Drop overflow from constants while building ranges in ranger.

[thirdparty/gcc.git] / gcc / gimple-range.cc

/* Code for GIMPLE range related routines.
   Copyright (C) 2019-2020 Free Software Foundation, Inc.
   Contributed by Andrew MacLeod <amacleod@redhat.com>
   and Aldy Hernandez <aldyh@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 "backend.h"
#include "insn-codes.h"
#include "rtl.h"
#include "tree.h"
#include "gimple.h"
#include "ssa.h"
#include "gimple-pretty-print.h"
#include "gimple-iterator.h"
#include "optabs-tree.h"
#include "gimple-fold.h"
#include "tree-cfg.h"
#include "fold-const.h"
#include "tree-cfg.h"
#include "wide-int.h"
#include "fold-const.h"
#include "case-cfn-macros.h"
#include "omp-general.h"
#include "cfgloop.h"
#include "tree-ssa-loop.h"
#include "tree-scalar-evolution.h"
#include "dbgcnt.h"
#include "alloc-pool.h"
#include "vr-values.h"
#include "gimple-range.h"


// Adjust the range for a pointer difference where the operands came
// from a memchr.
//
// This notices the following sequence:
//
//      def = __builtin_memchr (arg, 0, sz)
//      n = def - arg
//
// The range for N can be narrowed to [0, PTRDIFF_MAX - 1].

static void
adjust_pointer_diff_expr (irange &res, const gimple *diff_stmt)
{
  tree op0 = gimple_assign_rhs1 (diff_stmt);
  tree op1 = gimple_assign_rhs2 (diff_stmt);
  tree op0_ptype = TREE_TYPE (TREE_TYPE (op0));
  tree op1_ptype = TREE_TYPE (TREE_TYPE (op1));
  gimple *call;

  if (TREE_CODE (op0) == SSA_NAME
      && TREE_CODE (op1) == SSA_NAME
      && (call = SSA_NAME_DEF_STMT (op0))
      && is_gimple_call (call)
      && gimple_call_builtin_p (call, BUILT_IN_MEMCHR)
      && TYPE_MODE (op0_ptype) == TYPE_MODE (char_type_node)
      && TYPE_PRECISION (op0_ptype) == TYPE_PRECISION (char_type_node)
      && TYPE_MODE (op1_ptype) == TYPE_MODE (char_type_node)
      && TYPE_PRECISION (op1_ptype) == TYPE_PRECISION (char_type_node)
      && gimple_call_builtin_p (call, BUILT_IN_MEMCHR)
      && vrp_operand_equal_p (op1, gimple_call_arg (call, 0))
      && integer_zerop (gimple_call_arg (call, 1)))
    {
      tree max = vrp_val_max (ptrdiff_type_node);
      wide_int wmax = wi::to_wide (max, TYPE_PRECISION (TREE_TYPE (max)));
      tree expr_type = gimple_expr_type (diff_stmt);
      tree range_min = build_zero_cst (expr_type);
      tree range_max = wide_int_to_tree (expr_type, wmax - 1);
      int_range<2> r (range_min, range_max);
      res.intersect (r);
    }
}

// This function looks for situations when walking the use/def chains
// may provide additonal contextual range information not exposed on
// this statement.  Like knowing the IMAGPART return value from a
// builtin function is a boolean result.

// We should rework how we're called, as we have an op_unknown entry
// for IMAGPART_EXPR and POINTER_DIFF_EXPR in range-ops just so this
// function gets called.

static void
gimple_range_adjustment (irange &res, const gimple *stmt)
{
  switch (gimple_expr_code (stmt))
    {
    case POINTER_DIFF_EXPR:
      adjust_pointer_diff_expr (res, stmt);
      return;

    case IMAGPART_EXPR:
      {
        tree name = TREE_OPERAND (gimple_assign_rhs1 (stmt), 0);
        if (TREE_CODE (name) == SSA_NAME)
          {
            gimple *def_stmt = SSA_NAME_DEF_STMT (name);
            if (def_stmt && is_gimple_call (def_stmt)
                && gimple_call_internal_p (def_stmt))
              {
                switch (gimple_call_internal_fn (def_stmt))
                  {
                  case IFN_ADD_OVERFLOW:
                  case IFN_SUB_OVERFLOW:
                  case IFN_MUL_OVERFLOW:
                  case IFN_ATOMIC_COMPARE_EXCHANGE:
                    {
                      int_range<2> r;
                      r.set_varying (boolean_type_node);
                      tree type = TREE_TYPE (gimple_assign_lhs (stmt));
                      range_cast (r, type);
                      res.intersect (r);
                    }
                  default:
                    break;
                  }
              }
          }
        break;
      }

    default:
      break;
    }
}

// Return a range in R for the tree EXPR.  Return true if a range is
// representable, and UNDEFINED/false if not.

bool
get_tree_range (irange &r, tree expr)
{
  tree type;
  if (TYPE_P (expr))
    type = expr;
  else
    type = TREE_TYPE (expr);

