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/* Pass computing data for optimizing stdarg functions.

   Copyright (C) 2004, 2005, 2007, 2008, 2009 Free Software Foundation, Inc.

   Contributed by Jakub Jelinek <jakub@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 "tm.h"

#include "tree.h"

#include "function.h"

#include "langhooks.h"

#include "diagnostic.h"

#include "target.h"

#include "tree-flow.h"

#include "tree-pass.h"

#include "tree-stdarg.h"

/* A simple pass that attempts to optimize stdarg functions on architectures

   that need to save register arguments to stack on entry to stdarg functions.

   If the function doesn't use any va_start macros, no registers need to

   be saved.  If va_start macros are used, the va_list variables don't escape

   the function, it is only necessary to save registers that will be used

   in va_arg macros.  E.g. if va_arg is only used with integral types

   in the function, floating point registers don't need to be saved, etc.  */

/* Return true if basic block VA_ARG_BB is dominated by VA_START_BB and

   is executed at most as many times as VA_START_BB.  */

static bool

reachable_at_most_once (basic_block va_arg_bb, basic_block va_start_bb)

{

  VEC (edge, heap) *stack = NULL;

  edge e;

  edge_iterator ei;

  sbitmap visited;

  bool ret;

  if (va_arg_bb == va_start_bb)

    return true;

  if (! dominated_by_p (CDI_DOMINATORS, va_arg_bb, va_start_bb))

    return false;

  visited = sbitmap_alloc (last_basic_block);

  sbitmap_zero (visited);

  ret = true;

  FOR_EACH_EDGE (e, ei, va_arg_bb->preds)

    VEC_safe_push (edge, heap, stack, e);

  while (! VEC_empty (edge, stack))

    {

      basic_block src;

      e = VEC_pop (edge, stack);

      src = e->src;

      if (e->flags & EDGE_COMPLEX)

        {

          ret = false;

          break;

        }

      if (src == va_start_bb)

        continue;

      /* va_arg_bb can be executed more times than va_start_bb.  */

      if (src == va_arg_bb)

        {

          ret = false;

          break;

        }

      gcc_assert (src != ENTRY_BLOCK_PTR);

      if (! TEST_BIT (visited, src->index))

        {

          SET_BIT (visited, src->index);

          FOR_EACH_EDGE (e, ei, src->preds)

            VEC_safe_push (edge, heap, stack, e);

        }

    }

  VEC_free (edge, heap, stack);

  sbitmap_free (visited);

  return ret;

}

/* For statement COUNTER = RHS, if RHS is COUNTER + constant,

   return constant, otherwise return (unsigned HOST_WIDE_INT) -1.

   GPR_P is true if this is GPR counter.  */

static unsigned HOST_WIDE_INT

va_list_counter_bump (struct stdarg_info *si, tree counter, tree rhs,

                      bool gpr_p)

{

  tree lhs, orig_lhs;

  gimple stmt;

  unsigned HOST_WIDE_INT ret = 0, val, counter_val;

  unsigned int max_size;

  if (si->offsets == NULL)

    {

      unsigned int i;

      si->offsets = XNEWVEC (int, num_ssa_names);

      for (i = 0; i < num_ssa_names; ++i)

        si->offsets[i] = -1;

    }

  counter_val = gpr_p ? cfun->va_list_gpr_size : cfun->va_list_fpr_size;

  max_size = gpr_p ? VA_LIST_MAX_GPR_SIZE : VA_LIST_MAX_FPR_SIZE;

  orig_lhs = lhs = rhs;

  while (lhs)

    {

      enum tree_code rhs_code;

      if (si->offsets[SSA_NAME_VERSION (lhs)] != -1)

        {

          if (counter_val >= max_size)

            {

              ret = max_size;

              break;

            }

          ret -= counter_val - si->offsets[SSA_NAME_VERSION (lhs)];

          break;

        }

      stmt = SSA_NAME_DEF_STMT (lhs);

      if (!is_gimple_assign (stmt) || gimple_assign_lhs (stmt) != lhs)

        return (unsigned HOST_WIDE_INT) -1;

      rhs_code = gimple_assign_rhs_code (stmt);

      if ((get_gimple_rhs_class (rhs_code) == GIMPLE_SINGLE_RHS

           || gimple_assign_cast_p (stmt))

          && TREE_CODE (gimple_assign_rhs1 (stmt)) == SSA_NAME)

        {

          lhs = gimple_assign_rhs1 (stmt);

          continue;

