Daily bump.

[official-gcc.git] / gcc / tree-inline.c

/* Control and data flow functions for trees.
   Copyright 2001, 2002 Free Software Foundation, Inc.
   Contributed by Alexandre Oliva <aoliva@redhat.com>

This file is part of GNU CC.

GNU CC 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 2, or (at your option)
any later version.

GNU CC 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 GNU CC; see the file COPYING.  If not, write to
the Free Software Foundation, 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */

#include "config.h"
#include "system.h"
#include "toplev.h"
#include "tree.h"
#include "tree-inline.h"
#include "rtl.h"
#include "expr.h"
#include "flags.h"
#include "params.h"
#include "input.h"
#include "insn-config.h"
#include "integrate.h"
#include "varray.h"
#include "hashtab.h"
#include "splay-tree.h"
#include "langhooks.h"

/* This should be eventually be generalized to other languages, but
   this would require a shared function-as-trees infrastructure.  */
#include "c-common.h" 

/* 0 if we should not perform inlining.
   1 if we should expand functions calls inline at the tree level.  
   2 if we should consider *all* functions to be inline 
   candidates.  */

int flag_inline_trees = 0;

/* To Do:

   o In order to make inlining-on-trees work, we pessimized
     function-local static constants.  In particular, they are now
     always output, even when not addressed.  Fix this by treating
     function-local static constants just like global static
     constants; the back-end already knows not to output them if they
     are not needed.

   o Provide heuristics to clamp inlining of recursive template
     calls?  */

/* Data required for function inlining.  */

typedef struct inline_data
{
  /* A stack of the functions we are inlining.  For example, if we are
     compiling `f', which calls `g', which calls `h', and we are
     inlining the body of `h', the stack will contain, `h', followed
     by `g', followed by `f'.  The first few elements of the stack may
     contain other functions that we know we should not recurse into,
     even though they are not directly being inlined.  */
  varray_type fns;
  /* The index of the first element of FNS that really represents an
     inlined function.  */
  unsigned first_inlined_fn;
  /* The label to jump to when a return statement is encountered.  If
     this value is NULL, then return statements will simply be
     remapped as return statements, rather than as jumps.  */
  tree ret_label;
  /* The map from local declarations in the inlined function to
     equivalents in the function into which it is being inlined.  */
  splay_tree decl_map;
  /* Nonzero if we are currently within the cleanup for a
     TARGET_EXPR.  */
  int in_target_cleanup_p;
  /* A stack of the TARGET_EXPRs that we are currently processing.  */
  varray_type target_exprs;
  /* A list of the functions current function has inlined.  */
  varray_type inlined_fns;
  /* The approximate number of statements we have inlined in the
     current call stack.  */
  int inlined_stmts;
  /* We use the same mechanism to build clones that we do to perform
     inlining.  However, there are a few places where we need to
     distinguish between those two situations.  This flag is true if
     we are cloning, rather than inlining.  */
  bool cloning_p;
  /* Hash table used to prevent walk_tree from visiting the same node
     umpteen million times.  */
  htab_t tree_pruner;
} inline_data;

/* Prototypes.  */

static tree initialize_inlined_parameters PARAMS ((inline_data *, tree, tree));
static tree declare_return_variable PARAMS ((inline_data *, tree *));
static tree copy_body_r PARAMS ((tree *, int *, void *));
static tree copy_body PARAMS ((inline_data *));
static tree expand_call_inline PARAMS ((tree *, int *, void *));
static void expand_calls_inline PARAMS ((tree *, inline_data *));
static int inlinable_function_p PARAMS ((tree, inline_data *));
static tree remap_decl PARAMS ((tree, inline_data *));
static void remap_block PARAMS ((tree, tree, inline_data *));
static void copy_scope_stmt PARAMS ((tree *, int *, inline_data *));

/* The approximate number of instructions per statement.  This number
   need not be particularly accurate; it is used only to make
   decisions about when a function is too big to inline.  */
#define INSNS_PER_STMT (10)

/* Remap DECL during the copying of the BLOCK tree for the function.  */

static tree
remap_decl (decl, id)
     tree decl;
     inline_data *id;
{
  splay_tree_node n;
  tree fn;

  /* We only remap local variables in the current function.  */
  fn = VARRAY_TOP_TREE (id->fns);
  if (! (*lang_hooks.tree_inlining.auto_var_in_fn_p) (decl, fn))
    return NULL_TREE;

  /* See if we have remapped this declaration.  */
  n = splay_tree_lookup (id->decl_map, (splay_tree_key) decl);
  /* If we didn't already have an equivalent for this declaration,
     create one now.  */
  if (!n)
    {
      tree t;

      /* Make a copy of the variable or label.  */
      t = copy_decl_for_inlining (decl, fn,
                                  VARRAY_TREE (id->fns, 0));

      /* The decl T could be a dynamic array or other variable size type,
         in which case some fields need to be remapped because they may
         contain SAVE_EXPRs.  */
      if (TREE_TYPE (t) && TREE_CODE (TREE_TYPE (t)) == ARRAY_TYPE
          && TYPE_DOMAIN (TREE_TYPE (t)))
        {
          TREE_TYPE (t) = copy_node (TREE_TYPE (t));
          TYPE_DOMAIN (TREE_TYPE (t))
            = copy_node (TYPE_DOMAIN (TREE_TYPE (t)));
          walk_tree (&TYPE_MAX_VALUE (TYPE_DOMAIN (TREE_TYPE (t))),
                     copy_body_r, id, NULL);
        }

      if (! DECL_NAME (t) && TREE_TYPE (t)
          && (*lang_hooks.tree_inlining.anon_aggr_type_p) (TREE_TYPE (t)))
        {
          /* For a VAR_DECL of anonymous type, we must also copy the
             member VAR_DECLS here and rechain the
             DECL_ANON_UNION_ELEMS.  */
          tree members = NULL;
          tree src;
          
          for (src = DECL_ANON_UNION_ELEMS (t); src;
               src = TREE_CHAIN (src))
            {
              tree member = remap_decl (TREE_VALUE (src), id);

              if (TREE_PURPOSE (src))
                abort ();
              members = tree_cons (NULL, member, members);
            }
          DECL_ANON_UNION_ELEMS (t) = nreverse (members);
        }
      