  // Return false if the type isn't suported.
  if (!irange::supports_type_p (type))
    {
      r.set_undefined ();
      return false;
    }

  switch (TREE_CODE (expr))
    {
      case INTEGER_CST:
        if (TREE_OVERFLOW_P (expr))
          expr = drop_tree_overflow (expr);
        r.set (expr, expr);
        return true;

      case SSA_NAME:
        r = gimple_range_global (expr);
        return true;

      case ADDR_EXPR:
        {
          // Handle &var which can show up in phi arguments.
          bool ov;
          if (tree_single_nonzero_warnv_p (expr, &ov))
            {
              r = range_nonzero (type);
              return true;
            }
          break;
        }

      default:
        break;
    }
  r.set_varying (type);
  return true;
}

// Fold this unary statement using R1 as operand1's range, returning
// the result in RES.  Return false if the operation fails.

bool
gimple_range_fold (irange &res, const gimple *stmt, const irange &r1)
{
  gcc_checking_assert (gimple_range_handler (stmt));

  tree type = gimple_expr_type (stmt);
  // Unary SSA operations require the LHS type as the second range.
  int_range<2> r2 (type);

  return gimple_range_fold (res, stmt, r1, r2);
}

// Fold this binary statement using R1 and R2 as the operands ranges,
// returning the result in RES.  Return false if the operation fails.

bool
gimple_range_fold (irange &res, const gimple *stmt,
                   const irange &r1, const irange &r2)
{
  gcc_checking_assert (gimple_range_handler (stmt));

  gimple_range_handler (stmt)->fold_range (res, gimple_expr_type (stmt),
                                           r1, r2);

  // If there are any gimple lookups, do those now.
  gimple_range_adjustment (res, stmt);
  return true;
}

// Return the base of the RHS of an assignment.

tree
gimple_range_base_of_assignment (const gimple *stmt)
{
  gcc_checking_assert (gimple_code (stmt) == GIMPLE_ASSIGN);
  tree op1 = gimple_assign_rhs1 (stmt);
  if (gimple_assign_rhs_code (stmt) == ADDR_EXPR)
    return get_base_address (TREE_OPERAND (op1, 0));
  return op1;
}

// Return the first operand of this statement if it is a valid operand
// supported by ranges, otherwise return NULL_TREE.  Special case is
// &(SSA_NAME expr), return the SSA_NAME instead of the ADDR expr.

tree
gimple_range_operand1 (const gimple *stmt)
{
  gcc_checking_assert (gimple_range_handler (stmt));

  switch (gimple_code (stmt))
    {
      case GIMPLE_COND:
        return gimple_cond_lhs (stmt);
      case GIMPLE_ASSIGN:
        {
          tree base = gimple_range_base_of_assignment (stmt);
          if (base && TREE_CODE (base) == MEM_REF)
            {
              // If the base address is an SSA_NAME, we return it
              // here.  This allows processing of the range of that
              // name, while the rest of the expression is simply
              // ignored.  The code in range_ops will see the
              // ADDR_EXPR and do the right thing.
              tree ssa = TREE_OPERAND (base, 0);
              if (TREE_CODE (ssa) == SSA_NAME)
                return ssa;
            }
          return base;
        }
      default:
        break;
    }
  return NULL;
}

// Return the second operand of statement STMT, otherwise return NULL_TREE.

tree
gimple_range_operand2 (const gimple *stmt)
{
  gcc_checking_assert (gimple_range_handler (stmt));

  switch (gimple_code (stmt))
    {
    case GIMPLE_COND:
      return gimple_cond_rhs (stmt);
    case GIMPLE_ASSIGN:
      if (gimple_num_ops (stmt) >= 3)
        return gimple_assign_rhs2 (stmt);
    default:
      break;
    }
  return NULL_TREE;
}

// Calculate what we can determine of the range of this unary
// statement's operand if the lhs of the expression has the range
// LHS_RANGE.  Return false if nothing can be determined.

bool
gimple_range_calc_op1 (irange &r, const gimple *stmt, const irange &lhs_range)
{
  gcc_checking_assert (gimple_num_ops (stmt) < 3);

  // An empty range is viral.
  tree type = TREE_TYPE (gimple_range_operand1 (stmt));
  if (lhs_range.undefined_p ())
    {
      r.set_undefined ();
      return true;
    }
  // Unary operations require the type of the first operand in the
  // second range position.
  int_range<2> type_range (type);
  return gimple_range_handler (stmt)->op1_range (r, type, lhs_range,
                                                 type_range);
}

// Calculate what we can determine of the range of this statement's
// first operand if the lhs of the expression has the range LHS_RANGE
// and the second operand has the range OP2_RANGE.  Return false if
// nothing can be determined.

bool
gimple_range_calc_op1 (irange &r, const gimple *stmt,
                       const irange &lhs_range, const irange &op2_range)
{
  // Unary operation are allowed to pass a range in for second operand
  // as there are often additional restrictions beyond the type which
  // can be imposed.  See operator_cast::op1_range().
  tree type = TREE_TYPE (gimple_range_operand1 (stmt));
  // An empty range is viral.
  if (op2_range.undefined_p () || lhs_range.undefined_p ())
    {
      r.set_undefined ();
      return true;
    }
  return gimple_range_handler (stmt)->op1_range (r, type, lhs_range,
                                                 op2_range);
}

// Calculate what we can determine of the range of this statement's
// second operand if the lhs of the expression has the range LHS_RANGE
// and the first operand has the range OP1_RANGE.  Return false if
// nothing can be determined.

bool
gimple_range_calc_op2 (irange &r, const gimple *stmt,
                       const irange &lhs_range, const irange &op1_range)
{
  tree type = TREE_TYPE (gimple_range_operand2 (stmt));
  // An empty range is viral.
  if (op1_range.undefined_p () || lhs_range.undefined_p ())
    {
      r.set_undefined ();
      return true;
    }
  return gimple_range_handler (stmt)->op2_range (r, type, lhs_range,
                                                 op1_range);
}