        }

      if ((rhs_code == POINTER_PLUS_EXPR

           || rhs_code == PLUS_EXPR)

          && TREE_CODE (gimple_assign_rhs1 (stmt)) == SSA_NAME

          && host_integerp (gimple_assign_rhs2 (stmt), 1))

        {

          ret += tree_low_cst (gimple_assign_rhs2 (stmt), 1);

          lhs = gimple_assign_rhs1 (stmt);

          continue;

        }

      if (get_gimple_rhs_class (rhs_code) != GIMPLE_SINGLE_RHS)

        return (unsigned HOST_WIDE_INT) -1;

      rhs = gimple_assign_rhs1 (stmt);

      if (TREE_CODE (counter) != TREE_CODE (rhs))

        return (unsigned HOST_WIDE_INT) -1;

      if (TREE_CODE (counter) == COMPONENT_REF)

        {

          if (get_base_address (counter) != get_base_address (rhs)

              || TREE_CODE (TREE_OPERAND (rhs, 1)) != FIELD_DECL

              || TREE_OPERAND (counter, 1) != TREE_OPERAND (rhs, 1))

            return (unsigned HOST_WIDE_INT) -1;

        }

      else if (counter != rhs)

        return (unsigned HOST_WIDE_INT) -1;

      lhs = NULL;

    }

  lhs = orig_lhs;

  val = ret + counter_val;

  while (lhs)

    {

      enum tree_code rhs_code;

      if (si->offsets[SSA_NAME_VERSION (lhs)] != -1)

        break;

      if (val >= max_size)

        si->offsets[SSA_NAME_VERSION (lhs)] = max_size;

      else

        si->offsets[SSA_NAME_VERSION (lhs)] = val;

      stmt = SSA_NAME_DEF_STMT (lhs);

      rhs_code = gimple_assign_rhs_code (stmt);

      if ((get_gimple_rhs_class (rhs_code) == GIMPLE_SINGLE_RHS

           || gimple_assign_cast_p (stmt))

          && TREE_CODE (gimple_assign_rhs1 (stmt)) == SSA_NAME)

        {

          lhs = gimple_assign_rhs1 (stmt);

          continue;

        }

      if ((rhs_code == POINTER_PLUS_EXPR

           || rhs_code == PLUS_EXPR)

          && TREE_CODE (gimple_assign_rhs1 (stmt)) == SSA_NAME

          && host_integerp (gimple_assign_rhs2 (stmt), 1))

        {

          val -= tree_low_cst (gimple_assign_rhs2 (stmt), 1);

          lhs = gimple_assign_rhs1 (stmt);

          continue;

        }

      lhs = NULL;

    }

  return ret;

}

/* Called by walk_tree to look for references to va_list variables.  */

static tree

find_va_list_reference (tree *tp, int *walk_subtrees ATTRIBUTE_UNUSED,

                        void *data)

{

  bitmap va_list_vars = (bitmap) ((struct walk_stmt_info *) data)->info;

  tree var = *tp;

  if (TREE_CODE (var) == SSA_NAME)

    var = SSA_NAME_VAR (var);

  if (TREE_CODE (var) == VAR_DECL

      && bitmap_bit_p (va_list_vars, DECL_UID (var)))

    return var;

  return NULL_TREE;

}

/* Helper function of va_list_counter_struct_op.  Compute

   cfun->va_list_{g,f}pr_size.  AP is a va_list GPR/FPR counter,

   if WRITE_P is true, seen in AP = VAR, otherwise seen in VAR = AP

   statement.  GPR_P is true if AP is a GPR counter, false if it is

   a FPR counter.  */

static void

va_list_counter_op (struct stdarg_info *si, tree ap, tree var, bool gpr_p,

                    bool write_p)

{

  unsigned HOST_WIDE_INT increment;

  if (si->compute_sizes < 0)

    {

      si->compute_sizes = 0;

      if (si->va_start_count == 1

          && reachable_at_most_once (si->bb, si->va_start_bb))

        si->compute_sizes = 1;

      if (dump_file && (dump_flags & TDF_DETAILS))

        fprintf (dump_file,

                 "bb%d will %sbe executed at most once for each va_start "

                 "in bb%d\n", si->bb->index, si->compute_sizes ? "" : "not ",

                 si->va_start_bb->index);

    }

  if (write_p

      && si->compute_sizes

      && (increment = va_list_counter_bump (si, ap, var, gpr_p)) + 1 > 1)

