->set ("phis", phi_arr);
  }

  /* Statements.  */
  {
    json::array *stmt_arr = new json::array ();
    int i;
    gimple *stmt;
    FOR_EACH_VEC_ELT (m_stmts, i, stmt)
      {
	pretty_printer pp;
	pp_format_decoder (&pp) = default_tree_printer;
	pp_gimple_stmt_1 (&pp, stmt, 0, (dump_flags_t)0);
	stmt_arr->append (new json::string (pp_formatted_text (&pp)));
      }
    snode_obj->set ("stmts", stmt_arr);
  }

  return snode_obj;
}

/* Get a location_t for the start of this supernode.  */

location_t
supernode::get_start_location () const
{
  if (m_returning_call
      && get_pure_location (m_returning_call->location) != UNKNOWN_LOCATION)
    return m_returning_call->location;

  int i;
  gimple *stmt;
  FOR_EACH_VEC_ELT (m_stmts, i, stmt)
    if (get_pure_location (stmt->location) != UNKNOWN_LOCATION)
      return stmt->location;

  if (entry_p ())
    {
      // TWEAK: show the decl instead; this leads to more readable output:
      return DECL_SOURCE_LOCATION (m_fun->decl);

      return m_fun->function_start_locus;
    }
  if (return_p ())
    return m_fun->function_end_locus;

  return UNKNOWN_LOCATION;
}

/* Get a location_t for the end of this supernode.  */

location_t
supernode::get_end_location () const
{
  int i;
  gimple *stmt;
  FOR_EACH_VEC_ELT_REVERSE (m_stmts, i, stmt)
    if (get_pure_location (stmt->location) != UNKNOWN_LOCATION)
      return stmt->location;

  if (m_returning_call
      && get_pure_location (m_returning_call->location) != UNKNOWN_LOCATION)
    return m_returning_call->location;

  if (entry_p ())
    return m_fun->function_start_locus;
  if (return_p ())
    return m_fun->function_end_locus;

  return UNKNOWN_LOCATION;
}

/* Given STMT within this supernode, return its index within m_stmts.  */

unsigned int
supernode::get_stmt_index (const gimple *stmt) const
{
  unsigned i;
  gimple *iter_stmt;
  FOR_EACH_VEC_ELT (m_stmts, i, iter_stmt)
    if (iter_stmt == stmt)
      return i;
  gcc_unreachable ();
}

/* Get a string for PK.  */

static const char *
edge_kind_to_string (enum edge_kind kind)
{
  switch (kind)
    {
    default:
      gcc_unreachable ();
    case SUPEREDGE_CFG_EDGE:
      return "SUPEREDGE_CFG_EDGE";
    case SUPEREDGE_CALL:
      return "SUPEREDGE_CALL";
    case SUPEREDGE_RETURN:
      return "SUPEREDGE_RETURN";
    case SUPEREDGE_INTRAPROCEDURAL_CALL:
      return "SUPEREDGE_INTRAPROCEDURAL_CALL";
    }
};

/* Dump this superedge to PP.  */

void
superedge::dump (pretty_printer *pp) const
{
  pp_printf (pp, "edge: SN: %i -> SN: %i", m_src->m_index, m_dest->m_index);
  char *desc = get_description (false);
  if (strlen (desc) > 0)
    {
      pp_space (pp);
      pp_string (pp, desc);
    }
  free (desc);
}

/* Dump this superedge to stderr.  */

DEBUG_FUNCTION void
superedge::dump () const
{
  pretty_printer pp;
  pp_format_decoder (&pp) = default_tree_printer;
  pp_show_color (&pp) = pp_show_color (global_dc->printer);
  pp.buffer->stream = stderr;
  dump (&pp);
  pp_newline (&pp);
  pp_flush (&pp);
}