// Calculate a range for statement S and return it in R. If NAME is provided it
// represents the SSA_NAME on the LHS of the statement. It is only required
// if there is more than one lhs/output.  If a range cannot
// be calculated, return false.

bool
gimple_ranger::calc_stmt (irange &r, gimple *s, tree name)
{
  bool res = false;
  // If name is specified, make sure it is an LHS of S.
  gcc_checking_assert (name ? SSA_NAME_DEF_STMT (name) == s : true);

  if (gimple_range_handler (s))
    res = range_of_range_op (r, s);
  else if (is_a<gphi *>(s))
    res = range_of_phi (r, as_a<gphi *> (s));
  else if (is_a<gcall *>(s))
    res = range_of_call (r, as_a<gcall *> (s));
  else if (is_a<gassign *> (s) && gimple_assign_rhs_code (s) == COND_EXPR)
    res = range_of_cond_expr (r, as_a<gassign *> (s));

  if (!res)
    {
      // If no name is specified, try the expression kind.
      if (!name)
        {
          tree t = gimple_expr_type (s);
          if (!irange::supports_type_p (t))
            return false;
          r.set_varying (t);
          return true;
        }
      if (!gimple_range_ssa_p (name))
        return false;
      // We don't understand the stmt, so return the global range.
      r = gimple_range_global (name);
      return true;
    }

  if (r.undefined_p ())
    return true;

  // We sometimes get compatible types copied from operands, make sure
  // the correct type is being returned.
  if (name && TREE_TYPE (name) != r.type ())
    {
      gcc_checking_assert (range_compatible_p (r.type (), TREE_TYPE (name)));
      range_cast (r, TREE_TYPE (name));
    }
  return true;
}

// Calculate a range for range_op statement S and return it in R.  If any
// If a range cannot be calculated, return false.

bool
gimple_ranger::range_of_range_op (irange &r, gimple *s)
{
  int_range_max range1, range2;
  tree lhs = gimple_get_lhs (s);
  tree type = gimple_expr_type (s);
  gcc_checking_assert (irange::supports_type_p (type));

  tree op1 = gimple_range_operand1 (s);
  tree op2 = gimple_range_operand2 (s);

  if (lhs)
    {
      // Register potential dependencies for stale value tracking.
      m_cache.register_dependency (lhs, op1);
      m_cache.register_dependency (lhs, op2);
    }

  if (range_of_non_trivial_assignment (r, s))
    return true;

  if (range_of_expr (range1, op1, s))
    {
      if (!op2)
        return gimple_range_fold (r, s, range1);

      if (range_of_expr (range2, op2, s))
        return gimple_range_fold (r, s, range1, range2);
    }
  r.set_varying (type);
  return true;
}

// Calculate the range of a non-trivial assignment.  That is, is one
// inolving arithmetic on an SSA name (for example, an ADDR_EXPR).
// Return the range in R.
//
// If a range cannot be calculated, return false.

bool
gimple_ranger::range_of_non_trivial_assignment (irange &r, gimple *stmt)
{
  if (gimple_code (stmt) != GIMPLE_ASSIGN)
    return false;

  tree base = gimple_range_base_of_assignment (stmt);
  if (base)
    {
      if (TREE_CODE (base) == MEM_REF)
        {
          if (TREE_CODE (TREE_OPERAND (base, 0)) == SSA_NAME)
            {
              int_range_max range1;
              tree ssa = TREE_OPERAND (base, 0);
              if (range_of_expr (range1, ssa, stmt))
                {
                  tree type = TREE_TYPE (ssa);
                  range_operator *op = range_op_handler (POINTER_PLUS_EXPR,
                                                         type);
                  int_range<2> offset (TREE_OPERAND (base, 1),
                                       TREE_OPERAND (base, 1));
                  op->fold_range (r, type, range1, offset);
                  return true;
                }
            }
          return false;
        }
      if (gimple_assign_rhs_code (stmt) == ADDR_EXPR)
        {
          // Handle "= &a"  and return non-zero.
          r = range_nonzero (TREE_TYPE (gimple_assign_rhs1 (stmt)));
          return true;
        }
    }
  return false;
}

// Calculate a range for phi statement S and return it in R.
// If a range cannot be calculated, return false.

bool
gimple_ranger::range_of_phi (irange &r, gphi *phi)
{
  tree phi_def = gimple_phi_result (phi);
  tree type = TREE_TYPE (phi_def);
  int_range_max arg_range;
  unsigned x;

  if (!irange::supports_type_p (type))
    return false;

  // Start with an empty range, unioning in each argument's range.
  r.set_undefined ();
  for (x = 0; x < gimple_phi_num_args (phi); x++)
    {
      tree arg = gimple_phi_arg_def (phi, x);
      edge e = gimple_phi_arg_edge (phi, x);

      // Register potential dependencies for stale value tracking.
      m_cache.register_dependency (phi_def, arg);

      range_on_edge (arg_range, e, arg);
      r.union_ (arg_range);
      // Once the value reaches varying, stop looking.
      if (r.varying_p ())
        break;
    }