    {

      if (gpr_p && cfun->va_list_gpr_size + increment < VA_LIST_MAX_GPR_SIZE)

        {

          cfun->va_list_gpr_size += increment;

          return;

        }

      if (!gpr_p && cfun->va_list_fpr_size + increment < VA_LIST_MAX_FPR_SIZE)

        {

          cfun->va_list_fpr_size += increment;

          return;

        }

    }

  if (write_p || !si->compute_sizes)

    {

      if (gpr_p)

        cfun->va_list_gpr_size = VA_LIST_MAX_GPR_SIZE;

      else

        cfun->va_list_fpr_size = VA_LIST_MAX_FPR_SIZE;

    }

}

/* If AP is a va_list GPR/FPR counter, compute cfun->va_list_{g,f}pr_size.

   If WRITE_P is true, AP has been seen in AP = VAR assignment, if WRITE_P

   is false, AP has been seen in VAR = AP assignment.

   Return true if the AP = VAR (resp. VAR = AP) statement is a recognized

   va_arg operation that doesn't cause the va_list variable to escape

   current function.  */

static bool

va_list_counter_struct_op (struct stdarg_info *si, tree ap, tree var,

                           bool write_p)

{

  tree base;

  if (TREE_CODE (ap) != COMPONENT_REF

      || TREE_CODE (TREE_OPERAND (ap, 1)) != FIELD_DECL)

    return false;

  if (TREE_CODE (var) != SSA_NAME

      || bitmap_bit_p (si->va_list_vars, DECL_UID (SSA_NAME_VAR (var))))

    return false;

  base = get_base_address (ap);

  if (TREE_CODE (base) != VAR_DECL

      || !bitmap_bit_p (si->va_list_vars, DECL_UID (base)))

    return false;

  if (TREE_OPERAND (ap, 1) == va_list_gpr_counter_field)

    va_list_counter_op (si, ap, var, true, write_p);

  else if (TREE_OPERAND (ap, 1) == va_list_fpr_counter_field)

    va_list_counter_op (si, ap, var, false, write_p);

  return true;

}

/* Check for TEM = AP.  Return true if found and the caller shouldn't

   search for va_list references in the statement.  */

static bool

va_list_ptr_read (struct stdarg_info *si, tree ap, tree tem)

{

  if (TREE_CODE (ap) != VAR_DECL

      || !bitmap_bit_p (si->va_list_vars, DECL_UID (ap)))

    return false;

  if (TREE_CODE (tem) != SSA_NAME

      || bitmap_bit_p (si->va_list_vars,

                       DECL_UID (SSA_NAME_VAR (tem)))

      || is_global_var (SSA_NAME_VAR (tem)))

    return false;

  if (si->compute_sizes < 0)

    {

      si->compute_sizes = 0;

      if (si->va_start_count == 1

          && reachable_at_most_once (si->bb, si->va_start_bb))

        si->compute_sizes = 1;

      if (dump_file && (dump_flags & TDF_DETAILS))

        fprintf (dump_file,

                 "bb%d will %sbe executed at most once for each va_start "

                 "in bb%d\n", si->bb->index, si->compute_sizes ? "" : "not ",

                 si->va_start_bb->index);

    }

  /* For void * or char * va_list types, there is just one counter.

     If va_arg is used in a loop, we don't know how many registers need

     saving.  */

  if (! si->compute_sizes)

    return false;

  if (va_list_counter_bump (si, ap, tem, true) == (unsigned HOST_WIDE_INT) -1)

    return false;

  /* Note the temporary, as we need to track whether it doesn't escape

     the current function.  */

  bitmap_set_bit (si->va_list_escape_vars,

                  DECL_UID (SSA_NAME_VAR (tem)));

  return true;

}

/* Check for:

     tem1 = AP;

     TEM2 = tem1 + CST;

     AP = TEM2;

   sequence and update cfun->va_list_gpr_size.  Return true if found.  */

static bool

va_list_ptr_write (struct stdarg_info *si, tree ap, tree tem2)

{

  unsigned HOST_WIDE_INT increment;

  if (TREE_CODE (ap) != VAR_DECL

      || !bitmap_bit_p (si->va_list_vars, DECL_UID (ap)))

    return false;

  if (TREE_CODE (tem2) != SSA_NAME

      || bitmap_bit_p (si->va_list_vars, DECL_UID (SSA_NAME_VAR (tem2))))

    return false;

  if (si->compute_sizes <= 0)

    return false;

  increment = va_list_counter_bump (si, ap, tem2, true);

  if (increment + 1 <= 1)

    return false;

  if (cfun->va_list_gpr_size + increment < VA_LIST_MAX_GPR_SIZE)

    cfun->va_list_gpr_size += increment;

  else

    cfun->va_list_gpr_size = VA_LIST_MAX_GPR_SIZE;

  return true;

