git.sur5r.net Git - cc65/blob - src/cc65/coptsub.c

   1 /*****************************************************************************/
   2 /*                                                                           */
   3 /*                                 coptsub.c                                 */
   4 /*                                                                           */
   5 /*                      Optimize subtraction sequences                       */
   6 /*                                                                           */
   7 /*                                                                           */
   8 /*                                                                           */
   9 /* (C) 2001-2006, Ullrich von Bassewitz                                      */
  10 /*                Römerstrasse 52                                            */
  11 /*                D-70794 Filderstadt                                        */
  12 /* EMail:         uz@cc65.org                                                */
  13 /*                                                                           */
  14 /*                                                                           */
  15 /* This software is provided 'as-is', without any expressed or implied       */
  16 /* warranty.  In no event will the authors be held liable for any damages    */
  17 /* arising from the use of this software.                                    */
  18 /*                                                                           */
  19 /* Permission is granted to anyone to use this software for any purpose,     */
  20 /* including commercial applications, and to alter it and redistribute it    */
  21 /* freely, subject to the following restrictions:                            */
  22 /*                                                                           */
  23 /* 1. The origin of this software must not be misrepresented; you must not   */
  24 /*    claim that you wrote the original software. If you use this software   */
  25 /*    in a product, an acknowledgment in the product documentation would be  */
  26 /*    appreciated but is not required.                                       */
  27 /* 2. Altered source versions must be plainly marked as such, and must not   */
  28 /*    be misrepresented as being the original software.                      */
  29 /* 3. This notice may not be removed or altered from any source              */
  30 /*    distribution.                                                          */
  31 /*                                                                           */
  32 /*****************************************************************************/
  33
  34
  35
  36 /* common */
  37 #include "chartype.h"
  38
  39 /* cc65 */
  40 #include "codeent.h"
  41 #include "codeinfo.h"
  42 #include "coptsub.h"
  43
  44
  45
  46 /*****************************************************************************/
  47 /*                           Optimize subtractions                           */
  48 /*****************************************************************************/
  49
  50
  51
  52 unsigned OptSub1 (CodeSeg* S)
  53 /* Search for the sequence
  54 **
  55 **      sbc     ...
  56 **      bcs     L
  57 **      dex
  58 ** L:
  59 **
  60 ** and remove the handling of the high byte if X is not used later.
  61 */
  62 {
  63     unsigned Changes = 0;
  64
  65     /* Walk over the entries */
  66     unsigned I = 0;
  67     while (I < CS_GetEntryCount (S)) {
  68
  69         CodeEntry* L[3];
  70
  71         /* Get next entry */
  72         CodeEntry* E = CS_GetEntry (S, I);
  73
  74         /* Check for the sequence */
  75         if (E->OPC == OP65_SBC                               &&
  76             CS_GetEntries (S, L, I+1, 3)                     &&
  77             (L[0]->OPC == OP65_BCS || L[0]->OPC == OP65_JCS) &&
  78             L[0]->JumpTo != 0                                &&
  79             !CE_HasLabel (L[0])                              &&
  80             L[1]->OPC == OP65_DEX                            &&
  81             !CE_HasLabel (L[1])                              &&