  // If SCEV is available, query if this PHI has any knonwn values.
  if (scev_initialized_p () && !POINTER_TYPE_P (TREE_TYPE (phi_def)))
    {
      value_range loop_range;
      class loop *l = loop_containing_stmt (phi);
      if (l && loop_outer (l))
        {
          range_of_ssa_name_with_loop_info (loop_range, phi_def, l, phi);
          if (!loop_range.varying_p ())
            {
              if (dump_file && (dump_flags & TDF_DETAILS))
                {
                  fprintf (dump_file, "   Loops range found for ");
                  print_generic_expr (dump_file, phi_def, TDF_SLIM);
                  fprintf (dump_file, ": ");
                  loop_range.dump (dump_file);
                  fprintf (dump_file, " and calculated range :");
                  r.dump (dump_file);
                  fprintf (dump_file, "\n");
                }
              r.intersect (loop_range);
            }
        }
    }

  return true;
}

// Calculate a range for call statement S and return it in R.
// If a range cannot be calculated, return false.

bool
gimple_ranger::range_of_call (irange &r, gcall *call)
{
  tree type = gimple_call_return_type (call);
  tree lhs = gimple_call_lhs (call);
  bool strict_overflow_p;

  if (!irange::supports_type_p (type))
    return false;

  if (range_of_builtin_call (r, call))
    ;
  else if (gimple_stmt_nonnegative_warnv_p (call, &strict_overflow_p))
    r.set (build_int_cst (type, 0), TYPE_MAX_VALUE (type));
  else if (gimple_call_nonnull_result_p (call)
           || gimple_call_nonnull_arg (call))
    r = range_nonzero (type);
  else
    r.set_varying (type);

  // If there is an LHS, intersect that with what is known.
  if (lhs)
    {
      value_range def;
      def = gimple_range_global (lhs);
      r.intersect (def);
    }
  return true;
}

// Return the range of a __builtin_ubsan* in CALL and set it in R.
// CODE is the type of ubsan call (PLUS_EXPR, MINUS_EXPR or
// MULT_EXPR).

static void
range_of_builtin_ubsan_call (range_query &query, irange &r, gcall *call,
                             tree_code code)
{
  gcc_checking_assert (code == PLUS_EXPR || code == MINUS_EXPR
                       || code == MULT_EXPR);
  tree type = gimple_call_return_type (call);
  range_operator *op = range_op_handler (code, type);
  gcc_checking_assert (op);
  int_range_max ir0, ir1;
  tree arg0 = gimple_call_arg (call, 0);
  tree arg1 = gimple_call_arg (call, 1);
  query.range_of_expr (ir0, arg0, call);
  query.range_of_expr (ir1, arg1, call);

  bool saved_flag_wrapv = flag_wrapv;
  // Pretend the arithmetic is wrapping.  If there is any overflow,
  // we'll complain, but will actually do wrapping operation.
  flag_wrapv = 1;
  op->fold_range (r, type, ir0, ir1);
  flag_wrapv = saved_flag_wrapv;

  // If for both arguments vrp_valueize returned non-NULL, this should
  // have been already folded and if not, it wasn't folded because of
  // overflow.  Avoid removing the UBSAN_CHECK_* calls in that case.
  if (r.singleton_p ())
    r.set_varying (type);
}

// For a builtin in CALL, return a range in R if known and return
// TRUE.  Otherwise return FALSE.

bool
range_of_builtin_call (range_query &query, irange &r, gcall *call)
{
  combined_fn func = gimple_call_combined_fn (call);
  if (func == CFN_LAST)
    return false;

  tree type = gimple_call_return_type (call);
  tree arg;
  int mini, maxi, zerov = 0, prec;
  scalar_int_mode mode;

  switch (func)
    {
    case CFN_BUILT_IN_CONSTANT_P:
      if (cfun->after_inlining)
        {
          r.set_zero (type);
          // r.equiv_clear ();
          return true;
        }
      arg = gimple_call_arg (call, 0);
      if (query.range_of_expr (r, arg, call) && r.singleton_p ())
        {
          r.set (build_one_cst (type), build_one_cst (type));
          return true;
        }
      break;

    CASE_CFN_FFS:
    CASE_CFN_POPCOUNT:
      // __builtin_ffs* and __builtin_popcount* return [0, prec].
      arg = gimple_call_arg (call, 0);
      prec = TYPE_PRECISION (TREE_TYPE (arg));
      mini = 0;
      maxi = prec;
      query.range_of_expr (r, arg, call);
      // If arg is non-zero, then ffs or popcount are non-zero.
      if (!range_includes_zero_p (&r))
        mini = 1;
      // If some high bits are known to be zero, decrease the maximum.
      if (!r.undefined_p ())
        {
          if (TYPE_SIGN (r.type ()) == SIGNED)
            range_cast (r, unsigned_type_for (r.type ()));
          wide_int max = r.upper_bound ();
          maxi = wi::floor_log2 (max) + 1;
        }
      r.set (build_int_cst (type, mini), build_int_cst (type, maxi));
      return true;

    CASE_CFN_PARITY:
      r.set (build_zero_cst (type), build_one_cst (type));
      return true;

