gcc/gimple-range-edge.cc

   1 /* Gimple range edge functionaluity.
   2    Copyright (C) 2020-2022 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
  35 // If there is a range control statment at the end of block BB, return it.
  36 // Otherwise return NULL.
  37
  38 gimple *
  39 gimple_outgoing_range_stmt_p (basic_block bb)
  40 {
  41   gimple_stmt_iterator gsi = gsi_last_nondebug_bb (bb);
  42   if (!gsi_end_p (gsi))
  43     {
  44       gimple *s = gsi_stmt (gsi);
  45       if (is_a<gcond *> (s) && range_op_handler (s))
  46         return gsi_stmt (gsi);
  47       if (is_a <gswitch *> (s))
  48         return gsi_stmt (gsi);
  49     }
  50   return NULL;
  51 }
  52
  53
  54 // Return a TRUE or FALSE range representing the edge value of a GCOND.
  55
  56 void
  57 gcond_edge_range (irange &r, edge e)
  58 {
  59   gcc_checking_assert (e->flags & (EDGE_TRUE_VALUE | EDGE_FALSE_VALUE));
  60   if (e->flags & EDGE_TRUE_VALUE)
  61     r = int_range<2> (boolean_true_node, boolean_true_node);
  62   else
  63     r = int_range<2> (boolean_false_node, boolean_false_node);
  64 }
  65
  66
  67 gimple_outgoing_range::gimple_outgoing_range (int max_sw_edges)
  68 {
  69   m_edge_table = NULL;
  70   m_max_edges = max_sw_edges;
  71 }
  72
  73
  74 gimple_outgoing_range::~gimple_outgoing_range ()
  75 {
  76   if (m_edge_table)
  77     delete m_edge_table;
  78 }
  79
  80
  81 // Get a range for a switch edge E from statement S and return it in R.
  82 // Use a cached value if it exists, or calculate it if not.
  83
  84 bool
  85 gimple_outgoing_range::switch_edge_range (irange &r, gswitch *sw, edge e)
  86 {
  87   // ADA currently has cases where the index is 64 bits and the case
  88   // arguments are 32 bit, causing a trap when we create a case_range.
  89   // Until this is resolved (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87798)
  90   // punt on switches where the labels dont match the argument.
  91   if (gimple_switch_num_labels (sw) > 1 &&
  92       TYPE_PRECISION (TREE_TYPE (CASE_LOW (gimple_switch_label (sw, 1)))) !=
  93       TYPE_PRECISION (TREE_TYPE (gimple_switch_index (sw))))
  94     return false;
  95
  96    if (!m_edge_table)
  97      m_edge_table = new hash_map<edge, irange *> (n_edges_for_fn (cfun));
  98
  99    irange **val = m_edge_table->get (e);
 100    if (!val)
 101      {
 102        calc_switch_ranges (sw);
 103        val = m_edge_table->get (e);
 104        gcc_checking_assert (val);
 105      }
 106     r = **val;
 107   return true;
 108 }
 109
 110
 111 // Calculate all switch edges from SW and cache them in the hash table.
 112
 113 void
 114 gimple_outgoing_range::calc_switch_ranges (gswitch *sw)
 115 {
 116   bool existed;
 117   unsigned x, lim;
 118   lim = gimple_switch_num_labels (sw);
 119   tree type = TREE_TYPE (gimple_switch_index (sw));
 120   edge default_edge = gimple_switch_default_edge (cfun, sw);
 121
 122   // This should be the first call into this switch.
 123   //
 124   // Allocate an int_range_max for the default range case, start with
 125   // varying and intersect each other case from it.
 126   int_range_max default_range (type);
 127
 128   for (x = 1; x < lim; x++)
 129     {
 130       edge e = gimple_switch_edge (cfun, sw, x);
 131
 132       // If this edge is the same as the default edge, do nothing else.
 133       if (e == default_edge)
 134         continue;
 135
 136       tree low = CASE_LOW (gimple_switch_label (sw, x));
 137       tree high = CASE_HIGH (gimple_switch_label (sw, x));
 138       if (!high)
 139         high = low;
 140
 141       // Remove the case range from the default case.
 142       int_range_max def_range (low, high);
 143       range_cast (def_range, type);
 144       def_range.invert ();
 145       default_range.intersect (def_range);
 146
 147       // Create/union this case with anything on else on the edge.
 148       int_range_max case_range (low, high);
 149       range_cast (case_range, type);
 150       irange *&slot = m_edge_table->get_or_insert (e, &existed);
 151       if (existed)
 152         {
 153           // If this doesn't change the value, move on.
 154           if (!case_range.union_ (*slot))
 155            continue;
 156           if (slot->fits_p (case_range))
 157             {
 158               *slot = case_range;
 159               continue;
 160             }
 161         }
 162       // If there was an existing range and it doesn't fit, we lose the memory.
 163       // It'll get reclaimed when the obstack is freed.  This seems less
 164       // intrusive than allocating max ranges for each case.
 165       slot = m_range_allocator.clone <irange> (case_range);
 166     }
 167
 168   irange *&slot = m_edge_table->get_or_insert (default_edge, &existed);
 169   // This should be the first call into this switch.
 170   gcc_checking_assert (!existed);
 171   irange *dr = m_range_allocator.clone <irange> (default_range);
 172   slot = dr;
 173 }
 174
 175
 176 // Calculate the range forced on on edge E by control flow, return it
 177 // in R.  Return the statment which defines the range, otherwise
 178 // return NULL
 179
 180 gimple *
 181 gimple_outgoing_range::edge_range_p (irange &r, edge e)
 182 {
 183   if (single_succ_p (e->src))
 184     return NULL;
 185
 186   // Determine if there is an outgoing edge.
 187   gimple *s = gimple_outgoing_range_stmt_p (e->src);
 188   if (!s)
 189     return NULL;
 190
 191   if (is_a<gcond *> (s))
 192     {
 193       gcond_edge_range (r, e);
 194       return s;
 195     }
 196
 197   // Only process switches if it within the size limit.
 198   if (EDGE_COUNT (e->src->succs) > (unsigned)m_max_edges)
 199     return NULL;
 200
 201   gcc_checking_assert (is_a<gswitch *> (s));
 202   gswitch *sw = as_a<gswitch *> (s);
 203
 204   // Switches can only be integers.
 205   if (switch_edge_range (as_a <irange> (r), sw, e))
 206     return s;
 207
 208   return NULL;
 209 }