  82             L[0]->JumpTo->Owner == L[2]                      &&
  83             !RegXUsed (S, I+3)) {
  84
  85             /* Remove the bcs/dex */
  86             CS_DelEntries (S, I+1, 2);
  87
  88             /* Remember, we had changes */
  89             ++Changes;
  90
  91         }
  92
  93         /* Next entry */
  94         ++I;
  95
  96     }
  97
  98     /* Return the number of changes made */
  99     return Changes;
 100 }
 101
 102
 103
 104 unsigned OptSub2 (CodeSeg* S)
 105 /* Search for the sequence
 106 **
 107 **      lda     xx
 108 **      sec
 109 **      sta     tmp1
 110 **      lda     yy
 111 **      sbc     tmp1
 112 **      sta     yy
 113 **
 114 ** and replace it by
 115 **
 116 **      sec
 117 **      lda     yy
 118 **      sbc     xx
 119 **      sta     yy
 120 */
 121 {
 122     unsigned Changes = 0;
 123
 124     /* Walk over the entries */
 125     unsigned I = 0;
 126     while (I < CS_GetEntryCount (S)) {
 127
 128         CodeEntry* L[5];
 129
 130         /* Get next entry */
 131         CodeEntry* E = CS_GetEntry (S, I);
 132
 133         /* Check for the sequence */
 134         if (E->OPC == OP65_LDA                             &&
 135             !CS_RangeHasLabel (S, I+1, 5)                  &&
 136             CS_GetEntries (S, L, I+1, 5)                   &&
 137             L[0]->OPC == OP65_SEC                          &&
 138             L[1]->OPC == OP65_STA                          &&
 139             strcmp (L[1]->Arg, "tmp1") == 0                &&
 140             L[2]->OPC == OP65_LDA                          &&
 141             L[3]->OPC == OP65_SBC                          &&
 142             strcmp (L[3]->Arg, "tmp1") == 0                &&
 143             L[4]->OPC == OP65_STA                          &&
 144             strcmp (L[4]->Arg, L[2]->Arg) == 0) {
 145
 146             /* Remove the store to tmp1 */
 147             CS_DelEntry (S, I+2);
 148
 149             /* Remove the subtraction */
 150             CS_DelEntry (S, I+3);
 151
 152             /* Move the lda to the position of the subtraction and change the
 153             ** op to SBC.
 154             */
 155             CS_MoveEntry (S, I, I+3);
 156             CE_ReplaceOPC (E, OP65_SBC);
 157
 158             /* If the sequence head had a label, move this label back to the
 159             ** head.
 160             */
 161             if (CE_HasLabel (E)) {
 162                 CS_MoveLabels (S, E, L[0]);
 163             }
 164
 165             /* Remember, we had changes */
 166             ++Changes;
 167
 168         }
 169
 170         /* Next entry */
 171         ++I;
 172
 173     }
 174
 175     /* Return the number of changes made */
 176     return Changes;
 177 }
 178
 179
 180
 181 unsigned OptSub3 (CodeSeg* S)
 182 /* Search for a call to decaxn and replace it by an 8 bit sub if the X register
 183 ** is not used later.
 184 */
 185 {
 186     unsigned Changes = 0;
 187
 188     /* Walk over the entries */
 189     unsigned I = 0;
 190     while (I < CS_GetEntryCount (S)) {
 191
 192         CodeEntry* E;
 193
 194         /* Get next entry */
 195         E = CS_GetEntry (S, I);
 196
 197         /* Check for the sequence */
 198         if (E->OPC == OP65_JSR                          &&
 199             strncmp (E->Arg, "decax", 5) == 0           &&
 200             IsDigit (E->Arg[5])                         &&
 201             E->Arg[6] == '\0'                           &&
 202             !RegXUsed (S, I+1)) {
 203
 204             CodeEntry* X;
 205             const char* Arg;
 206
 207             /* Insert new code behind the sequence */
 208             X = NewCodeEntry (OP65_SEC, AM65_IMP, 0, 0, E->LI);
 209             CS_InsertEntry (S, X, I+1);
 210
 211             Arg = MakeHexArg (E->Arg[5] - '0');
 212             X = NewCodeEntry (OP65_SBC, AM65_IMM, Arg, 0, E->LI);
 213             CS_InsertEntry (S, X, I+2);
 214
 215             /* Delete the old code */
 216             CS_DelEntry (S, I);
 217
 218             /* Remember, we had changes */
 219             ++Changes;
 220
 221         }
 222
 223         /* Next entry */
 224         ++I;
 225
 226     }
 227
 228     /* Return the number of changes made */
 229     return Changes;
 230 }