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      Ullrich von Bassewitz                                       */
  10 /*               Wacholderweg 14                                             */
  11 /*               D-70597 Stuttgart                                           */
  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 {
  70     unsigned Changes = 0;
  71     unsigned I;
  72
  73     /* Generate register info for this step */
  74     CS_GenRegInfo (S);
  75
  76     /* Walk over the entries */
  77     I = 0;
  78     while (I < CS_GetEntryCount (S)) {
  79
  80         CodeEntry* L[3];
  81
  82         /* Get next entry */
  83         L[0] = CS_GetEntry (S, I);
  84
  85         /* Check if it's the sequence we're searching for */
  86         if (L[0]->OPC == OP65_STX              &&
  87             CS_GetEntries (S, L+1, I+1, 2)     &&
  88             !CE_HasLabel (L[1])                &&
  89             L[1]->OPC == OP65_ORA              &&
  90             strcmp (L[0]->Arg, L[1]->Arg) == 0 &&
  91             !CE_HasLabel (L[2])                &&
  92             (L[2]->Info & OF_ZBRA) != 0) {
  93
  94             /* Check if X is zero */
  95             if (L[0]->RI->In.RegX == 0) {
  96
  97                 /* Insert the compare */
  98                 CodeEntry* N = NewCodeEntry (OP65_CMP, AM65_IMM, "$00", 0, L[0]->LI);
  99                 CS_InsertEntry (S, N, I+2);
 100
 101                 /* Remove the two other insns */
 102                 CS_DelEntry (S, I+1);
 103                 CS_DelEntry (S, I);
 104
 105                 /* We had changes */
 106                 ++Changes;
 107
 108             /* Check if A is zero */
 109             } else if (L[1]->RI->In.RegA == 0) {
 110
 111                 /* Insert the txa */
 112                 CodeEntry* N = NewCodeEntry (OP65_TXA, AM65_IMP, 0, 0, L[1]->LI);
 113                 CS_InsertEntry (S, N, I+2);
 114
 115                 /* Remove the two other insns */
 116                 CS_DelEntry (S, I+1);
 117                 CS_DelEntry (S, I);
 118
 119                 /* We had changes */
 120                 ++Changes;
 121             }
 122         }
 123
 124         /* Next entry */
 125         ++I;
 126
 127     }
 128
 129     /* Free register info */
 130     CS_FreeRegInfo (S);
 131
 132     /* Return the number of changes made */
 133     return Changes;
 134 }
 135
 136
 137