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

   1 /*****************************************************************************/
   2 /*                                                                           */
   3 /*                                coptpush.c                                 */
   4 /*                                                                           */
   5 /*                          Optimize push sequences                          */
   6 /*                                                                           */
   7 /*                                                                           */
   8 /*                                                                           */
   9 /* (C) 2001-2002 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 "coptpush.h"
  40
  41
  42
  43 /*****************************************************************************/
  44 /*                                   Code                                    */
  45 /*****************************************************************************/
  46
  47
  48
  49 unsigned OptPush1 (CodeSeg* S)
  50 /* Given a sequence
  51  *
  52  *     ldy     #xx
  53  *     jsr     ldaxysp
  54  *     jsr     pushax
  55  *
  56  * If a/x are not used later, replace that by
  57  *
  58  *     ldy     #xx+2
  59  *     jsr     pushwysp
  60  *
  61  * saving 3 bytes and several cycles.
  62  */
  63 {
  64     unsigned Changes = 0;
  65
  66     /* Walk over the entries */
  67     unsigned I = 0;
  68     while (I < CS_GetEntryCount (S)) {
  69
  70         CodeEntry* L[3];
  71
  72         /* Get next entry */
  73         L[0] = CS_GetEntry (S, I);
  74
  75         /* Check for the sequence */
  76         if (L[0]->OPC == OP65_LDY               &&
  77             CE_KnownImm (L[0])                  &&
  78             L[0]->Num < 0xFE                    &&
  79             !CS_RangeHasLabel (S, I+1, 2)       &&
  80             CS_GetEntries (S, L+1, I+1, 2)      &&
  81             CE_IsCall (L[1], "ldaxysp")         &&
  82             CE_IsCall (L[2], "pushax")          &&
  83             (GetRegInfo (S, I+3, REG_AX) & REG_AX) == 0) {
  84
  85             /* Insert new code behind the pushax */
  86             const char* Arg;
  87             CodeEntry* X;
  88
  89             /* ldy     #xx+1 */
  90             Arg = MakeHexArg (L[0]->Num+2);
  91             X = NewCodeEntry (OP65_LDY, AM65_IMM, Arg, 0, L[0]->LI);
  92             CS_InsertEntry (S, X, I+3);
  93
  94             /* jsr pushwysp */
  95             X = NewCodeEntry (OP65_JSR, AM65_ABS, "pushwysp", 0, L[2]->LI);
  96             CS_InsertEntry (S, X, I+4);
  97
  98             /* Delete the old code */
  99             CS_DelEntries (S, I, 3);
 100
 101             /* Remember, we had changes */
 102             ++Changes;
 103
 104         }
 105
 106         /* Next entry */
 107         ++I;
 108
 109     }
 110
 111     /* Return the number of changes made */
 112     return Changes;
 113 }
 114
 115
 116