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 #include <string.h>
  37
  38 /* cc65 */
  39 #include "codeent.h"
  40 #include "codeinfo.h"
  41 #include "copttest.h"
  42
  43
  44
  45 /*****************************************************************************/
  46 /*                              Optimize tests                               */
  47 /*****************************************************************************/
  48
  49
  50
  51 unsigned OptTest1 (CodeSeg* S)
  52 /* Given a sequence
  53  *
  54  *     stx     xxx
  55  *     ora     xxx
  56  *     beq/bne ...
  57  *
  58  * If X is zero, the sequence may be changed to
  59  *
  60  *     cmp     #$00
  61  *     beq/bne ...
  62  *
  63  * which may be optimized further by another step.
  64  *
  65  * If A is zero, the sequence may be changed to
  66  *
  67  *     txa
  68  *     beq/bne ...
  69  *
  70  */
  71 {
  72     unsigned Changes = 0;
  73     unsigned I;
  74
  75     /* Generate register info for this step */
  76     CS_GenRegInfo (S);
  77
  78     /* Walk over the entries */
  79     I = 0;
  80     while (I < CS_GetEntryCount (S)) {
  81
  82         CodeEntry* L[3];
  83
  84         /* Get next entry */
  85         L[0] = CS_GetEntry (S, I);
  86
  87         /* Check if it's the sequence we're searching for */
  88         if (L[0]->OPC == OP65_STX              &&
  89             CS_GetEntries (S, L+1, I+1, 2)     &&
  90             !CE_HasLabel (L[1])                &&
  91             L[1]->OPC == OP65_ORA              &&
  92             strcmp (L[0]->Arg, L[1]->Arg) == 0 &&
  93             !CE_HasLabel (L[2])                &&
  94             (L[2]->Info & OF_ZBRA) != 0) {
  95
  96             /* Check if X is zero */
  97             if (L[0]->RI->In.RegX == 0) {
  98
  99                 /* Insert the compare */
 100                 CodeEntry* N = NewCodeEntry (OP65_CMP, AM65_IMM, "$00", 0, L[0]->LI);
 101                 CS_InsertEntry (S, N, I+2);
 102
 103                 /* Remove the two other insns */
 104                 CS_DelEntry (S, I+1);
 105                 CS_DelEntry (S, I);
 106
 107                 /* We had changes */
 108                 ++Changes;
 109
 110             /* Check if A is zero */
 111             } else if (L[1]->RI->In.RegA == 0) {
 112
 113                 /* Insert the txa */
 114                 CodeEntry* N = NewCodeEntry (OP65_TXA, AM65_IMP, 0, 0, L[1]->LI);
 115                 CS_InsertEntry (S, N, I+2);
 116
 117                 /* Remove the two other insns */
 118                 CS_DelEntry (S, I+1);
 119                 CS_DelEntry (S, I);
 120
 121                 /* We had changes */
 122                 ++Changes;
 123             }
 124         }
 125
 126         /* Next entry */
 127         ++I;
 128
 129     }
 130
 131     /* Free register info */
 132     CS_FreeRegInfo (S);
 133
 134     /* Return the number of changes made */
 135     return Changes;
 136 }
 137
 138
 139