      /* Remember it, so that if we encounter this local entity
         again we can reuse this copy.  */
      n = splay_tree_insert (id->decl_map,
                             (splay_tree_key) decl,
                             (splay_tree_value) t);
    }

  return (tree) n->value;
}

/* Copy the SCOPE_STMT_BLOCK associated with SCOPE_STMT to contain
   remapped versions of the variables therein.  And hook the new block
   into the block-tree.  If non-NULL, the DECLS are declarations to
   add to use instead of the BLOCK_VARS in the old block.  */

static void
remap_block (scope_stmt, decls, id)
     tree scope_stmt;
     tree decls;
     inline_data *id;
{
  /* We cannot do this in the cleanup for a TARGET_EXPR since we do
     not know whether or not expand_expr will actually write out the
     code we put there.  If it does not, then we'll have more BLOCKs
     than block-notes, and things will go awry.  At some point, we
     should make the back-end handle BLOCK notes in a tidier way,
     without requiring a strict correspondence to the block-tree; then
     this check can go.  */
  if (id->in_target_cleanup_p)
    {
      SCOPE_STMT_BLOCK (scope_stmt) = NULL_TREE;
      return;
    }

  /* If this is the beginning of a scope, remap the associated BLOCK.  */
  if (SCOPE_BEGIN_P (scope_stmt) && SCOPE_STMT_BLOCK (scope_stmt))
    {
      tree old_block;
      tree new_block;
      tree old_var;
      tree fn;

      /* Make the new block.  */
      old_block = SCOPE_STMT_BLOCK (scope_stmt);
      new_block = make_node (BLOCK);
      TREE_USED (new_block) = TREE_USED (old_block);
      BLOCK_ABSTRACT_ORIGIN (new_block) = old_block;
      SCOPE_STMT_BLOCK (scope_stmt) = new_block;

      /* Remap its variables.  */
      for (old_var = decls ? decls : BLOCK_VARS (old_block);
           old_var;
           old_var = TREE_CHAIN (old_var))
        {
          tree new_var;

          /* Remap the variable.  */
          new_var = remap_decl (old_var, id);
          /* If we didn't remap this variable, so we can't mess with
             its TREE_CHAIN.  If we remapped this variable to
             something other than a declaration (say, if we mapped it
             to a constant), then we must similarly omit any mention
             of it here.  */
          if (!new_var || !DECL_P (new_var))
            ;
          else
            {
              TREE_CHAIN (new_var) = BLOCK_VARS (new_block);
              BLOCK_VARS (new_block) = new_var;
            }
        }
      /* We put the BLOCK_VARS in reverse order; fix that now.  */
      BLOCK_VARS (new_block) = nreverse (BLOCK_VARS (new_block));
      fn = VARRAY_TREE (id->fns, 0);
      if (id->cloning_p)
        /* We're building a clone; DECL_INITIAL is still
           error_mark_node, and current_binding_level is the parm
           binding level.  */
        (*lang_hooks.decls.insert_block) (new_block);
      else
        {
          /* Attach this new block after the DECL_INITIAL block for the
             function into which this block is being inlined.  In
             rest_of_compilation we will straighten out the BLOCK tree.  */
          tree *first_block;
          if (DECL_INITIAL (fn))
            first_block = &BLOCK_CHAIN (DECL_INITIAL (fn));
          else
            first_block = &DECL_INITIAL (fn);
          BLOCK_CHAIN (new_block) = *first_block;
          *first_block = new_block;
        }
      /* Remember the remapped block.  */
      splay_tree_insert (id->decl_map,
                         (splay_tree_key) old_block,
                         (splay_tree_value) new_block);
    }
  /* If this is the end of a scope, set the SCOPE_STMT_BLOCK to be the
     remapped block.  */
  else if (SCOPE_END_P (scope_stmt) && SCOPE_STMT_BLOCK (scope_stmt))
    {
      splay_tree_node n;

      /* Find this block in the table of remapped things.  */
      n = splay_tree_lookup (id->decl_map,
                             (splay_tree_key) SCOPE_STMT_BLOCK (scope_stmt));
      if (! n)
        abort ();
      SCOPE_STMT_BLOCK (scope_stmt) = (tree) n->value;
    }
}

/* Copy the SCOPE_STMT pointed to by TP.  */

static void
copy_scope_stmt (tp, walk_subtrees, id)
     tree *tp;
     int *walk_subtrees;
     inline_data *id;
{
  tree block;

  /* Remember whether or not this statement was nullified.  When
     making a copy, copy_tree_r always sets SCOPE_NULLIFIED_P (and
     doesn't copy the SCOPE_STMT_BLOCK) to free callers from having to
     deal with copying BLOCKs if they do not wish to do so.  */
  block = SCOPE_STMT_BLOCK (*tp);
  /* Copy (and replace) the statement.  */
  copy_tree_r (tp, walk_subtrees, NULL);
  /* Restore the SCOPE_STMT_BLOCK.  */
  SCOPE_STMT_BLOCK (*tp) = block;

  /* Remap the associated block.  */
  remap_block (*tp, NULL_TREE, id);
}

/* Called from copy_body via walk_tree.  DATA is really an
   `inline_data *'.  */

static tree
copy_body_r (tp, walk_subtrees, data)
     tree *tp;
     int *walk_subtrees;
     void *data;
{
  inline_data* id;
  tree fn;

  /* Set up.  */
  id = (inline_data *) data;
  fn = VARRAY_TOP_TREE (id->fns);

#if 0
  /* All automatic variables should have a DECL_CONTEXT indicating
     what function they come from.  */
  if ((TREE_CODE (*tp) == VAR_DECL || TREE_CODE (*tp) == LABEL_DECL)
      && DECL_NAMESPACE_SCOPE_P (*tp))
    if (! DECL_EXTERNAL (*tp) && ! TREE_STATIC (*tp))
      abort ();
#endif

  /* If this is a RETURN_STMT, change it into an EXPR_STMT and a
     GOTO_STMT with the RET_LABEL as its target.  */
  if (TREE_CODE (*tp) == RETURN_STMT && id->ret_label)
    {
      tree return_stmt = *tp;
      tree goto_stmt;

      /* Build the GOTO_STMT.  */
      goto_stmt = build_stmt (GOTO_STMT, id->ret_label);
      TREE_CHAIN (goto_stmt) = TREE_CHAIN (return_stmt);
      GOTO_FAKE_P (goto_stmt) = 1;