    CASE_CFN_CLZ:
      // __builtin_c[lt]z* return [0, prec-1], except when the
      // argument is 0, but that is undefined behavior.
      //
      // For __builtin_c[lt]z* consider argument of 0 always undefined
      // behavior, for internal fns depending on C?Z_DEFINED_VALUE_AT_ZERO.
      arg = gimple_call_arg (call, 0);
      prec = TYPE_PRECISION (TREE_TYPE (arg));
      mini = 0;
      maxi = prec - 1;
      mode = SCALAR_INT_TYPE_MODE (TREE_TYPE (arg));
      if (gimple_call_internal_p (call))
        {
          if (optab_handler (clz_optab, mode) != CODE_FOR_nothing
              && CLZ_DEFINED_VALUE_AT_ZERO (mode, zerov) == 2)
            {
              // Only handle the single common value.
              if (zerov == prec)
                maxi = prec;
              else
                // Magic value to give up, unless we can prove arg is non-zero.
                mini = -2;
            }
        }

      query.range_of_expr (r, arg, call);
      // From clz of minimum we can compute result maximum.
      if (r.constant_p ())
        {
          int newmaxi = prec - 1 - wi::floor_log2 (r.lower_bound ());
          // Argument is unsigned, so do nothing if it is [0, ...] range.
          if (newmaxi != prec)
            {
              mini = 0;
              maxi = newmaxi;
            }
        }
      else if (!range_includes_zero_p (&r))
        {
          maxi = prec - 1;
          mini = 0;
        }
      if (mini == -2)
        break;
      // From clz of maximum we can compute result minimum.
      if (r.constant_p ())
        {
          int newmini = prec - 1 - wi::floor_log2 (r.upper_bound ());
          if (newmini == prec)
            {
              // Argument range is [0, 0].  If CLZ_DEFINED_VALUE_AT_ZERO
              // is 2 with VALUE of prec, return [prec, prec], otherwise
              // ignore the range.
              if (maxi == prec)
                mini = prec;
            }
          else
            mini = newmini;
        }
      if (mini == -2)
        break;
      r.set (build_int_cst (type, mini), build_int_cst (type, maxi));
      return true;

    CASE_CFN_CTZ:
      // __builtin_ctz* return [0, prec-1], except for when the
      // argument is 0, but that is undefined behavior.
      //
      // For __builtin_ctz* consider argument of 0 always undefined
      // behavior, for internal fns depending on CTZ_DEFINED_VALUE_AT_ZERO.
      arg = gimple_call_arg (call, 0);
      prec = TYPE_PRECISION (TREE_TYPE (arg));
      mini = 0;
      maxi = prec - 1;
      mode = SCALAR_INT_TYPE_MODE (TREE_TYPE (arg));
      if (gimple_call_internal_p (call))
        {
          if (optab_handler (ctz_optab, mode) != CODE_FOR_nothing
              && CTZ_DEFINED_VALUE_AT_ZERO (mode, zerov) == 2)
            {
              // Handle only the two common values.
              if (zerov == -1)
                mini = -1;
              else if (zerov == prec)
                maxi = prec;
              else
                // Magic value to give up, unless we can prove arg is non-zero.
                mini = -2;
            }
        }
      query.range_of_expr (r, arg, call);
      if (!r.undefined_p ())
        {
          if (r.lower_bound () != 0)
            {
              mini = 0;
              maxi = prec - 1;
            }
          // If some high bits are known to be zero, we can decrease
          // the maximum.
          wide_int max = r.upper_bound ();
          if (max == 0)
            {
              // Argument is [0, 0].  If CTZ_DEFINED_VALUE_AT_ZERO
              // is 2 with value -1 or prec, return [-1, -1] or [prec, prec].
              // Otherwise ignore the range.
              if (mini == -1)
                maxi = -1;
              else if (maxi == prec)
                mini = prec;
            }
          // If value at zero is prec and 0 is in the range, we can't lower
          // the upper bound.  We could create two separate ranges though,
          // [0,floor_log2(max)][prec,prec] though.
          else if (maxi != prec)
            maxi = wi::floor_log2 (max);
        }
      if (mini == -2)
        break;
      r.set (build_int_cst (type, mini), build_int_cst (type, maxi));
      return true;

    CASE_CFN_CLRSB:
      arg = gimple_call_arg (call, 0);
      prec = TYPE_PRECISION (TREE_TYPE (arg));
      r.set (build_int_cst (type, 0), build_int_cst (type, prec - 1));
      return true;
    case CFN_UBSAN_CHECK_ADD:
      range_of_builtin_ubsan_call (query, r, call, PLUS_EXPR);
      return true;
    case CFN_UBSAN_CHECK_SUB:
      range_of_builtin_ubsan_call (query, r, call, MINUS_EXPR);
      return true;
    case CFN_UBSAN_CHECK_MUL:
      range_of_builtin_ubsan_call (query, r, call, MULT_EXPR);
      return true;

    case CFN_GOACC_DIM_SIZE:
    case CFN_GOACC_DIM_POS:
      // Optimizing these two internal functions helps the loop
      // optimizer eliminate outer comparisons.  Size is [1,N]
      // and pos is [0,N-1].
      {
        bool is_pos = func == CFN_GOACC_DIM_POS;
        int axis = oacc_get_ifn_dim_arg (call);
        int size = oacc_get_fn_dim_size (current_function_decl, axis);
        if (!size)
          // If it's dynamic, the backend might know a hardware limitation.
          size = targetm.goacc.dim_limit (axis);

        r.set (build_int_cst (type, is_pos ? 0 : 1),
               size
               ? build_int_cst (type, size - is_pos) : vrp_val_max (type));
        return true;
      }

