gcc/gimple-range-edge.cc

   1 /* Gimple range edge functionality.
   2    Copyright (C) 2020-2023 Free Software Foundation, Inc.
   3    Contributed by Andrew MacLeod <amacleod@redhat.com>
   4    and Aldy Hernandez <aldyh@redhat.com>.
   5
   6 This file is part of GCC.
   7
   8 GCC is free software; you can redistribute it and/or modify
   9 it under the terms of the GNU General Public License as published by
  10 the Free Software Foundation; either version 3, or (at your option)
  11 any later version.
  12
  13 GCC is distributed in the hope that it will be useful,
  14 but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 GNU General Public License for more details.
  17
  18 You should have received a copy of the GNU General Public License
  19 along with GCC; see the file COPYING3.  If not see
  20 <http://www.gnu.org/licenses/>.  */
  21
  22
  23 #include "config.h"
  24 #include "system.h"
  25 #include "coretypes.h"
  26 #include "backend.h"
  27 #include "tree.h"
  28 #include "gimple.h"
  29 #include "ssa.h"
  30 #include "gimple-pretty-print.h"
  31 #include "gimple-iterator.h"
  32 #include "tree-cfg.h"
  33 #include "gimple-range.h"
  34 #include "value-range-storage.h"
  35
  36 // If there is a range control statement at the end of block BB, return it.
  37 // Otherwise return NULL.
  38
  39 gimple *
  40 gimple_outgoing_range_stmt_p (basic_block bb)
  41 {
  42   gimple_stmt_iterator gsi = gsi_last_nondebug_bb (bb);
  43   if (!gsi_end_p (gsi))
  44     {
  45       gimple *s = gsi_stmt (gsi);
  46       if (is_a<gcond *> (s) && gimple_range_op_handler::supported_p (s))
  47         return gsi_stmt (gsi);
  48       if (is_a <gswitch *> (s))
  49         return gsi_stmt (gsi);
  50     }
  51   return NULL;
  52 }
  53
  54
  55 // Return a TRUE or FALSE range representing the edge value of a GCOND.
  56
  57 void
  58 gcond_edge_range (irange &r, edge e)
  59 {
  60   gcc_checking_assert (e->flags & (EDGE_TRUE_VALUE | EDGE_FALSE_VALUE));
  61   if (e->flags & EDGE_TRUE_VALUE)
  62     r = int_range<2> (boolean_true_node, boolean_true_node);
  63   else
  64     r = int_range<2> (boolean_false_node, boolean_false_node);
  65 }
  66
  67
  68 gimple_outgoing_range::gimple_outgoing_range (int max_sw_edges)
  69 {
  70   m_edge_table = NULL;
  71   m_max_edges = max_sw_edges;
  72   m_range_allocator = new obstack_vrange_allocator;
  73 }
  74
  75
  76 gimple_outgoing_range::~gimple_outgoing_range ()
  77 {
  78   if (m_edge_table)
  79     delete m_edge_table;
  80   delete m_range_allocator;
  81 }
  82
  83
  84 // Get a range for a switch edge E from statement S and return it in R.
  85 // Use a cached value if it exists, or calculate it if not.
  86
  87 bool
  88 gimple_outgoing_range::switch_edge_range (irange &r, gswitch *sw, edge e)
  89 {
  90   // ADA currently has cases where the index is 64 bits and the case
  91   // arguments are 32 bit, causing a trap when we create a case_range.
  92   // Until this is resolved (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87798)
  93   // punt on switches where the labels don't match the argument.