      /* If we're returning something, just turn that into an
         assignment into the equivalent of the original
         RESULT_DECL.  */
      if (RETURN_EXPR (return_stmt))
        {
          *tp = build_stmt (EXPR_STMT,
                            RETURN_EXPR (return_stmt));
          STMT_IS_FULL_EXPR_P (*tp) = 1;
          /* And then jump to the end of the function.  */
          TREE_CHAIN (*tp) = goto_stmt;
        }
      /* If we're not returning anything just do the jump.  */
      else
        *tp = goto_stmt;
    }
  /* Local variables and labels need to be replaced by equivalent
     variables.  We don't want to copy static variables; there's only
     one of those, no matter how many times we inline the containing
     function.  */
  else if ((*lang_hooks.tree_inlining.auto_var_in_fn_p) (*tp, fn))
    {
      tree new_decl;

      /* Remap the declaration.  */
      new_decl = remap_decl (*tp, id);
      if (! new_decl)
        abort ();
      /* Replace this variable with the copy.  */
      STRIP_TYPE_NOPS (new_decl);
      *tp = new_decl;
    }
#if 0
  else if (nonstatic_local_decl_p (*tp)
           && DECL_CONTEXT (*tp) != VARRAY_TREE (id->fns, 0))
    abort ();
#endif
  else if (TREE_CODE (*tp) == SAVE_EXPR)
    remap_save_expr (tp, id->decl_map, VARRAY_TREE (id->fns, 0),
                     walk_subtrees);
  else if (TREE_CODE (*tp) == UNSAVE_EXPR)
    /* UNSAVE_EXPRs should not be generated until expansion time.  */
    abort ();
  /* For a SCOPE_STMT, we must copy the associated block so that we
     can write out debugging information for the inlined variables.  */
  else if (TREE_CODE (*tp) == SCOPE_STMT && !id->in_target_cleanup_p)
    copy_scope_stmt (tp, walk_subtrees, id);
  /* Otherwise, just copy the node.  Note that copy_tree_r already
     knows not to copy VAR_DECLs, etc., so this is safe.  */
  else
    {
      copy_tree_r (tp, walk_subtrees, NULL);

      /* The copied TARGET_EXPR has never been expanded, even if the
         original node was expanded already.  */
      if (TREE_CODE (*tp) == TARGET_EXPR && TREE_OPERAND (*tp, 3))
        {
          TREE_OPERAND (*tp, 1) = TREE_OPERAND (*tp, 3);
          TREE_OPERAND (*tp, 3) = NULL_TREE;
        }
      else if (TREE_CODE (*tp) == MODIFY_EXPR
               && TREE_OPERAND (*tp, 0) == TREE_OPERAND (*tp, 1)
               && ((*lang_hooks.tree_inlining.auto_var_in_fn_p)
                   (TREE_OPERAND (*tp, 0), fn)))
        {
          /* Some assignments VAR = VAR; don't generate any rtl code
             and thus don't count as variable modification.  Avoid
             keeping bogosities like 0 = 0.  */
          tree decl = TREE_OPERAND (*tp, 0), value;
          splay_tree_node n;

          n = splay_tree_lookup (id->decl_map, (splay_tree_key) decl);
          if (n)
            {
              value = (tree) n->value;
              STRIP_TYPE_NOPS (value);
              if (TREE_CONSTANT (value) || TREE_READONLY_DECL_P (value))
                *tp = value;
            }
        }
    }

  /* Keep iterating.  */
  return NULL_TREE;
}

/* Make a copy of the body of FN so that it can be inserted inline in
   another function.  */

static tree
copy_body (id)
     inline_data *id;
{
  tree body;

  body = DECL_SAVED_TREE (VARRAY_TOP_TREE (id->fns));
  walk_tree (&body, copy_body_r, id, NULL);

  return body;
}

/* Generate code to initialize the parameters of the function at the
   top of the stack in ID from the ARGS (presented as a TREE_LIST).  */

static tree
initialize_inlined_parameters (id, args, fn)
     inline_data *id;
     tree args;
     tree fn;
{
  tree init_stmts;
  tree parms;
  tree a;
  tree p;

  /* Figure out what the parameters are.  */
  parms = DECL_ARGUMENTS (fn);

  /* Start with no initializations whatsoever.  */
  init_stmts = NULL_TREE;

  /* Loop through the parameter declarations, replacing each with an
     equivalent VAR_DECL, appropriately initialized.  */
  for (p = parms, a = args; p;
       a = a ? TREE_CHAIN (a) : a, p = TREE_CHAIN (p))
    {
      tree init_stmt;
      tree var;
      tree value;
      tree cleanup;

      /* Find the initializer.  */
      value = (*lang_hooks.tree_inlining.convert_parm_for_inlining)
              (p, a ? TREE_VALUE (a) : NULL_TREE, fn);

      /* If the parameter is never assigned to, we may not need to
         create a new variable here at all.  Instead, we may be able
         to just use the argument value.  */
      if (TREE_READONLY (p)
          && !TREE_ADDRESSABLE (p)
          && value && !TREE_SIDE_EFFECTS (value))
        {
          /* Simplify the value, if possible.  */
          value = fold (DECL_P (value) ? decl_constant_value (value) : value);

          /* We can't risk substituting complex expressions.  They
             might contain variables that will be assigned to later.
             Theoretically, we could check the expression to see if
             all of the variables that determine its value are
             read-only, but we don't bother.  */
          if (TREE_CONSTANT (value) || TREE_READONLY_DECL_P (value))
            {
              /* If this is a declaration, wrap it a NOP_EXPR so that
                 we don't try to put the VALUE on the list of
                 BLOCK_VARS.  */
              if (DECL_P (value))
                value = build1 (NOP_EXPR, TREE_TYPE (value), value);

              splay_tree_insert (id->decl_map,
                                 (splay_tree_key) p,
                                 (splay_tree_value) value);
              continue;
            }
        }

      /* Make an equivalent VAR_DECL.  */
      var = copy_decl_for_inlining (p, fn, VARRAY_TREE (id->fns, 0));
      /* Register the VAR_DECL as the equivalent for the PARM_DECL;
         that way, when the PARM_DECL is encountered, it will be
         automatically replaced by the VAR_DECL.  */
      splay_tree_insert (id->decl_map,
                         (splay_tree_key) p,
                         (splay_tree_value) var);

      /* Declare this new variable.  */
      init_stmt = build_stmt (DECL_STMT, var);
      TREE_CHAIN (init_stmt) = init_stmts;
      init_stmts = init_stmt;

