cpu/bcd.cc

   1 /////////////////////////////////////////////////////////////////////////
   2 // $Id: bcd.cc,v 1.17 2006/03/06 22:02:51 sshwarts Exp $
   3 /////////////////////////////////////////////////////////////////////////
   4 //
   5 //  Copyright (C) 2002  MandrakeSoft S.A.
   6 //
   7 //    MandrakeSoft S.A.
   8 //    43, rue d'Aboukir
   9 //    75002 Paris - France
  10 //    http://www.linux-mandrake.com/
  11 //    http://www.mandrakesoft.com/
  12 //
  13 //  This library is free software; you can redistribute it and/or
  14 //  modify it under the terms of the GNU Lesser General Public
  15 //  License as published by the Free Software Foundation; either
  16 //  version 2 of the License, or (at your option) any later version.
  17 //
  18 //  This library is distributed in the hope that it will be useful,
  19 //  but WITHOUT ANY WARRANTY; without even the implied warranty of
  20 //  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  21 //  Lesser General Public License for more details.
  22 //
  23 //  You should have received a copy of the GNU Lesser General Public
  24 //  License along with this library; if not, write to the Free Software
  25 //  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
  26
  27
  28 #define NEED_CPU_REG_SHORTCUTS 1
  29 #include "bochs.h"
  30 #include "cpu.h"
  31 #define LOG_THIS BX_CPU_THIS_PTR
  32
  33
  34 void BX_CPU_C::AAA(bxInstruction_c *)
  35 {
  36   /*
  37    *  Note: This instruction incorrectly documented in Intel's materials.
  38    *        The right description is:
  39    *
  40    *    IF (((AL and 0FH) > 9) or (AF==1)
  41    *    THEN
  42    *        IF CPU<286 THEN {  AL <- AL+6 }
  43    *                   ELSE {  AX <- AX+6 }
  44    *        AH <- AH+1
  45    *        CF <- 1
  46    *        AF <- 1
  47    *    ELSE
  48    *        CF <- 0
  49    *        AF <- 0
  50    *    ENDIF
  51    *    AL <- AL and 0Fh
  52    */
  53
  54   /* Validated against Intel Pentium family hardware. */
  55
  56   /* AAA affects the following flags: A,C */
  57
  58   if ( ((AL & 0x0f) > 9) || get_AF() )
  59   {
  60     AX = AX + 0x106;
  61     set_AF(1);
  62     set_CF(1);
  63   }
  64   else {
  65     set_AF(0);
  66     set_CF(0);
  67   }
  68
  69   AL = AL & 0x0f;
  70
  71   /* AAA affects also the following flags: Z,S,O,P */
  72   /* modification of the flags is undocumented */
  73
  74   /* The following behaviour seems to match the P6 and
  75      its derived processors. */
  76   set_OF(0);
  77   set_SF(0); /* sign is always 0 because bits 4-7 of AL are zeroed */
  78   set_ZF(AL == 0);
  79   set_PF_base(AL);
  80 }
  81
  82 void BX_CPU_C::AAS(bxInstruction_c *)
  83 {
  84   /* AAS affects the following flags: A,C */
  85
  86   if ( ((AL & 0x0F) > 0x09) || get_AF() )
  87   {
  88     AX = AX - 0x106;
  89     set_AF(1);
  90     set_CF(1);
  91   }
  92   else {
  93     set_CF(0);
  94     set_AF(0);
  95   }
  96
  97   AL = AL & 0x0f;
  98
  99   /* AAS affects also the following flags: Z,S,O,P */
 100   /* modification of the flags is undocumented */
 101
 102   /* The following behaviour seems to match the P6 and
 103      its derived processors. */
