git.sur5r.net Git - cc65/blob - src/cc65/coptcmp.h

   1 /*****************************************************************************/
   2 /*                                                                           */
   3 /*                                 coptcmp.h                                 */
   4 /*                                                                           */
   5 /*                             Optimize compares                             */
   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 #ifndef COPTCMP_H
  37 #define COPTCMP_H
  38
  39
  40
  41 /* cc65 */
  42 #include "codeseg.h"
  43
  44
  45
  46 /*****************************************************************************/
  47 /*             Remove calls to the bool transformer subroutines              */
  48 /*****************************************************************************/
  49
  50
  51
  52 unsigned OptBoolTrans (CodeSeg* S);
  53 /* Try to remove the call to boolean transformer routines where the call is
  54  * not really needed.
  55  */
  56
  57
  58
  59 /*****************************************************************************/
  60 /*                        Optimizations for compares                         */
  61 /*****************************************************************************/
  62
  63
  64
  65 unsigned OptCmp1 (CodeSeg* S);
  66 /* Search for the sequence
  67  *
  68  *      stx     xx
  69  *      stx     tmp1
  70  *      ora     tmp1
  71  *
  72  * and replace it by
  73  *
  74  *      stx     xx
  75  *      ora     xx
  76  */
  77
  78 unsigned OptCmp2 (CodeSeg* S);
  79 /* Search for
  80  *
  81  *      lda/and/ora/eor ...
  82  *      cmp #$00
  83  *      jeq/jne
  84  * or
  85  *      lda/and/ora/eor ...
  86  *      cmp #$00
  87  *      jsr boolxx
  88  *
  89  * and remove the cmp.
  90  */
  91
  92 unsigned OptCmp3 (CodeSeg* S);
  93 /* Search for
  94  *
  95  *      lda     x
  96  *      ldx     y
  97  *      cpx     #a
  98  *      bne     L1
  99  *      cmp     #b
 100  *      jne/jeq L2
 101  *
 102  * If a is zero, we may remove the compare. If a and b are both zero, we may
 103  * replace it by the sequence
 104  *
 105  *      lda     x
 106  *      ora     x+1
 107  *      jne/jeq ...
 108  *
 109  * L1 may be either the label at the branch instruction, or the target label
 110  * of this instruction.
 111  */
 112
 113 unsigned OptCmp4 (CodeSeg* S);
 114 /* Optimize compares of local variables:
 115  *
 116  *      ldy     #o
 117  *      lda     (sp),y
 118  *      tax
 119  *      dey
 120  *      lda     (sp),y
 121  *      cpx     #a
 122  *      bne     L1
 123  *      cmp     #b
 124  *      jne/jeq L2
 125  */
 126
 127 unsigned OptCmp5 (CodeSeg* S);
 128 /* Search for calls to compare subroutines followed by a conditional branch
 129  * and replace them by cheaper versions, since the branch means that the
 130  * boolean value returned by these routines is not needed (we may also check
 131  * that explicitly, but for the current code generator it is always true).
 132  */
 133
 134 unsigned OptCmp6 (CodeSeg* S);
 135 /* Search for a sequence ldx/txa/branch and remove the txa if A is not
 136  * used later.
 137  */
 138
 139 unsigned OptCmp7 (CodeSeg* S);
 140 /* Check for register compares where the contents of the register and therefore
 141  * the result of the compare is known.
 142  */
 143
 144
 145
 146 /* End of coptcmp.h */
 147
 148 #endif
 149
 150
 151