      /* Initialize this VAR_DECL from the equivalent argument.  If
         the argument is an object, created via a constructor or copy,
         this will not result in an extra copy: the TARGET_EXPR
         representing the argument will be bound to VAR, and the
         object will be constructed in VAR.  */
      if (! TYPE_NEEDS_CONSTRUCTING (TREE_TYPE (p)))
        DECL_INITIAL (var) = value;
      else
        {
          /* Even if P was TREE_READONLY, the new VAR should not be.
             In the original code, we would have constructed a
             temporary, and then the function body would have never
             changed the value of P.  However, now, we will be
             constructing VAR directly.  The constructor body may
             change its value multiple times as it is being
             constructed.  Therefore, it must not be TREE_READONLY;
             the back-end assumes that TREE_READONLY variable is
             assigned to only once.  */
          TREE_READONLY (var) = 0;

          /* Build a run-time initialization.  */
          init_stmt = build_stmt (EXPR_STMT,
                                  build (INIT_EXPR, TREE_TYPE (p),
                                         var, value));
          /* Add this initialization to the list.  Note that we want the
             declaration *after* the initialization because we are going
             to reverse all the initialization statements below.  */
          TREE_CHAIN (init_stmt) = init_stmts;
          init_stmts = init_stmt;
        }

      /* See if we need to clean up the declaration.  */
      cleanup = (*lang_hooks.maybe_build_cleanup) (var);
      if (cleanup) 
        {
          tree cleanup_stmt;
          /* Build the cleanup statement.  */
          cleanup_stmt = build_stmt (CLEANUP_STMT, var, cleanup);
          /* Add it to the *front* of the list; the list will be
             reversed below.  */
          TREE_CHAIN (cleanup_stmt) = init_stmts;
          init_stmts = cleanup_stmt;
        }
    }

  /* Evaluate trailing arguments.  */
  for (; a; a = TREE_CHAIN (a))
    {
      tree init_stmt;
      tree value = TREE_VALUE (a);

      if (! value || ! TREE_SIDE_EFFECTS (value))
        continue;

      init_stmt = build_stmt (EXPR_STMT, value);
      TREE_CHAIN (init_stmt) = init_stmts;
      init_stmts = init_stmt;
    }

  /* The initialization statements have been built up in reverse
     order.  Straighten them out now.  */
  return nreverse (init_stmts);
}

/* Declare a return variable to replace the RESULT_DECL for the
   function we are calling.  An appropriate DECL_STMT is returned.
   The USE_STMT is filled in to contain a use of the declaration to
   indicate the return value of the function.  */

static tree
declare_return_variable (id, use_stmt)
     struct inline_data *id;
     tree *use_stmt;
{
  tree fn = VARRAY_TOP_TREE (id->fns);
  tree result = DECL_RESULT (fn);
  tree var;
  int need_return_decl = 1;

  /* We don't need to do anything for functions that don't return
     anything.  */
  if (!result || VOID_TYPE_P (TREE_TYPE (result)))
    {
      *use_stmt = NULL_TREE;
      return NULL_TREE;
    }

  var = ((*lang_hooks.tree_inlining.copy_res_decl_for_inlining)
         (result, fn, VARRAY_TREE (id->fns, 0), id->decl_map,
          &need_return_decl, &id->target_exprs));

  /* Register the VAR_DECL as the equivalent for the RESULT_DECL; that
     way, when the RESULT_DECL is encountered, it will be
     automatically replaced by the VAR_DECL.  */
  splay_tree_insert (id->decl_map,
                     (splay_tree_key) result,
                     (splay_tree_value) var);

  /* Build the USE_STMT.  If the return type of the function was
     promoted, convert it back to the expected type.  */
  if (TREE_TYPE (var) == TREE_TYPE (TREE_TYPE (fn)))
    *use_stmt = build_stmt (EXPR_STMT, var);
  else
    *use_stmt = build_stmt (EXPR_STMT,
                            build1 (NOP_EXPR, TREE_TYPE (TREE_TYPE (fn)),
                                    var));

  TREE_ADDRESSABLE (*use_stmt) = 1;

  /* Build the declaration statement if FN does not return an
     aggregate.  */
  if (need_return_decl)
    return build_stmt (DECL_STMT, var);
  /* If FN does return an aggregate, there's no need to declare the
     return variable; we're using a variable in our caller's frame.  */
  else
    return NULL_TREE;
}

/* Returns non-zero if a function can be inlined as a tree.  */

int
tree_inlinable_function_p (fn)
     tree fn;
{
  return inlinable_function_p (fn, NULL);
}

/* Returns non-zero if FN is a function that can be inlined into the
   inlining context ID_.  If ID_ is NULL, check whether the function
   can be inlined at all.  */

static int
inlinable_function_p (fn, id)
     tree fn;
     inline_data *id;
{
  int inlinable;

  /* If we've already decided this function shouldn't be inlined,
     there's no need to check again.  */
  if (DECL_UNINLINABLE (fn))
    return 0;

  /* Assume it is not inlinable.  */
  inlinable = 0;

  /* If we're not inlining things, then nothing is inlinable.  */
  if (! flag_inline_trees)
    ;
  /* If we're not inlining all functions and the function was not
     declared `inline', we don't inline it.  Don't think of
     disregarding DECL_INLINE when flag_inline_trees == 2; it's the
     front-end that must set DECL_INLINE in this case, because
     dwarf2out loses if a function is inlined that doesn't have
     DECL_INLINE set.  */
  else if (! DECL_INLINE (fn))
    ;
  /* We can't inline functions that are too big.  Only allow a single
     function to eat up half of our budget.  Make special allowance
     for extern inline functions, though.  */
  else if (! (*lang_hooks.tree_inlining.disregard_inline_limits) (fn)
           && DECL_NUM_STMTS (fn) * INSNS_PER_STMT > MAX_INLINE_INSNS / 2)
    ;
  /* All is well.  We can inline this function.  Traditionally, GCC
     has refused to inline functions using alloca, or functions whose
     values are returned in a PARALLEL, and a few other such obscure
     conditions.  We are not equally constrained at the tree level.  */
  else
    inlinable = 1;

  /* Squirrel away the result so that we don't have to check again.  */
  DECL_UNINLINABLE (fn) = ! inlinable;

  /* Even if this function is not itself too big to inline, it might
     be that we've done so much inlining already that we don't want to
     risk too much inlining any more and thus halve the acceptable
     size.  */
  if (! (*lang_hooks.tree_inlining.disregard_inline_limits) (fn)
      && ((DECL_NUM_STMTS (fn) + (id ? id->inlined_stmts : 0)) * INSNS_PER_STMT
          > MAX_INLINE_INSNS)
      && DECL_NUM_STMTS (fn) * INSNS_PER_STMT > MAX_INLINE_INSNS / 4)
    inlinable = 0;

  if (inlinable && (*lang_hooks.tree_inlining.cannot_inline_tree_fn) (&fn))
    inlinable = 0;
  