 104   set_OF(0);
 105   set_SF(0); /* sign is always 0 because bits 4-7 of AL are zeroed */
 106   set_ZF(AL == 0);
 107   set_PF_base(AL);
 108 }
 109
 110 void BX_CPU_C::AAM(bxInstruction_c *i)
 111 {
 112   Bit8u al, imm8 = i->Ib();
 113
 114   if (imm8 == 0)
 115     exception(BX_DE_EXCEPTION, 0, 0);
 116
 117   al = AL;
 118   AH = al / imm8;
 119   AL = al % imm8;
 120
 121   /* AAM effects the following flags: A,C,O,S,Z,P */
 122   /* modification of flags A,C,O is undocumented */
 123
 124   /* The following behaviour seems to match the P6 and
 125      its derived processors. */
 126   clear_OF();   /* undocumented flag modification */
 127   clear_AF();
 128   clear_CF();
 129
 130   /* AAM affects the following flags: S,Z,P */
 131   set_SF(AL >= 0x80);
 132   set_ZF(AL == 0);
 133   set_PF_base(AL);
 134 }
 135
 136 void BX_CPU_C::AAD(bxInstruction_c *i)
 137 {
 138   Bit8u imm8 = i->Ib();
 139
 140   Bit16u tmp = AH;
 141   tmp *= imm8;
 142   tmp += AL;
 143
 144   AL = tmp & 0xff;
 145   AH = 0;
 146
 147   /* AAD effects the following flags: A,C,O,S,Z,P */
 148   /* modification of flags A,C,O is undocumented */
 149
 150   /* The following behaviour seems to match the P6 and
 151      its derived processors. */
 152   clear_OF();   /* undocumented flag modification */
 153   clear_AF();
 154   clear_CF();
 155
 156   set_SF(AL >= 0x80);
 157   set_ZF(AL == 0);
 158   set_PF_base(AL);
 159 }
 160
 161 void BX_CPU_C::DAA(bxInstruction_c *)
 162 {
 163   Bit8u tmpAL = AL;
 164   int   tmpCF = 0;
 165
 166   /* Validated against Intel Pentium family hardware. */
 167
 168   // DAA affects the following flags: S,Z,A,P,C
 169
 170   if (((tmpAL & 0x0F) > 0x09) || get_AF())
 171   {
 172     tmpCF = ((AL > 0xF9) || get_CF());
 173     AL = AL + 0x06;
 174     set_AF(1);
 175   }
 176   else
 177     set_AF(0);
 178
 179   if ((tmpAL > 0x99) || get_CF())
 180   {
 181     AL = AL + 0x60;
 182     tmpCF = 1;
 183   }
 184   else
 185     tmpCF = 0;
 186
 187   set_OF(0);    /* undocumented flag modification */
 188   set_SF(AL >= 0x80);
 189   set_ZF(AL==0);
 190   set_PF_base(AL);
 191   set_CF(tmpCF);
 192 }
 193
 194 void BX_CPU_C::DAS(bxInstruction_c *)
 195 {
 196   /* The algorithm for DAS is fashioned after the pseudo code in the
 197    * Pentium Processor Family Developer's Manual, volume 3.  It seems
 198    * to have changed from earlier processor's manuals.  I'm not sure
 199    * if this is a correction in the algorithm printed, or Intel has
 200    * changed the handling of instruction. Validated against Intel
 201    * Pentium family hardware.
 202    */
 203
 204   Bit8u tmpAL = AL;
 205   int tmpCF = 0;
 206
 207   /* DAS effect the following flags: A,C,S,Z,P */
 208
 209   if (((tmpAL & 0x0F) > 0x09) || get_AF())
 210   {
 211     tmpCF = (AL < 0x06) || get_CF();
 212     AL = AL - 0x06;
 213     set_AF(1);
 214   }
 215   else
 216     set_AF(0);
 217
 218   if ((tmpAL > 0x99) || get_CF())
 219   {
 220     AL = AL - 0x60;
 221     tmpCF = 1;
 222   }
 223
 224   set_OF(0);    /* undocumented flag modification */
 225   set_SF(AL >= 0x80);
 226   set_ZF(AL==0);
 227   set_PF_base(AL);
 228   set_CF(tmpCF);
 229 }