    case CFN_BUILT_IN_STRLEN:
      if (tree lhs = gimple_call_lhs (call))
        if (ptrdiff_type_node
            && (TYPE_PRECISION (ptrdiff_type_node)
                == TYPE_PRECISION (TREE_TYPE (lhs))))
          {
            tree type = TREE_TYPE (lhs);
            tree max = vrp_val_max (ptrdiff_type_node);
            wide_int wmax
              = wi::to_wide (max, TYPE_PRECISION (TREE_TYPE (max)));
            tree range_min = build_zero_cst (type);
            // To account for the terminating NULL, the maximum length
            // is one less than the maximum array size, which in turn
            // is one less than PTRDIFF_MAX (or SIZE_MAX where it's
            // smaller than the former type).
            // FIXME: Use max_object_size() - 1 here.
            tree range_max = wide_int_to_tree (type, wmax - 2);
            r.set (range_min, range_max);
            return true;
          }
      break;
    default:
      break;
    }
  return false;
}


bool
gimple_ranger::range_of_builtin_call (irange &r, gcall *call)
{
  return ::range_of_builtin_call (*this, r, call);
}

// Calculate a range for COND_EXPR statement S and return it in R.
// If a range cannot be calculated, return false.

bool
gimple_ranger::range_of_cond_expr  (irange &r, gassign *s)
{
  int_range_max cond_range, range1, range2;
  tree cond = gimple_assign_rhs1 (s);
  tree op1 = gimple_assign_rhs2 (s);
  tree op2 = gimple_assign_rhs3 (s);

  gcc_checking_assert (gimple_assign_rhs_code (s) == COND_EXPR);
  gcc_checking_assert (useless_type_conversion_p  (TREE_TYPE (op1),
                                                   TREE_TYPE (op2)));
  if (!irange::supports_type_p (TREE_TYPE (op1)))
    return false;

  range_of_expr (cond_range, cond, s);
  range_of_expr (range1, op1, s);
  range_of_expr (range2, op2, s);

  // If the condition is known, choose the appropriate expression.
  if (cond_range.singleton_p ())
    {
      // False, pick second operand.
      if (cond_range.zero_p ())
        r = range2;
      else
        r = range1;
    }
  else
    {
      r = range1;
      r.union_ (range2);
    }
  return true;
}

bool
gimple_ranger::range_of_expr (irange &r, tree expr, gimple *stmt)
{
  if (!gimple_range_ssa_p (expr))
    return get_tree_range (r, expr);

  // If there is no statement, just get the global value.
  if (!stmt)
    {
      if (!m_cache.get_global_range (r, expr))
        r = gimple_range_global (expr);
      return true;
    }

  basic_block bb = gimple_bb (stmt);
  gimple *def_stmt = SSA_NAME_DEF_STMT (expr);

  // If name is defined in this block, try to get an range from S.
  if (def_stmt && gimple_bb (def_stmt) == bb)
    range_of_stmt (r, def_stmt, expr);
  else
    // Otherwise OP comes from outside this block, use range on entry.
    range_on_entry (r, bb, expr);

  // No range yet, see if there is a dereference in the block.
  // We don't care if it's between the def and a use within a block
  // because the entire block must be executed anyway.
  // FIXME:?? For non-call exceptions we could have a statement throw
  // which causes an early block exit.
  // in which case we may need to walk from S back to the def/top of block
  // to make sure the deref happens between S and there before claiming
  // there is a deref.   Punt for now.
  if (!cfun->can_throw_non_call_exceptions && r.varying_p () &&
      m_cache.m_non_null.non_null_deref_p (expr, bb))
    r = range_nonzero (TREE_TYPE (expr));

  return true;
}

// Return the range of NAME on entry to block BB in R.

void
gimple_ranger::range_on_entry (irange &r, basic_block bb, tree name)
{
  int_range_max entry_range;
  gcc_checking_assert (gimple_range_ssa_p (name));

  // Start with any known range
  range_of_stmt (r, SSA_NAME_DEF_STMT (name), name);

  // Now see if there is any on_entry value which may refine it.
  if (m_cache.block_range (entry_range, bb, name))
    r.intersect (entry_range);
}

// Calculate the range for NAME at the end of block BB and return it in R.
// Return false if no range can be calculated.

void
gimple_ranger::range_on_exit (irange &r, basic_block bb, tree name)
{
  // on-exit from the exit block?
  gcc_checking_assert (bb != EXIT_BLOCK_PTR_FOR_FN (cfun));
  gcc_checking_assert (gimple_range_ssa_p (name));

  gimple *s = last_stmt (bb);
  // If there is no statement in the block and this isn't the entry
  // block, go get the range_on_entry for this block.  For the entry
  // block, a NULL stmt will return the global value for NAME.
  if (!s && bb != ENTRY_BLOCK_PTR_FOR_FN (cfun))
    range_on_entry (r, bb, name);
  else
    range_of_expr (r, name, s);
  gcc_checking_assert (r.undefined_p ()
                       || range_compatible_p (r.type (), TREE_TYPE (name)));
}

// Calculate a range for NAME on edge E and return it in R.

bool
gimple_ranger::range_on_edge (irange &r, edge e, tree name)
{
  int_range_max edge_range;
  gcc_checking_assert (irange::supports_type_p (TREE_TYPE (name)));

  // PHI arguments can be constants, catch these here.
  if (!gimple_range_ssa_p (name))
    return range_of_expr (r, name);

  range_on_exit (r, e->src, name);
  gcc_checking_assert  (r.undefined_p ()
                        || range_compatible_p (r.type(), TREE_TYPE (name)));