  /* If we don't have the function body available, we can't inline
     it.  */
  if (! DECL_SAVED_TREE (fn))
    inlinable = 0;

  /* Check again, language hooks may have modified it.  */
  if (! inlinable || DECL_UNINLINABLE (fn))
    return 0;

  /* Don't do recursive inlining, either.  We don't record this in
     DECL_UNINLINABLE; we may be able to inline this function later.  */
  if (id)
    {
      size_t i;

      for (i = 0; i < VARRAY_ACTIVE_SIZE (id->fns); ++i)
        if (VARRAY_TREE (id->fns, i) == fn)
          return 0;

      if (DECL_INLINED_FNS (fn))
        {
          int j;
          tree inlined_fns = DECL_INLINED_FNS (fn);

          for (j = 0; j < TREE_VEC_LENGTH (inlined_fns); ++j)
            if (TREE_VEC_ELT (inlined_fns, j) == VARRAY_TREE (id->fns, 0))
              return 0;
        }
    }

  /* Return the result.  */
  return inlinable;
}

/* If *TP is a CALL_EXPR, replace it with its inline expansion.  */

static tree
expand_call_inline (tp, walk_subtrees, data)
     tree *tp;
     int *walk_subtrees;
     void *data;
{
  inline_data *id;
  tree t;
  tree expr;
  tree chain;
  tree fn;
  tree scope_stmt;
  tree use_stmt;
  tree arg_inits;
  tree *inlined_body;
  splay_tree st;

  /* See what we've got.  */
  id = (inline_data *) data;
  t = *tp;

  /* Recurse, but letting recursive invocations know that we are
     inside the body of a TARGET_EXPR.  */
  if (TREE_CODE (*tp) == TARGET_EXPR)
    {
      int i, len = first_rtl_op (TARGET_EXPR);

      /* We're walking our own subtrees.  */
      *walk_subtrees = 0;

      /* Push *TP on the stack of pending TARGET_EXPRs.  */
      VARRAY_PUSH_TREE (id->target_exprs, *tp);

      /* Actually walk over them.  This loop is the body of
         walk_trees, omitting the case where the TARGET_EXPR
         itself is handled.  */
      for (i = 0; i < len; ++i)
        {
          if (i == 2)
            ++id->in_target_cleanup_p;
          walk_tree (&TREE_OPERAND (*tp, i), expand_call_inline, data,
                     id->tree_pruner);
          if (i == 2)
            --id->in_target_cleanup_p;
        }

      /* We're done with this TARGET_EXPR now.  */
      VARRAY_POP (id->target_exprs);

      return NULL_TREE;
    }

  if (TYPE_P (t))
    /* Because types were not copied in copy_body, CALL_EXPRs beneath
       them should not be expanded.  This can happen if the type is a
       dynamic array type, for example.  */
    *walk_subtrees = 0;

  /* From here on, we're only interested in CALL_EXPRs.  */
  if (TREE_CODE (t) != CALL_EXPR)
    return NULL_TREE;

  /* First, see if we can figure out what function is being called.
     If we cannot, then there is no hope of inlining the function.  */
  fn = get_callee_fndecl (t);
  if (!fn)
    return NULL_TREE;

  /* If fn is a declaration of a function in a nested scope that was
     globally declared inline, we don't set its DECL_INITIAL.
     However, we can't blindly follow DECL_ABSTRACT_ORIGIN because the
     C++ front-end uses it for cdtors to refer to their internal
     declarations, that are not real functions.  Fortunately those
     don't have trees to be saved, so we can tell by checking their
     DECL_SAVED_TREE.  */
  if (! DECL_INITIAL (fn)
      && DECL_ABSTRACT_ORIGIN (fn)
      && DECL_SAVED_TREE (DECL_ABSTRACT_ORIGIN (fn)))
    fn = DECL_ABSTRACT_ORIGIN (fn);

  /* Don't try to inline functions that are not well-suited to
     inlining.  */
  if (!inlinable_function_p (fn, id))
    return NULL_TREE;

  if (! (*lang_hooks.tree_inlining.start_inlining) (fn))
    return NULL_TREE;

  /* Set the current filename and line number to the function we are
     inlining so that when we create new _STMT nodes here they get
     line numbers corresponding to the function we are calling.  We
     wrap the whole inlined body in an EXPR_WITH_FILE_AND_LINE as well
     because individual statements don't record the filename.  */
  push_srcloc (fn->decl.filename, fn->decl.linenum);

  /* Build a statement-expression containing code to initialize the
     arguments, the actual inline expansion of the body, and a label
     for the return statements within the function to jump to.  The
     type of the statement expression is the return type of the
     function call.  */
  expr = build1 (STMT_EXPR, TREE_TYPE (TREE_TYPE (fn)), NULL_TREE);

  /* Local declarations will be replaced by their equivalents in this
     map.  */
  st = id->decl_map;
  id->decl_map = splay_tree_new (splay_tree_compare_pointers,
                                 NULL, NULL);

  /* Initialize the parameters.  */
  arg_inits = initialize_inlined_parameters (id, TREE_OPERAND (t, 1), fn);
  /* Expand any inlined calls in the initializers.  Do this before we
     push FN on the stack of functions we are inlining; we want to
     inline calls to FN that appear in the initializers for the
     parameters.  */
  expand_calls_inline (&arg_inits, id);
  /* And add them to the tree.  */
  STMT_EXPR_STMT (expr) = chainon (STMT_EXPR_STMT (expr), arg_inits);

  /* Record the function we are about to inline so that we can avoid
     recursing into it.  */
  VARRAY_PUSH_TREE (id->fns, fn);

  /* Record the function we are about to inline if optimize_function
     has not been called on it yet and we don't have it in the list.  */
  if (! DECL_INLINED_FNS (fn))
    {
      int i;

      for (i = VARRAY_ACTIVE_SIZE (id->inlined_fns) - 1; i >= 0; i--)
        if (VARRAY_TREE (id->inlined_fns, i) == fn)
          break;
      if (i < 0)
        VARRAY_PUSH_TREE (id->inlined_fns, fn);
    }

  /* Return statements in the function body will be replaced by jumps
     to the RET_LABEL.  */
  id->ret_label = build_decl (LABEL_DECL, NULL_TREE, NULL_TREE);
  DECL_CONTEXT (id->ret_label) = VARRAY_TREE (id->fns, 0);

  if (! DECL_INITIAL (fn)
      || TREE_CODE (DECL_INITIAL (fn)) != BLOCK)
    abort ();

