gcc/gcse-common.cc

   1 /* Shared code for before and after reload gcse implementations.
   2    Copyright (C) 1997-2023 Free Software Foundation, Inc.
   3
   4    This file is part of GCC.
   5
   6    GCC is free software; you can redistribute it and/or modify it under
   7    the terms of the GNU General Public License as published by the Free
   8    Software Foundation; either version 3, or (at your option) any later
   9    version.
  10
  11    GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  12    WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14    for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with GCC; see the file COPYING3.  If not see
  18    <http://www.gnu.org/licenses/>.
  19
  20    It is expected that more hunks of gcse.cc and postreload-gcse.cc should
  21    migrate into this file.  */
  22
  23 #include "config.h"
  24 #include "system.h"
  25 #include "coretypes.h"
  26 #include "backend.h"
  27 #include "rtl.h"
  28 #include "df.h"
  29 #include "gcse-common.h"
  30
  31
  32 /* Record all of the canonicalized MEMs of record_last_mem_set_info's insn.
  33    Note we store a pair of elements in the list, so they have to be
  34    taken off pairwise.  */
  35
  36 void
  37 canon_list_insert (rtx dest, const_rtx x ATTRIBUTE_UNUSED, void *data)
  38 {
  39   rtx dest_addr;
  40   int bb;
  41   modify_pair pair;
  42
  43   while (GET_CODE (dest) == SUBREG
  44       || GET_CODE (dest) == ZERO_EXTRACT
  45       || GET_CODE (dest) == STRICT_LOW_PART)
  46     dest = XEXP (dest, 0);
  47
  48   /* If DEST is not a MEM, then it will not conflict with a load.  Note
  49      that function calls are assumed to clobber memory, but are handled
  50      elsewhere.  */
  51
  52   if (! MEM_P (dest))
  53     return;
  54
  55   dest_addr = get_addr (XEXP (dest, 0));
  56   dest_addr = canon_rtx (dest_addr);
  57   rtx_insn *insn = ((struct gcse_note_stores_info *)data)->insn;
  58   bb = BLOCK_FOR_INSN (insn)->index;
  59
  60   pair.dest = dest;
  61   pair.dest_addr = dest_addr;
  62   vec<modify_pair> *canon_mem_list
  63     = ((struct gcse_note_stores_info *)data)->canon_mem_list;
  64   canon_mem_list[bb].safe_push (pair);
  65 }
  66
  67 /* Record memory modification information for INSN.  We do not actually care
  68    about the memory location(s) that are set, or even how they are set (consider
  69    a CALL_INSN).  We merely need to record which insns modify memory.  */
  70
  71 void
  72 record_last_mem_set_info_common (rtx_insn *insn,
  73                                  vec<rtx_insn *> *modify_mem_list,
  74                                  vec<modify_pair> *canon_modify_mem_list,
  75                                  bitmap modify_mem_list_set,
  76                                  bitmap blocks_with_calls)
  77
  78 {
  79   int bb;
  80
  81   bb = BLOCK_FOR_INSN (insn)->index;
  82   modify_mem_list[bb].safe_push (insn);
  83   bitmap_set_bit (modify_mem_list_set, bb);
  84
  85   if (CALL_P (insn))
  86     bitmap_set_bit (blocks_with_calls, bb);
  87   else
  88     {
  89       struct gcse_note_stores_info data;
  90       data.insn = insn;
  91       data.canon_mem_list = canon_modify_mem_list;
  92       note_stores (insn, canon_list_insert, (void*) &data);
  93     }
  94 }
  95
  96
  97 /* For each block, compute whether X is transparent.  X is either an
  98    expression or an assignment [though we don't care which, for this context
  99    an assignment is treated as an expression].  For each block where an
 100    element of X is modified, reset the INDX bit in BMAP.
 101
 102    BLOCKS_WITH_CALLS indicates which blocks contain CALL_INSNs which kill
 103    memory.