  // Check to see if NAME is defined on edge e.
  if (m_cache.outgoing_edge_range_p (edge_range, e, name))
    r.intersect (edge_range);

  return true;
}

// Calculate a range for statement S and return it in R.  If NAME is
// provided it represents the SSA_NAME on the LHS of the statement.
// It is only required if there is more than one lhs/output.  Check
// the global cache for NAME first to see if the evaluation can be
// avoided.  If a range cannot be calculated, return false and UNDEFINED.

bool
gimple_ranger::range_of_stmt (irange &r, gimple *s, tree name)
{
  r.set_undefined ();

  if (!name)
    name = gimple_get_lhs (s);

  // If no name, simply call the base routine.
  if (!name)
    return calc_stmt (r, s, NULL_TREE);

  if (!gimple_range_ssa_p (name))
    return false;

  // Check if the stmt has already been processed, and is not stale.
  if (m_cache.get_non_stale_global_range (r, name))
    return true;

  // Otherwise calculate a new value and save it.
  calc_stmt (r, s, name);
  m_cache.set_global_range (name, r);
  return true;
}

// This routine will export whatever global ranges are known to GCC
// SSA_RANGE_NAME_INFO fields.

void
gimple_ranger::export_global_ranges ()
{
  unsigned x;
  int_range_max r;
  if (dump_file)
    {
      fprintf (dump_file, "Exported global range table\n");
      fprintf (dump_file, "===========================\n");
    }

  for ( x = 1; x < num_ssa_names; x++)
    {
      tree name = ssa_name (x);
      if (name && !SSA_NAME_IN_FREE_LIST (name)
          && gimple_range_ssa_p (name)
          && m_cache.get_global_range (r, name)
          && !r.varying_p())
        {
          // Make sure the new range is a subset of the old range.
          int_range_max old_range;
          old_range = gimple_range_global (name);
          old_range.intersect (r);
          /* Disable this while we fix tree-ssa/pr61743-2.c.  */
          //gcc_checking_assert (old_range == r);

          // WTF? Can't write non-null pointer ranges?? stupid set_range_info!
          if (!POINTER_TYPE_P (TREE_TYPE (name)) && !r.undefined_p ())
            {
              value_range vr = r;
              set_range_info (name, vr);
              if (dump_file)
                {
                  print_generic_expr (dump_file, name , TDF_SLIM);
                  fprintf (dump_file, " --> ");
                  vr.dump (dump_file);
                  fprintf (dump_file, "\n");
                  fprintf (dump_file, "         irange : ");
                  r.dump (dump_file);
                  fprintf (dump_file, "\n");
                }
            }
        }
    }
}

// Print the known table values to file F.

void
gimple_ranger::dump (FILE *f)
{
  basic_block bb;

  FOR_EACH_BB_FN (bb, cfun)
    {
      unsigned x;
      edge_iterator ei;
      edge e;
      int_range_max range;
      fprintf (f, "\n=========== BB %d ============\n", bb->index);
      m_cache.dump (f, bb);

      dump_bb (f, bb, 4, TDF_NONE);

      // Now find any globals defined in this block.
      for (x = 1; x < num_ssa_names; x++)
        {
          tree name = ssa_name (x);
          if (gimple_range_ssa_p (name) && SSA_NAME_DEF_STMT (name) &&
              gimple_bb (SSA_NAME_DEF_STMT (name)) == bb &&
              m_cache.get_global_range (range, name))
            {
              if (!range.varying_p ())
               {
                 print_generic_expr (f, name, TDF_SLIM);
                 fprintf (f, " : ");
                 range.dump (f);
                 fprintf (f, "\n");
               }

            }
        }

      // And now outgoing edges, if they define anything.
      FOR_EACH_EDGE (e, ei, bb->succs)
        {
          for (x = 1; x < num_ssa_names; x++)
            {
              tree name = gimple_range_ssa_p (ssa_name (x));
              if (name && m_cache.outgoing_edge_range_p (range, e, name))
                {
                  gimple *s = SSA_NAME_DEF_STMT (name);
                  // Only print the range if this is the def block, or
                  // the on entry cache for either end of the edge is
                  // set.
                  if ((s && bb == gimple_bb (s)) ||
                      m_cache.block_range (range, bb, name, false) ||
                      m_cache.block_range (range, e->dest, name, false))
                    {
                      range_on_edge (range, e, name);
                      if (!range.varying_p ())
                        {
                          fprintf (f, "%d->%d ", e->src->index,
                                   e->dest->index);
                          char c = ' ';
                          if (e->flags & EDGE_TRUE_VALUE)
                            fprintf (f, " (T)%c", c);
                          else if (e->flags & EDGE_FALSE_VALUE)
                            fprintf (f, " (F)%c", c);
                          else
                            fprintf (f, "     ");
                          print_generic_expr (f, name, TDF_SLIM);
                          fprintf(f, " : \t");
                          range.dump(f);
                          fprintf (f, "\n");
                        }
                    }
                }
            }
        }
    }

  m_cache.dump (dump_file, (dump_flags & TDF_DETAILS) != 0);
}

// If SCEV has any information about phi node NAME, return it as a range in R.