  /* Create a block to put the parameters in.  We have to do this
     after the parameters have been remapped because remapping
     parameters is different from remapping ordinary variables.  */
  scope_stmt = build_stmt (SCOPE_STMT, DECL_INITIAL (fn));
  SCOPE_BEGIN_P (scope_stmt) = 1;
  SCOPE_NO_CLEANUPS_P (scope_stmt) = 1;
  remap_block (scope_stmt, DECL_ARGUMENTS (fn), id);
  TREE_CHAIN (scope_stmt) = STMT_EXPR_STMT (expr);
  STMT_EXPR_STMT (expr) = scope_stmt;

  /* Tell the debugging backends that this block represents the
     outermost scope of the inlined function.  */
  if (SCOPE_STMT_BLOCK (scope_stmt))
    BLOCK_ABSTRACT_ORIGIN (SCOPE_STMT_BLOCK (scope_stmt)) = DECL_ORIGIN (fn);

  /* Declare the return variable for the function.  */
  STMT_EXPR_STMT (expr)
    = chainon (STMT_EXPR_STMT (expr),
               declare_return_variable (id, &use_stmt));

  /* After we've initialized the parameters, we insert the body of the
     function itself.  */
  inlined_body = &STMT_EXPR_STMT (expr);
  while (*inlined_body)
    inlined_body = &TREE_CHAIN (*inlined_body);
  *inlined_body = copy_body (id);

  /* Close the block for the parameters.  */
  scope_stmt = build_stmt (SCOPE_STMT, DECL_INITIAL (fn));
  SCOPE_NO_CLEANUPS_P (scope_stmt) = 1;
  remap_block (scope_stmt, NULL_TREE, id);
  STMT_EXPR_STMT (expr)
    = chainon (STMT_EXPR_STMT (expr), scope_stmt);

  /* After the body of the function comes the RET_LABEL.  This must come
     before we evaluate the returned value below, because that evalulation
     may cause RTL to be generated.  */
  STMT_EXPR_STMT (expr)
    = chainon (STMT_EXPR_STMT (expr),
               build_stmt (LABEL_STMT, id->ret_label));

  /* Finally, mention the returned value so that the value of the
     statement-expression is the returned value of the function.  */
  STMT_EXPR_STMT (expr) = chainon (STMT_EXPR_STMT (expr), use_stmt);

  /* Clean up.  */
  splay_tree_delete (id->decl_map);
  id->decl_map = st;

  /* The new expression has side-effects if the old one did.  */
  TREE_SIDE_EFFECTS (expr) = TREE_SIDE_EFFECTS (t);

  /* Replace the call by the inlined body.  Wrap it in an
     EXPR_WITH_FILE_LOCATION so that we'll get debugging line notes
     pointing to the right place.  */
  chain = TREE_CHAIN (*tp);
  *tp = build_expr_wfl (expr, DECL_SOURCE_FILE (fn), DECL_SOURCE_LINE (fn),
                        /*col=*/0);
  EXPR_WFL_EMIT_LINE_NOTE (*tp) = 1;
  TREE_CHAIN (*tp) = chain;
  pop_srcloc ();

  /* If the value of the new expression is ignored, that's OK.  We
     don't warn about this for CALL_EXPRs, so we shouldn't warn about
     the equivalent inlined version either.  */
  TREE_USED (*tp) = 1;

  /* Our function now has more statements than it did before.  */
  DECL_NUM_STMTS (VARRAY_TREE (id->fns, 0)) += DECL_NUM_STMTS (fn);
  id->inlined_stmts += DECL_NUM_STMTS (fn);

  /* Recurse into the body of the just inlined function.  */
  expand_calls_inline (inlined_body, id);
  VARRAY_POP (id->fns);

  /* If we've returned to the top level, clear out the record of how
     much inlining has been done.  */
  if (VARRAY_ACTIVE_SIZE (id->fns) == id->first_inlined_fn)
    id->inlined_stmts = 0;

  /* Don't walk into subtrees.  We've already handled them above.  */
  *walk_subtrees = 0;

  (*lang_hooks.tree_inlining.end_inlining) (fn);

  /* Keep iterating.  */
  return NULL_TREE;
}

/* Walk over the entire tree *TP, replacing CALL_EXPRs with inline
   expansions as appropriate.  */

static void
expand_calls_inline (tp, id)
     tree *tp;
     inline_data *id;
{
  /* Search through *TP, replacing all calls to inline functions by
     appropriate equivalents.  Use walk_tree in no-duplicates mode
     to avoid exponential time complexity.  (We can't just use
     walk_tree_without_duplicates, because of the special TARGET_EXPR
     handling in expand_calls.  The hash table is set up in
     optimize_function.  */
  walk_tree (tp, expand_call_inline, id, id->tree_pruner);
}

/* Expand calls to inline functions in the body of FN.  */

void
optimize_inline_calls (fn)
     tree fn;
{
  inline_data id;
  tree prev_fn;
  
  /* Clear out ID.  */
  memset (&id, 0, sizeof (id));

  /* Don't allow recursion into FN.  */
  VARRAY_TREE_INIT (id.fns, 32, "fns");
  VARRAY_PUSH_TREE (id.fns, fn);
  /* Or any functions that aren't finished yet.  */
  prev_fn = NULL_TREE;
  if (current_function_decl)
    {
      VARRAY_PUSH_TREE (id.fns, current_function_decl);
      prev_fn = current_function_decl;
    }

  prev_fn = ((*lang_hooks.tree_inlining.add_pending_fn_decls)
             (&id.fns, prev_fn));
  
  /* Create the stack of TARGET_EXPRs.  */
  VARRAY_TREE_INIT (id.target_exprs, 32, "target_exprs");

  /* Create the list of functions this call will inline.  */
  VARRAY_TREE_INIT (id.inlined_fns, 32, "inlined_fns");

  /* Keep track of the low-water mark, i.e., the point where the first
     real inlining is represented in ID.FNS.  */
  id.first_inlined_fn = VARRAY_ACTIVE_SIZE (id.fns);

  /* Replace all calls to inline functions with the bodies of those
     functions.  */
  id.tree_pruner = htab_create (37, htab_hash_pointer,
                                htab_eq_pointer, NULL);
  expand_calls_inline (&DECL_SAVED_TREE (fn), &id);