/* Implementation of dedge::dump_dot for superedges.
   Write a .dot edge to GV representing this superedge.  */

void
superedge::dump_dot (graphviz_out *gv, const dump_args_t &) const
{
  const char *style = "\"solid,bold\"";
  const char *color = "black";
  int weight = 10;
  const char *constraint = "true";

  switch (m_kind)
    {
    default:
      gcc_unreachable ();
    case SUPEREDGE_CFG_EDGE:
      break;
    case SUPEREDGE_CALL:
      color = "red";
      break;
    case SUPEREDGE_RETURN:
      color = "green";
      break;
    case SUPEREDGE_INTRAPROCEDURAL_CALL:
      style = "\"dotted\"";
      break;
    }

  /* Adapted from graph.c:draw_cfg_node_succ_edges.  */
  if (::edge cfg_edge = get_any_cfg_edge ())
    {
      if (cfg_edge->flags & EDGE_FAKE)
	{
	  style = "dotted";
	  color = "green";
	  weight = 0;
	}
      else if (cfg_edge->flags & EDGE_DFS_BACK)
	{
	  style = "\"dotted,bold\"";
	  color = "blue";
	  weight = 10;
	}
      else if (cfg_edge->flags & EDGE_FALLTHRU)
	{
	  color = "blue";
	  weight = 100;
	}

      if (cfg_edge->flags & EDGE_ABNORMAL)
	color = "red";
    }

  gv->write_indent ();

  pretty_printer *pp = gv->get_pp ();

  m_src->dump_dot_id (pp);
  pp_string (pp, " -> ");
  m_dest->dump_dot_id (pp);
  pp_printf (pp,
	     (" [style=%s, color=%s, weight=%d, constraint=%s,"
	      " ltail=\"cluster_node_%i\", lhead=\"cluster_node_%i\""
	      " headlabel=\""),
	     style, color, weight, constraint,
	     m_src->m_index, m_dest->m_index);

  dump_label_to_pp (pp, false);

  pp_printf (pp, "\"];\n");
}

/* Return a new json::object of the form
   {"kind"   : str,
    "src_idx": int, the index of the source supernode,
    "dst_idx": int, the index of the destination supernode,
    "desc"   : str.  */

json::object *
superedge::to_json () const
{
  json::object *sedge_obj = new json::object ();
  sedge_obj->set ("kind", new json::string (edge_kind_to_string (m_kind)));
  sedge_obj->set ("src_idx", new json::integer_number (m_src->m_index));
  sedge_obj->set ("dst_idx", new json::integer_number (m_dest->m_index));

  {
    pretty_printer pp;
    pp_format_decoder (&pp) = default_tree_printer;
    dump_label_to_pp (&pp, false);
    sedge_obj->set ("desc", new json::string (pp_formatted_text (&pp)));
  }

  return sedge_obj;
}

/* If this is an intraprocedural superedge, return the associated
   CFG edge.  Otherwise, return NULL.  */

::edge
superedge::get_any_cfg_edge () const
{
  if (const cfg_superedge *sub = dyn_cast_cfg_superedge ())
    return sub->get_cfg_edge ();
  return NULL;
}

/* If this is an interprocedural superedge, return the associated
   cgraph_edge *.  Otherwise, return NULL.  */

cgraph_edge *
superedge::get_any_callgraph_edge () const
{
  if (const callgraph_superedge *sub = dyn_cast_callgraph_superedge ())
    return sub->m_cedge;
  return NULL;
}

/* Build a description of this superedge (e.g. "true" for the true
   edge of a conditional, or "case 42:" for a switch case).

   The caller is responsible for freeing the result.

   If USER_FACING is false, the result also contains any underlying
   CFG edge flags. e.g. " (flags FALLTHRU | DFS_BACK)".  */

char *
superedge::get_description (bool user_facing) const
{
  pretty_printer pp;
  dump_label_to_pp (&pp, user_facing);
  return xstrdup (pp_formatted_text (&pp));
}

/* Implementation of superedge::dump_label_to_pp for non-switch CFG
   superedges.

   For true/false edges, print "true" or "false" to PP.

