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

   1 /*****************************************************************************/
   2 /*                                                                           */
   3 /*                                 coptcmp.h                                 */
   4 /*                                                                           */
   5 /*                             Optimize compares                             */
   6 /*                                                                           */
   7 /*                                                                           */
   8 /*                                                                           */
   9 /* (C) 2001-2009, 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 #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 **      ldx     xx
  69 **      stx     tmp1
  70 **      ora     tmp1
  71 **
  72 ** and replace it by
  73 **
  74 **      ora     xx
  75 */
  76
  77 unsigned OptCmp2 (CodeSeg* S);
  78 /* Search for the sequence
  79 **
  80 **      stx     xx
  81 **      stx     tmp1
  82 **      ora     tmp1
  83 **
  84 ** and replace it by
  85 **
  86 **      stx     xx
  87 **      ora     xx
  88 */
  89
  90 unsigned OptCmp3 (CodeSeg* S);
  91 /* Search for
  92 **
  93 **      lda/and/ora/eor ...
  94 **      cmp #$00
  95 **      jeq/jne
  96 ** or
  97 **      lda/and/ora/eor ...
  98 **      cmp #$00
  99 **      jsr boolxx
 100 **
 101 ** and remove the cmp.
 102 */
 103
 104 unsigned OptCmp4 (CodeSeg* S);
 105 /* Search for
 106 **
 107 **      lda     x
 108 **      ldx     y
 109 **      cpx     #a
 110 **      bne     L1
 111 **      cmp     #b
 112 **      jne/jeq L2
 113 **
 114 ** If a is zero, we may remove the compare. If a and b are both zero, we may
 115 ** replace it by the sequence
 116 **
 117 **      lda     x
 118 **      ora     x+1
 119 **      jne/jeq ...
 120 **
 121 ** L1 may be either the label at the branch instruction, or the target label
 122 ** of this instruction.
 123 */
 124
 125 unsigned OptCmp5 (CodeSeg* S);
 126 /* Optimize compares of local variables:
 127 **
 128 **      ldy     #o
 129 **      lda     (sp),y
 130 **      tax
 131 **      dey
 132 **      lda     (sp),y
 133 **      cpx     #a
 134 **      bne     L1
 135 **      cmp     #b
 136 **      jne/jeq L2
 137 */
 138
 139 unsigned OptCmp6 (CodeSeg* S);
 140 /* Search for calls to compare subroutines followed by a conditional branch
 141 ** and replace them by cheaper versions, since the branch means that the
 142 ** boolean value returned by these routines is not needed (we may also check
 143 ** that explicitly, but for the current code generator it is always true).
 144 */
 145
 146 unsigned OptCmp7 (CodeSeg* S);
 147 /* Search for a sequence ldx/txa/branch and remove the txa if A is not
 148 ** used later.
 149 */
 150
 151 unsigned OptCmp8 (CodeSeg* S);
 152 /* Check for register compares where the contents of the register and therefore
 153 ** the result of the compare is known.
 154 */
 155
 156 unsigned OptCmp9 (CodeSeg* S);
 157 /* Search for the sequence
 158 **
 159 **    sbc       xx
 160 **    bvs/bvc   L
 161 **    eor       #$80
 162 ** L: asl       a
 163 **    bcc/bcs   somewhere
 164 **
 165 ** If A is not used later (which should be the case), we can branch on the N
 166 ** flag instead of the carry flag and remove the asl.
 167 */
 168
 169
 170
 171 /* End of coptcmp.h */
 172
 173 #endif