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

   1 /*****************************************************************************/
   2 /*                                                                           */
   3 /*                                copttest.c                                 */
   4 /*                                                                           */
   5 /*                          Optimize test sequences                          */
   6 /*                                                                           */
   7 /*                                                                           */
   8 /*                                                                           */
   9 /* (C) 2001-2012, Ullrich von Bassewitz                                      */
  10 /*                Roemerstrasse 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 /* cc65 */
  37 #include "codeent.h"
  38 #include "codeinfo.h"
  39 #include "copttest.h"
  40
  41
  42
  43 /*****************************************************************************/
  44 /*                              Optimize tests                               */
  45 /*****************************************************************************/
  46
  47
  48
  49 unsigned OptTest1 (CodeSeg* S)
  50 /* Given a sequence
  51 **
  52 **     stx     xxx
  53 **     ora     xxx
  54 **     beq/bne ...
  55 **
  56 ** If X is zero, the sequence may be changed to
  57 **
  58 **     cmp     #$00
  59 **     beq/bne ...
  60 **
  61 ** which may be optimized further by another step.
  62 **
  63 ** If A is zero, the sequence may be changed to
  64 **
  65 **     txa
  66 **     beq/bne ...
  67 */
  68 {
  69     unsigned Changes = 0;
  70     unsigned I;
  71
  72     /* Walk over the entries */
  73     I = 0;
  74     while (I < CS_GetEntryCount (S)) {
  75
  76         CodeEntry* L[3];
  77
  78         /* Get next entry */
  79         L[0] = CS_GetEntry (S, I);
  80
  81         /* Check if it's the sequence we're searching for */
  82         if (L[0]->OPC == OP65_STX              &&
  83             CS_GetEntries (S, L+1, I+1, 2)     &&
  84             !CE_HasLabel (L[1])                &&
  85             L[1]->OPC == OP65_ORA              &&
  86             strcmp (L[0]->Arg, L[1]->Arg) == 0 &&
  87             !CE_HasLabel (L[2])                &&
  88             (L[2]->Info & OF_ZBRA) != 0) {
  89
  90             /* Check if X is zero */
  91             if (L[0]->RI->In.RegX == 0) {
  92
  93                 /* Insert the compare */
  94                 CodeEntry* N = NewCodeEntry (OP65_CMP, AM65_IMM, "$00", 0, L[0]->LI);
  95                 CS_InsertEntry (S, N, I+2);
  96
  97                 /* Remove the two other insns */
  98                 CS_DelEntry (S, I+1);
  99                 CS_DelEntry (S, I);
 100
 101                 /* We had changes */
 102                 ++Changes;
 103
 104             /* Check if A is zero */
 105             } else if (L[1]->RI->In.RegA == 0) {
 106
 107                 /* Insert the txa */
 108                 CodeEntry* N = NewCodeEntry (OP65_TXA, AM65_IMP, 0, 0, L[1]->LI);
 109                 CS_InsertEntry (S, N, I+2);
 110
 111                 /* Remove the two other insns */
 112                 CS_DelEntry (S, I+1);
 113                 CS_DelEntry (S, I);
 114
 115                 /* We had changes */
 116                 ++Changes;
 117             }
 118         }
 119
 120         /* Next entry */
 121         ++I;
 122
 123     }
 124
 125     /* Return the number of changes made */
 126     return Changes;
 127 }
 128
 129
 130
 131 unsigned OptTest2 (CodeSeg* S)
 132 /* Search for an inc/dec operation followed by a load and a conditional
 133 ** branch based on the flags from the load. Remove the load if the insn
 134 ** isn't used later.
 135 */
 136 {
 137     unsigned Changes = 0;
 138
 139     /* Walk over the entries */
 140     unsigned I = 0;
 141     while (I < CS_GetEntryCount (S)) {
 142
 143         CodeEntry* L[3];
 144
 145         /* Get next entry */
 146         L[0] = CS_GetEntry (S, I);
 147
 148         /* Check if it's the sequence we're searching for */
 149         if ((L[0]->OPC == OP65_INC || L[0]->OPC == OP65_DEC)    &&
 150             CS_GetEntries (S, L+1, I+1, 2)                      &&
 151             !CE_HasLabel (L[1])                                 &&
 152             (L[1]->Info & OF_LOAD) != 0                         &&
 153             (L[2]->Info & OF_FBRA) != 0                         &&
 154             L[1]->AM == L[0]->AM                                &&
 155             strcmp (L[0]->Arg, L[1]->Arg) == 0                  &&
 156             (GetRegInfo (S, I+2, L[1]->Chg) & L[1]->Chg) == 0) {
 157
 158             /* Remove the load */
 159             CS_DelEntry (S, I+1);
 160              ++Changes;
 161         }
 162
 163         /* Next entry */
 164         ++I;
 165
 166     }
 167
 168     /* Return the number of changes made */
 169     return Changes;
 170 }