   If USER_FACING is false, also print flags on the underlying CFG edge to
   PP.  */

void
cfg_superedge::dump_label_to_pp (pretty_printer *pp,
				 bool user_facing) const
{
  if (true_value_p ())
    pp_printf (pp, "true");
  else if (false_value_p ())
    pp_printf (pp, "false");

  if (user_facing)
    return;

  /* Express edge flags as a string with " | " separator.
     e.g. " (flags FALLTHRU | DFS_BACK)".  */
  if (get_flags ())
    {
      pp_string (pp, " (flags ");
      bool seen_flag = false;
#define DEF_EDGE_FLAG(NAME,IDX)			\
  do {						\
    if (get_flags () & EDGE_##NAME)			\
      {						\
	if (seen_flag)				\
	  pp_string (pp, " | ");			\
	pp_printf (pp, "%s", (#NAME));		\
	seen_flag = true;			\
      }						\
  } while (0);
#include "cfg-flags.def"
#undef DEF_EDGE_FLAG
      pp_string (pp, ")");
    }

  /* Otherwise, no label.  */
}

/* Get the phi argument for PHI for this CFG edge.  */

tree
cfg_superedge::get_phi_arg (const gphi *phi) const
{
  size_t index = m_cfg_edge->dest_idx;
  return gimple_phi_arg_def (phi, index);
}

/* Implementation of superedge::dump_label_to_pp for CFG superedges for
   "switch" statements.

   Print "case VAL:", "case LOWER ... UPPER:", or "default:" to PP.  */

void
switch_cfg_superedge::dump_label_to_pp (pretty_printer *pp,
					bool user_facing ATTRIBUTE_UNUSED) const
{
  tree case_label = get_case_label ();
  gcc_assert (TREE_CODE (case_label) == CASE_LABEL_EXPR);
  tree lower_bound = CASE_LOW (case_label);
  tree upper_bound = CASE_HIGH (case_label);
  if (lower_bound)
    {
      pp_printf (pp, "case ");
      dump_generic_node (pp, lower_bound, 0, (dump_flags_t)0, false);
      if (upper_bound)
	{
	  pp_printf (pp, " ... ");
	  dump_generic_node (pp, upper_bound, 0, (dump_flags_t)0, false);
	}
      pp_printf (pp, ":");
    }
  else
    pp_printf (pp, "default:");
}

/* Get the case label for this "switch" superedge.  */

tree
switch_cfg_superedge::get_case_label () const
{
  return gimple_switch_label (get_switch_stmt (), m_idx);
}

/* Implementation of superedge::dump_label_to_pp for interprocedural
   superedges.  */

void
callgraph_superedge::dump_label_to_pp (pretty_printer *pp,
				       bool user_facing ATTRIBUTE_UNUSED) const
{
  switch (m_kind)
    {
    default:
    case SUPEREDGE_CFG_EDGE:
      gcc_unreachable ();

    case SUPEREDGE_CALL:
      pp_printf (pp, "call");
      break;

    case SUPEREDGE_RETURN:
      pp_printf (pp, "return");
      break;

    case SUPEREDGE_INTRAPROCEDURAL_CALL:
      pp_printf (pp, "intraproc link");
      break;
    }
}

/* Get the function that was called at this interprocedural call/return
   edge.  */

function *
callgraph_superedge::get_callee_function () const
{
  return get_ultimate_function_for_cgraph_edge (m_cedge);
}

/* Get the calling function at this interprocedural call/return edge.  */

function *
callgraph_superedge::get_caller_function () const
{
  return m_cedge->caller->get_fun ();
}

/* Get the fndecl that was called at this interprocedural call/return
   edge.  */

tree
callgraph_superedge::get_callee_decl () const
{
  return get_callee_function ()->decl;
}

/* Get the calling fndecl at this interprocedural call/return edge.  */

tree
callgraph_superedge::get_caller_decl () const
{
  return get_caller_function ()->decl;
}