}

/* If RHS is X, (some type *) X or X + CST for X a temporary variable

   containing value of some va_list variable plus optionally some constant,

   either set si->va_list_escapes or add LHS to si->va_list_escape_vars,

   depending whether LHS is a function local temporary.  */

static void

check_va_list_escapes (struct stdarg_info *si, tree lhs, tree rhs)

{

  if (! POINTER_TYPE_P (TREE_TYPE (rhs)))

    return;

  if (TREE_CODE (rhs) != SSA_NAME

      || ! bitmap_bit_p (si->va_list_escape_vars,

                         DECL_UID (SSA_NAME_VAR (rhs))))

    return;

  if (TREE_CODE (lhs) != SSA_NAME || is_global_var (SSA_NAME_VAR (lhs)))

    {

      si->va_list_escapes = true;

      return;

    }

  if (si->compute_sizes < 0)

    {

      si->compute_sizes = 0;

      if (si->va_start_count == 1

          && reachable_at_most_once (si->bb, si->va_start_bb))

        si->compute_sizes = 1;

      if (dump_file && (dump_flags & TDF_DETAILS))

        fprintf (dump_file,

                 "bb%d will %sbe executed at most once for each va_start "

                 "in bb%d\n", si->bb->index, si->compute_sizes ? "" : "not ",

                 si->va_start_bb->index);

    }

  /* For void * or char * va_list types, there is just one counter.

     If va_arg is used in a loop, we don't know how many registers need

     saving.  */

  if (! si->compute_sizes)

    {

      si->va_list_escapes = true;

      return;

    }

  if (va_list_counter_bump (si, si->va_start_ap, lhs, true)

      == (unsigned HOST_WIDE_INT) -1)

    {

      si->va_list_escapes = true;

      return;

    }

  bitmap_set_bit (si->va_list_escape_vars,

                  DECL_UID (SSA_NAME_VAR (lhs)));

}

/* Check all uses of temporaries from si->va_list_escape_vars bitmap.

   Return true if va_list might be escaping.  */

static bool

check_all_va_list_escapes (struct stdarg_info *si)

{

  basic_block bb;

  FOR_EACH_BB (bb)

    {

      gimple_stmt_iterator i;

      for (i = gsi_start_bb (bb); !gsi_end_p (i); gsi_next (&i))

        {

          gimple stmt = gsi_stmt (i);

          tree use;

          ssa_op_iter iter;

          if (is_gimple_debug (stmt))

            continue;

          FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_ALL_USES)

            {

              if (! bitmap_bit_p (si->va_list_escape_vars,

                                  DECL_UID (SSA_NAME_VAR (use))))

                continue;

              if (is_gimple_assign (stmt))

                {

                  tree rhs = gimple_assign_rhs1 (stmt);

                  enum tree_code rhs_code = gimple_assign_rhs_code (stmt);

                  /* x = *ap_temp;  */

                  if (gimple_assign_rhs_code (stmt) == INDIRECT_REF

                      && TREE_OPERAND (rhs, 0) == use

                      && TYPE_SIZE_UNIT (TREE_TYPE (rhs))

                      && host_integerp (TYPE_SIZE_UNIT (TREE_TYPE (rhs)), 1)

                      && si->offsets[SSA_NAME_VERSION (use)] != -1)

                    {

                      unsigned HOST_WIDE_INT gpr_size;

                      tree access_size = TYPE_SIZE_UNIT (TREE_TYPE (rhs));

                      gpr_size = si->offsets[SSA_NAME_VERSION (use)]

                                 + tree_low_cst (access_size, 1);

                      if (gpr_size >= VA_LIST_MAX_GPR_SIZE)

                        cfun->va_list_gpr_size = VA_LIST_MAX_GPR_SIZE;

                      else if (gpr_size > cfun->va_list_gpr_size)

                        cfun->va_list_gpr_size = gpr_size;

                      continue;

                    }

                  /* va_arg sequences may contain

                     other_ap_temp = ap_temp;

                     other_ap_temp = ap_temp + constant;

                     other_ap_temp = (some_type *) ap_temp;

                     ap = ap_temp;

                     statements.  */

                  if (rhs == use

                      && ((rhs_code == POINTER_PLUS_EXPR

                           && (TREE_CODE (gimple_assign_rhs2 (stmt))