  94   if (gimple_switch_num_labels (sw) > 1 &&
  95       TYPE_PRECISION (TREE_TYPE (CASE_LOW (gimple_switch_label (sw, 1)))) !=
  96       TYPE_PRECISION (TREE_TYPE (gimple_switch_index (sw))))
  97     return false;
  98
  99    if (!m_edge_table)
 100      m_edge_table = new hash_map<edge, irange *> (n_edges_for_fn (cfun));
 101
 102    irange **val = m_edge_table->get (e);
 103    if (!val)
 104      {
 105        calc_switch_ranges (sw);
 106        val = m_edge_table->get (e);
 107        gcc_checking_assert (val);
 108      }
 109     r = **val;
 110   return true;
 111 }
 112
 113
 114 // Calculate all switch edges from SW and cache them in the hash table.
 115
 116 void
 117 gimple_outgoing_range::calc_switch_ranges (gswitch *sw)
 118 {
 119   bool existed;
 120   unsigned x, lim;
 121   lim = gimple_switch_num_labels (sw);
 122   tree type = TREE_TYPE (gimple_switch_index (sw));
 123   edge default_edge = gimple_switch_default_edge (cfun, sw);
 124
 125   // This should be the first call into this switch.
 126   //
 127   // Allocate an int_range_max for the default range case, start with
 128   // varying and intersect each other case from it.
 129   int_range_max default_range (type);
 130
 131   for (x = 1; x < lim; x++)
 132     {
 133       edge e = gimple_switch_edge (cfun, sw, x);
 134
 135       // If this edge is the same as the default edge, do nothing else.
 136       if (e == default_edge)
 137         continue;
 138
 139       tree low = CASE_LOW (gimple_switch_label (sw, x));
 140       tree high = CASE_HIGH (gimple_switch_label (sw, x));
 141       if (!high)
 142         high = low;
 143
 144       // Remove the case range from the default case.
 145       int_range_max def_range (low, high);
 146       range_cast (def_range, type);
 147       def_range.invert ();
 148       default_range.intersect (def_range);
 149
 150       // Create/union this case with anything on else on the edge.
 151       int_range_max case_range (low, high);
 152       range_cast (case_range, type);
 153       irange *&slot = m_edge_table->get_or_insert (e, &existed);
 154       if (existed)
 155         {
 156           // If this doesn't change the value, move on.
 157           if (!case_range.union_ (*slot))
 158            continue;
 159           if (slot->fits_p (case_range))
 160             {
 161               *slot = case_range;
 162               continue;
 163             }
 164         }
 165       // If there was an existing range and it doesn't fit, we lose the memory.
 166       // It'll get reclaimed when the obstack is freed.  This seems less
 167       // intrusive than allocating max ranges for each case.
 168       slot = m_range_allocator->clone <irange> (case_range);
 169     }
 170
 171   irange *&slot = m_edge_table->get_or_insert (default_edge, &existed);
 172   // This should be the first call into this switch.
 173   gcc_checking_assert (!existed);
 174   irange *dr = m_range_allocator->clone <irange> (default_range);
 175   slot = dr;
 176 }
 177
 178
 179 // Calculate the range forced on on edge E by control flow, return it
 180 // in R.  Return the statement which defines the range, otherwise
 181 // return NULL
 182
 183 gimple *
 184 gimple_outgoing_range::edge_range_p (irange &r, edge e)
 185 {
 186   if (single_succ_p (e->src))
 187     return NULL;
 188
 189   // Determine if there is an outgoing edge.
 190   gimple *s = gimple_outgoing_range_stmt_p (e->src);
 191   if (!s)
 192     return NULL;
 193
 194   if (is_a<gcond *> (s))
 195     {
 196       gcond_edge_range (r, e);
 197       return s;
 198     }
 199
 200   // Only process switches if it within the size limit.
 201   if (EDGE_COUNT (e->src->succs) > (unsigned)m_max_edges)
 202     return NULL;
 203
 204   gcc_checking_assert (is_a<gswitch *> (s));
 205   gswitch *sw = as_a<gswitch *> (s);
 206
 207   // Switches can only be integers.
 208   if (switch_edge_range (as_a <irange> (r), sw, e))
 209     return s;
 210
 211   return NULL;
 212 }