/* Given PARM_TO_FIND, a PARM_DECL, identify its index (writing it
   to *OUT if OUT is non-NULL), and return the corresponding argument
   at the callsite.  */

tree
callgraph_superedge::get_arg_for_parm (tree parm_to_find,
				       callsite_expr *out) const
{
  gcc_assert  (TREE_CODE (parm_to_find) == PARM_DECL);

  tree callee = get_callee_decl ();
  const gcall *call_stmt = get_call_stmt ();

  unsigned i = 0;
  for (tree iter_parm = DECL_ARGUMENTS (callee); iter_parm;
       iter_parm = DECL_CHAIN (iter_parm), ++i)
    {
      if (i >= gimple_call_num_args (call_stmt))
	return NULL_TREE;
      if (iter_parm == parm_to_find)
	{
	  if (out)
	    *out = callsite_expr::from_zero_based_param (i);
	  return gimple_call_arg (call_stmt, i);
	}
    }

  /* Not found.  */
  return NULL_TREE;
}

/* Look for a use of ARG_TO_FIND as an argument at this callsite.
   If found, return the default SSA def of the corresponding parm within
   the callee, and if OUT is non-NULL, write the index to *OUT.
   Only the first match is handled.  */

tree
callgraph_superedge::get_parm_for_arg (tree arg_to_find,
				       callsite_expr *out) const
{
  tree callee = get_callee_decl ();
  const gcall *call_stmt = get_call_stmt ();

  unsigned i = 0;
  for (tree iter_parm = DECL_ARGUMENTS (callee); iter_parm;
       iter_parm = DECL_CHAIN (iter_parm), ++i)
    {
      if (i >= gimple_call_num_args (call_stmt))
	return NULL_TREE;
      tree param = gimple_call_arg (call_stmt, i);
      if (arg_to_find == param)
	{
	  if (out)
	    *out = callsite_expr::from_zero_based_param (i);
	  return ssa_default_def (get_callee_function (), iter_parm);
	}
    }

  /* Not found.  */
  return NULL_TREE;
}

/* Map caller_expr back to an expr within the callee, or return NULL_TREE.
   If non-NULL is returned, populate OUT.  */

tree
callgraph_superedge::map_expr_from_caller_to_callee (tree caller_expr,
						     callsite_expr *out) const
{
  /* Is it an argument (actual param)?  If so, convert to
     parameter (formal param).  */
  tree parm = get_parm_for_arg (caller_expr, out);
  if (parm)
    return parm;
  /* Otherwise try return value.  */
  if (caller_expr == gimple_call_lhs (get_call_stmt ()))
    {
      if (out)
	*out = callsite_expr::from_return_value ();
      return DECL_RESULT (get_callee_decl ());
    }

  return NULL_TREE;
}

/* Map callee_expr back to an expr within the caller, or return NULL_TREE.
   If non-NULL is returned, populate OUT.  */

tree
callgraph_superedge::map_expr_from_callee_to_caller (tree callee_expr,
						     callsite_expr *out) const
{
  if (callee_expr == NULL_TREE)
    return NULL_TREE;

  /* If it's a parameter (formal param), get the argument (actual param).  */
  if (TREE_CODE (callee_expr) == PARM_DECL)
    return get_arg_for_parm (callee_expr, out);

  /* Similar for the default SSA name of the PARM_DECL.  */
  if (TREE_CODE (callee_expr) == SSA_NAME
      && SSA_NAME_IS_DEFAULT_DEF (callee_expr)
      && TREE_CODE (SSA_NAME_VAR (callee_expr)) == PARM_DECL)
    return get_arg_for_parm (SSA_NAME_VAR (callee_expr), out);

  /* Otherwise try return value.  */
  if (callee_expr == DECL_RESULT (get_callee_decl ()))
    {
      if (out)
	*out = callsite_expr::from_return_value ();
      return gimple_call_lhs (get_call_stmt ());
    }

  return NULL_TREE;
}

} // namespace ana

#endif /* #if ENABLE_ANALYZER */