void
gimple_ranger::range_of_ssa_name_with_loop_info (irange &r, tree name,
                                                 class loop *l, gphi *phi)
{
  gcc_checking_assert (TREE_CODE (name) == SSA_NAME);
  tree min, max, type = TREE_TYPE (name);
  if (bounds_of_var_in_loop (&min, &max, this, l, phi, name))
    {
      // ?? We could do better here.  Since MIN/MAX can only be an
      // SSA, SSA +- INTEGER_CST, or INTEGER_CST, we could easily call
      // the ranger and solve anything not an integer.
      if (TREE_CODE (min) != INTEGER_CST)
        min = vrp_val_min (type);
      if (TREE_CODE (max) != INTEGER_CST)
        max = vrp_val_max (type);
      r.set (min, max);
    }
  else
    r.set_varying (type);
}

// --------------------------------------------------------------------------
// trace_ranger implementation.


trace_ranger::trace_ranger ()
{
  indent = 0;
  trace_count = 0;
}

// If dumping, return true and print the prefix for the next output line.

bool
trace_ranger::dumping (unsigned counter, bool trailing)
{
  if (dump_file && (dump_flags & TDF_DETAILS))
    {
      // Print counter index as well as INDENT spaces.
      if (!trailing)
        fprintf (dump_file, " %-7u ", counter);
      else
        fprintf (dump_file, "         ");
      unsigned x;
      for (x = 0; x< indent; x++)
        fputc (' ', dump_file);
      return true;
    }
  return false;
}

// After calling a routine, if dumping, print the CALLER, NAME, and RESULT,
// returning RESULT.

bool
trace_ranger::trailer (unsigned counter, const char *caller, bool result,
                       tree name, const irange &r)
{
  if (dumping (counter, true))
    {
      indent -= bump;
      fputs(result ? "TRUE : " : "FALSE : ", dump_file);
      fprintf (dump_file, "(%u) ", counter);
      fputs (caller, dump_file);
      fputs (" (",dump_file);
      if (name)
        print_generic_expr (dump_file, name, TDF_SLIM);
      fputs (") ",dump_file);
      if (result)
        {
          r.dump (dump_file);
          fputc('\n', dump_file);
        }
      else
        fputc('\n', dump_file);
      // Marks the end of a request.
      if (indent == 0)
        fputc('\n', dump_file);
    }
  return result;
}

// Tracing version of range_on_edge.  Call it with printing wrappers.

bool
trace_ranger::range_on_edge (irange &r, edge e, tree name)
{
  unsigned idx = ++trace_count;
  if (dumping (idx))
    {
      fprintf (dump_file, "range_on_edge (");
      print_generic_expr (dump_file, name, TDF_SLIM);
      fprintf (dump_file, ") on edge %d->%d\n", e->src->index, e->dest->index);
      indent += bump;
    }

  bool res = gimple_ranger::range_on_edge (r, e, name);
  trailer (idx, "range_on_edge", true, name, r);
  return res;
}

// Tracing version of range_on_entry.  Call it with printing wrappers.

void
trace_ranger::range_on_entry (irange &r, basic_block bb, tree name)
{
  unsigned idx = ++trace_count;
  if (dumping (idx))
    {
      fprintf (dump_file, "range_on_entry (");
      print_generic_expr (dump_file, name, TDF_SLIM);
      fprintf (dump_file, ") to BB %d\n", bb->index);
      indent += bump;
    }

  gimple_ranger::range_on_entry (r, bb, name);

  trailer (idx, "range_on_entry", true, name, r);
}

// Tracing version of range_on_exit.  Call it with printing wrappers.

void
trace_ranger::range_on_exit (irange &r, basic_block bb, tree name)
{
  unsigned idx = ++trace_count;
  if (dumping (idx))
    {
      fprintf (dump_file, "range_on_exit (");
      print_generic_expr (dump_file, name, TDF_SLIM);
      fprintf (dump_file, ") from BB %d\n", bb->index);
      indent += bump;
    }

  gimple_ranger::range_on_exit (r, bb, name);

  trailer (idx, "range_on_exit", true, name, r);
}

// Tracing version of range_of_stmt.  Call it with printing wrappers.

bool
trace_ranger::range_of_stmt (irange &r, gimple *s, tree name)
{
  bool res;
  unsigned idx = ++trace_count;
  if (dumping (idx))
    {
      fprintf (dump_file, "range_of_stmt (");
      if (name)
        print_generic_expr (dump_file, name, TDF_SLIM);
      fputs (") at stmt ", dump_file);
      print_gimple_stmt (dump_file, s, 0, TDF_SLIM);
      indent += bump;
    }

  res = gimple_ranger::range_of_stmt (r, s, name);

  return trailer (idx, "range_of_stmt", res, name, r);
}

// Tracing version of range_of_expr.  Call it with printing wrappers.

bool
trace_ranger::range_of_expr (irange &r, tree name, gimple *s)
{
  bool res;
  unsigned idx = ++trace_count;
  if (dumping (idx))
    {
      fprintf (dump_file, "range_of_expr(");
      print_generic_expr (dump_file, name, TDF_SLIM);
      fputs (")", dump_file);
      if (s)
        {
          fputs (" at stmt ", dump_file);
          print_gimple_stmt (dump_file, s, 0, TDF_SLIM);
        }
      else
        fputs ("\n", dump_file);
      indent += bump;
    }

  res = gimple_ranger::range_of_expr (r, name, s);

  return trailer (idx, "range_of_expr", res, name, r);
}