  /* Clean up.  */
  htab_delete (id.tree_pruner);
  VARRAY_FREE (id.fns);
  VARRAY_FREE (id.target_exprs);
  if (DECL_LANG_SPECIFIC (fn))
    {
      tree ifn = make_tree_vec (VARRAY_ACTIVE_SIZE (id.inlined_fns));
      
      memcpy (&TREE_VEC_ELT (ifn, 0), &VARRAY_TREE (id.inlined_fns, 0),
              VARRAY_ACTIVE_SIZE (id.inlined_fns) * sizeof (tree));
      DECL_INLINED_FNS (fn) = ifn;
    }
  VARRAY_FREE (id.inlined_fns);
}

/* FN is a function that has a complete body, and CLONE is a function
   whose body is to be set to a copy of FN, mapping argument
   declarations according to the ARG_MAP splay_tree.  */

void
clone_body (clone, fn, arg_map)
     tree clone, fn;
     void *arg_map;
{
  inline_data id;

  /* Clone the body, as if we were making an inline call.  But, remap
     the parameters in the callee to the parameters of caller.  If
     there's an in-charge parameter, map it to an appropriate
     constant.  */
  memset (&id, 0, sizeof (id));
  VARRAY_TREE_INIT (id.fns, 2, "fns");
  VARRAY_PUSH_TREE (id.fns, clone);
  VARRAY_PUSH_TREE (id.fns, fn);
  id.decl_map = (splay_tree)arg_map;

  /* Cloning is treated slightly differently from inlining.  Set
     CLONING_P so that it's clear which operation we're performing.  */
  id.cloning_p = true;

  /* Actually copy the body.  */
  TREE_CHAIN (DECL_SAVED_TREE (clone)) = copy_body (&id);

  /* Clean up.  */
  VARRAY_FREE (id.fns);
}

/* Apply FUNC to all the sub-trees of TP in a pre-order traversal.
   FUNC is called with the DATA and the address of each sub-tree.  If
   FUNC returns a non-NULL value, the traversal is aborted, and the
   value returned by FUNC is returned.  If HTAB is non-NULL it is used
   to record the nodes visited, and to avoid visiting a node more than
   once.  */

tree 
walk_tree (tp, func, data, htab_)
     tree *tp;
     walk_tree_fn func;
     void *data;
     void *htab_;
{
  htab_t htab = (htab_t) htab_;
  enum tree_code code;
  int walk_subtrees;
  tree result;
  
#define WALK_SUBTREE(NODE)                              \
  do                                                    \
    {                                                   \
      result = walk_tree (&(NODE), func, data, htab);   \
      if (result)                                       \
        return result;                                  \
    }                                                   \
  while (0)

#define WALK_SUBTREE_TAIL(NODE)                         \
  do                                                    \
    {                                                   \
       tp = & (NODE);                                   \
       goto tail_recurse;                               \
    }                                                   \
  while (0)

 tail_recurse:
  /* Skip empty subtrees.  */
  if (!*tp)
    return NULL_TREE;

  if (htab)
    {
      void **slot;
      
      /* Don't walk the same tree twice, if the user has requested
         that we avoid doing so.  */
      if (htab_find (htab, *tp))
        return NULL_TREE;
      /* If we haven't already seen this node, add it to the table.  */
      slot = htab_find_slot (htab, *tp, INSERT);
      *slot = *tp;
    }

  /* Call the function.  */
  walk_subtrees = 1;
  result = (*func) (tp, &walk_subtrees, data);

  /* If we found something, return it.  */
  if (result)
    return result;

  code = TREE_CODE (*tp);

  /* Even if we didn't, FUNC may have decided that there was nothing
     interesting below this point in the tree.  */
  if (!walk_subtrees)
    {
      if (statement_code_p (code) || code == TREE_LIST
          || (*lang_hooks.tree_inlining.tree_chain_matters_p) (*tp))
        /* But we still need to check our siblings.  */
        WALK_SUBTREE_TAIL (TREE_CHAIN (*tp));
      else
        return NULL_TREE;
    }

  /* Handle common cases up front.  */
  if (IS_EXPR_CODE_CLASS (TREE_CODE_CLASS (code))
      || TREE_CODE_CLASS (code) == 'r'
      || TREE_CODE_CLASS (code) == 's')
    {
      int i, len;

      /* Set lineno here so we get the right instantiation context
         if we call instantiate_decl from inlinable_function_p.  */
      if (statement_code_p (code) && !STMT_LINENO_FOR_FN_P (*tp))
        lineno = STMT_LINENO (*tp);

      /* Walk over all the sub-trees of this operand.  */
      len = first_rtl_op (code);
      /* TARGET_EXPRs are peculiar: operands 1 and 3 can be the same.
         But, we only want to walk once.  */
      if (code == TARGET_EXPR
          && TREE_OPERAND (*tp, 3) == TREE_OPERAND (*tp, 1))
        --len;
      /* Go through the subtrees.  We need to do this in forward order so
         that the scope of a FOR_EXPR is handled properly.  */
      for (i = 0; i < len; ++i)
        WALK_SUBTREE (TREE_OPERAND (*tp, i));

      /* For statements, we also walk the chain so that we cover the
         entire statement tree.  */
      if (statement_code_p (code))
        {
          if (code == DECL_STMT 
              && DECL_STMT_DECL (*tp) 
              && DECL_P (DECL_STMT_DECL (*tp)))
            {
              /* Walk the DECL_INITIAL and DECL_SIZE.  We don't want to walk
                 into declarations that are just mentioned, rather than
                 declared; they don't really belong to this part of the tree.
                 And, we can see cycles: the initializer for a declaration can
                 refer to the declaration itself.  */
              WALK_SUBTREE (DECL_INITIAL (DECL_STMT_DECL (*tp)));
              WALK_SUBTREE (DECL_SIZE (DECL_STMT_DECL (*tp)));
              WALK_SUBTREE (DECL_SIZE_UNIT (DECL_STMT_DECL (*tp)));
            }

          /* This can be tail-recursion optimized if we write it this way.  */
          WALK_SUBTREE_TAIL (TREE_CHAIN (*tp));
        }

      /* We didn't find what we were looking for.  */
      return NULL_TREE;
    }
  else if (TREE_CODE_CLASS (code) == 'd')
    {
      WALK_SUBTREE_TAIL (TREE_TYPE (*tp));
    }

  result = (*lang_hooks.tree_inlining.walk_subtrees) (tp, &walk_subtrees, func,
                                                      data, htab);
  if (result || ! walk_subtrees)
    return result;