 104
 105    MODIFY_MEM_LIST_SET indicates which blocks have memory stores which might
 106    kill a particular memory location.
 107
 108    CANON_MODIFY_MEM_LIST is the canonicalized list of memory locations modified
 109    for each block.  */
 110
 111 void
 112 compute_transp (const_rtx x, int indx, sbitmap *bmap,
 113                 bitmap blocks_with_calls,
 114                 bitmap modify_mem_list_set,
 115                 vec<modify_pair> *canon_modify_mem_list)
 116 {
 117   int i, j;
 118   enum rtx_code code;
 119   const char *fmt;
 120
 121   /* repeat is used to turn tail-recursion into iteration since GCC
 122      can't do it when there's no return value.  */
 123  repeat:
 124
 125   if (x == 0)
 126     return;
 127
 128   code = GET_CODE (x);
 129   switch (code)
 130     {
 131     case REG:
 132         {
 133           df_ref def;
 134           for (def = DF_REG_DEF_CHAIN (REGNO (x));
 135                def;
 136                def = DF_REF_NEXT_REG (def))
 137             bitmap_clear_bit (bmap[DF_REF_BB (def)->index], indx);
 138         }
 139
 140       return;
 141
 142     case MEM:
 143       if (! MEM_READONLY_P (x))
 144         {
 145           bitmap_iterator bi;
 146           unsigned bb_index;
 147           rtx x_addr;
 148
 149           x_addr = get_addr (XEXP (x, 0));
 150           x_addr = canon_rtx (x_addr);
 151
 152           /* First handle all the blocks with calls.  We don't need to
 153              do any list walking for them.  */
 154           EXECUTE_IF_SET_IN_BITMAP (blocks_with_calls, 0, bb_index, bi)
 155             {
 156               bitmap_clear_bit (bmap[bb_index], indx);
 157             }
 158
 159           /* Now iterate over the blocks which have memory modifications
 160              but which do not have any calls.  */
 161           EXECUTE_IF_AND_COMPL_IN_BITMAP (modify_mem_list_set,
 162                                           blocks_with_calls,
 163                                           0, bb_index, bi)
 164             {
 165               vec<modify_pair> list
 166                 = canon_modify_mem_list[bb_index];
 167               modify_pair *pair;
 168               unsigned ix;
 169
 170               FOR_EACH_VEC_ELT_REVERSE (list, ix, pair)
 171                 {
 172                   rtx dest = pair->dest;
 173                   rtx dest_addr = pair->dest_addr;
 174
 175                   if (canon_true_dependence (dest, GET_MODE (dest),
 176                                              dest_addr, x, x_addr))
 177                     {
 178                       bitmap_clear_bit (bmap[bb_index], indx);
 179                       break;
 180                     }
 181                 }
 182             }
 183         }
 184
 185       x = XEXP (x, 0);
 186       goto repeat;
 187
 188     case PC:
 189     case CONST:
 190     CASE_CONST_ANY:
 191     case SYMBOL_REF:
 192     case LABEL_REF:
 193     case ADDR_VEC:
 194     case ADDR_DIFF_VEC:
 195       return;
 196
 197     default:
 198       break;
 199     }
 200
 201   for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--)
 202     {
 203       if (fmt[i] == 'e')
 204         {
 205           /* If we are about to do the last recursive call
 206              needed at this level, change it into iteration.
 207              This function is called enough to be worth it.  */
 208           if (i == 0)
 209             {
 210               x = XEXP (x, i);
 211               goto repeat;
 212             }
 213
 214           compute_transp (XEXP (x, i), indx, bmap, blocks_with_calls,
 215                           modify_mem_list_set, canon_modify_mem_list);
 216         }
 217       else if (fmt[i] == 'E')
 218         for (j = 0; j < XVECLEN (x, i); j++)
 219           compute_transp (XVECEXP (x, i, j), indx, bmap, blocks_with_calls,
 220                           modify_mem_list_set, canon_modify_mem_list);
 221     }
 222 }