                               == INTEGER_CST))

                          || gimple_assign_cast_p (stmt)

                          || (get_gimple_rhs_class (rhs_code)

                              == GIMPLE_SINGLE_RHS)))

                    {

                      tree lhs = gimple_assign_lhs (stmt);

                      if (TREE_CODE (lhs) == SSA_NAME

                          && bitmap_bit_p (si->va_list_escape_vars,

                                           DECL_UID (SSA_NAME_VAR (lhs))))

                        continue;

                      if (TREE_CODE (lhs) == VAR_DECL

                          && bitmap_bit_p (si->va_list_vars,

                                           DECL_UID (lhs)))

                        continue;

                    }

                }

              if (dump_file && (dump_flags & TDF_DETAILS))

                {

                  fputs ("va_list escapes in ", dump_file);

                  print_gimple_stmt (dump_file, stmt, 0, dump_flags);

                  fputc ('\n', dump_file);

                }

              return true;

            }

        }

    }

  return false;

}

/* Return true if this optimization pass should be done.

   It makes only sense for stdarg functions.  */

static bool

gate_optimize_stdarg (void)

{

  /* This optimization is only for stdarg functions.  */

  return cfun->stdarg != 0;

}

/* Entry point to the stdarg optimization pass.  */

static unsigned int

execute_optimize_stdarg (void)

{

  basic_block bb;

  bool va_list_escapes = false;

  bool va_list_simple_ptr;

  struct stdarg_info si;

  struct walk_stmt_info wi;

  const char *funcname = NULL;

  tree cfun_va_list;

  cfun->va_list_gpr_size = 0;

  cfun->va_list_fpr_size = 0;

  memset (&si, 0, sizeof (si));

  si.va_list_vars = BITMAP_ALLOC (NULL);

  si.va_list_escape_vars = BITMAP_ALLOC (NULL);

  if (dump_file)

    funcname = lang_hooks.decl_printable_name (current_function_decl, 2);

  cfun_va_list = targetm.fn_abi_va_list (cfun->decl);

  va_list_simple_ptr = POINTER_TYPE_P (cfun_va_list)

                       && (TREE_TYPE (cfun_va_list) == void_type_node

                           || TREE_TYPE (cfun_va_list) == char_type_node);

  gcc_assert (is_gimple_reg_type (cfun_va_list) == va_list_simple_ptr);

  FOR_EACH_BB (bb)

    {

      gimple_stmt_iterator i;

      for (i = gsi_start_bb (bb); !gsi_end_p (i); gsi_next (&i))

        {

          gimple stmt = gsi_stmt (i);

          tree callee, ap;

          if (!is_gimple_call (stmt))

            continue;

          callee = gimple_call_fndecl (stmt);

          if (!callee

              || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL)

            continue;

          switch (DECL_FUNCTION_CODE (callee))

            {

            case BUILT_IN_VA_START:

              break;

              /* If old style builtins are used, don't optimize anything.  */

            case BUILT_IN_SAVEREGS:

            case BUILT_IN_ARGS_INFO:

            case BUILT_IN_NEXT_ARG:

              va_list_escapes = true;

              continue;

            default:

              continue;

            }

          si.va_start_count++;

          ap = gimple_call_arg (stmt, 0);

          if (TREE_CODE (ap) != ADDR_EXPR)

            {

              va_list_escapes = true;

              break;

            }

          ap = TREE_OPERAND (ap, 0);

          if (TREE_CODE (ap) == ARRAY_REF)

            {

              if (! integer_zerop (TREE_OPERAND (ap, 1)))

                {

                  va_list_escapes = true;

                  break;

                }

              ap = TREE_OPERAND (ap, 0);

            }

          if (TYPE_MAIN_VARIANT (TREE_TYPE (ap))

              != TYPE_MAIN_VARIANT (targetm.fn_abi_va_list (cfun->decl))

              || TREE_CODE (ap) != VAR_DECL)

            {

              va_list_escapes = true;

              break;

            }

          if (is_global_var (ap))

            {

              va_list_escapes = true;

              break;

            }

          bitmap_set_bit (si.va_list_vars, DECL_UID (ap));

          /* VA_START_BB and VA_START_AP will be only used if there is just

             one va_start in the function.  */

          si.va_start_bb = bb;

          si.va_start_ap = ap;

        }