  /* Not one of the easy cases.  We must explicitly go through the
     children.  */
  switch (code)
    {
    case ERROR_MARK:
    case IDENTIFIER_NODE:
    case INTEGER_CST:
    case REAL_CST:
    case VECTOR_CST:
    case STRING_CST:
    case REAL_TYPE:
    case COMPLEX_TYPE:
    case VECTOR_TYPE:
    case VOID_TYPE:
    case BOOLEAN_TYPE:
    case UNION_TYPE:
    case ENUMERAL_TYPE:
    case BLOCK:
    case RECORD_TYPE:
      /* None of thse have subtrees other than those already walked
         above.  */
      break;

    case POINTER_TYPE:
    case REFERENCE_TYPE:
      WALK_SUBTREE_TAIL (TREE_TYPE (*tp));
      break;

    case TREE_LIST:
      WALK_SUBTREE (TREE_VALUE (*tp));
      WALK_SUBTREE_TAIL (TREE_CHAIN (*tp));
      break;

    case TREE_VEC:
      {
        int len = TREE_VEC_LENGTH (*tp);

        if (len == 0)
          break;

        /* Walk all elements but the first.  */
        while (--len)
          WALK_SUBTREE (TREE_VEC_ELT (*tp, len));

        /* Now walk the first one as a tail call.  */
        WALK_SUBTREE_TAIL (TREE_VEC_ELT (*tp, 0));
      }

    case COMPLEX_CST:
      WALK_SUBTREE (TREE_REALPART (*tp));
      WALK_SUBTREE_TAIL (TREE_IMAGPART (*tp));

    case CONSTRUCTOR:
      WALK_SUBTREE_TAIL (CONSTRUCTOR_ELTS (*tp));

    case METHOD_TYPE:
      WALK_SUBTREE (TYPE_METHOD_BASETYPE (*tp));
      /* Fall through.  */

    case FUNCTION_TYPE:
      WALK_SUBTREE (TREE_TYPE (*tp));
      {
        tree arg = TYPE_ARG_TYPES (*tp);

        /* We never want to walk into default arguments.  */
        for (; arg; arg = TREE_CHAIN (arg))
          WALK_SUBTREE (TREE_VALUE (arg));
      }
      break;

    case ARRAY_TYPE:
      WALK_SUBTREE (TREE_TYPE (*tp));
      WALK_SUBTREE_TAIL (TYPE_DOMAIN (*tp));

    case INTEGER_TYPE:
      WALK_SUBTREE (TYPE_MIN_VALUE (*tp));
      WALK_SUBTREE_TAIL (TYPE_MAX_VALUE (*tp));

    case OFFSET_TYPE:
      WALK_SUBTREE (TREE_TYPE (*tp));
      WALK_SUBTREE_TAIL (TYPE_OFFSET_BASETYPE (*tp));

    default:
      abort ();
    }

  /* We didn't find what we were looking for.  */
  return NULL_TREE;

#undef WALK_SUBTREE
}

/* Like walk_tree, but does not walk duplicate nodes more than 
   once.  */

tree 
walk_tree_without_duplicates (tp, func, data)
     tree *tp;
     walk_tree_fn func;
     void *data;
{
  tree result;
  htab_t htab;

  htab = htab_create (37, htab_hash_pointer, htab_eq_pointer, NULL);
  result = walk_tree (tp, func, data, htab);
  htab_delete (htab);
  return result;
}

/* Passed to walk_tree.  Copies the node pointed to, if appropriate.  */

tree
copy_tree_r (tp, walk_subtrees, data)
     tree *tp;
     int *walk_subtrees;
     void *data ATTRIBUTE_UNUSED;
{
  enum tree_code code = TREE_CODE (*tp);

  /* We make copies of most nodes.  */
  if (IS_EXPR_CODE_CLASS (TREE_CODE_CLASS (code))
      || TREE_CODE_CLASS (code) == 'r'
      || TREE_CODE_CLASS (code) == 'c'
      || TREE_CODE_CLASS (code) == 's'
      || code == TREE_LIST
      || code == TREE_VEC
      || (*lang_hooks.tree_inlining.tree_chain_matters_p) (*tp))
    {
      /* Because the chain gets clobbered when we make a copy, we save it
         here.  */
      tree chain = TREE_CHAIN (*tp);

      /* Copy the node.  */
      *tp = copy_node (*tp);

      /* Now, restore the chain, if appropriate.  That will cause
         walk_tree to walk into the chain as well.  */
      if (code == PARM_DECL || code == TREE_LIST
          || (*lang_hooks.tree_inlining.tree_chain_matters_p) (*tp)
          || statement_code_p (code))
        TREE_CHAIN (*tp) = chain;

      /* For now, we don't update BLOCKs when we make copies.  So, we
         have to nullify all scope-statements.  */
      if (TREE_CODE (*tp) == SCOPE_STMT)
        SCOPE_STMT_BLOCK (*tp) = NULL_TREE;
    }
  else if (TREE_CODE_CLASS (code) == 't')
    /* There's no need to copy types, or anything beneath them.  */
    *walk_subtrees = 0;

  return NULL_TREE;
}

/* The SAVE_EXPR pointed to by TP is being copied.  If ST contains
   information indicating to what new SAVE_EXPR this one should be
   mapped, use that one.  Otherwise, create a new node and enter it in
   ST.  FN is the function into which the copy will be placed.  */

void
remap_save_expr (tp, st_, fn, walk_subtrees)
     tree *tp;
     void *st_;
     tree fn;
     int *walk_subtrees;
{
  splay_tree st = (splay_tree) st_;
  splay_tree_node n;

  /* See if we already encountered this SAVE_EXPR.  */
  n = splay_tree_lookup (st, (splay_tree_key) *tp);
      
  /* If we didn't already remap this SAVE_EXPR, do so now.  */
  if (!n)
    {
      tree t = copy_node (*tp);

      /* The SAVE_EXPR is now part of the function into which we
         are inlining this body.  */
      SAVE_EXPR_CONTEXT (t) = fn;
      /* And we haven't evaluated it yet.  */
      SAVE_EXPR_RTL (t) = NULL_RTX;
      /* Remember this SAVE_EXPR.  */
      n = splay_tree_insert (st,
                             (splay_tree_key) *tp,
                             (splay_tree_value) t);
      /* Make sure we don't remap an already-remapped SAVE_EXPR.  */
      splay_tree_insert (st, (splay_tree_key) t,
                         (splay_tree_value) error_mark_node);
    }
  else
    /* We've already walked into this SAVE_EXPR, so we needn't do it
       again.  */
    *walk_subtrees = 0;

  /* Replace this SAVE_EXPR with the copy.  */
  *tp = (tree) n->value;
}