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

   1 /*****************************************************************************/
   2 /*                                                                           */
   3 /*                                codeinfo.c                                 */
   4 /*                                                                           */
   5 /*                  Additional information about 6502 code                   */
   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 #include <stdlib.h>
  37 #include <string.h>
  38
  39 /* common */
  40 #include "coll.h"
  41
  42 /* cc65 */
  43 #include "codeent.h"
  44 #include "codeseg.h"
  45 #include "datatype.h"
  46 #include "error.h"
  47 #include "reginfo.h"
  48 #include "symtab.h"
  49 #include "codeinfo.h"
  50
  51
  52
  53 /*****************************************************************************/
  54 /*                                   Data                                    */
  55 /*****************************************************************************/
  56
  57
  58
  59 /* Table listing the function names and code info values for known internally
  60  * used functions. This table should get auto-generated in the future.
  61  */
  62 typedef struct FuncInfo FuncInfo;
  63 struct FuncInfo {
  64     const char*     Name;       /* Function name */
  65     unsigned short  Use;        /* Register usage */
  66     unsigned short  Chg;        /* Changed/destroyed registers */
  67 };
  68
  69 static const FuncInfo FuncInfoTable[] = {
  70     { "addysp",         REG_Y,                REG_NONE                       },
  71     { "aslax1",         REG_AX,               REG_AX | REG_TMP1              },
  72     { "aslax2",         REG_AX,               REG_AX | REG_TMP1              },
  73     { "aslax3",         REG_AX,               REG_AX | REG_TMP1              },
  74     { "aslax4",         REG_AX,               REG_AX | REG_TMP1              },
  75     { "bnega",          REG_A,                REG_AX                         },
  76     { "bnegax",         REG_AX,               REG_AX                         },
  77     { "bnegeax",        REG_EAX,              REG_EAX                        },
  78     { "booleq",         REG_NONE,             REG_AX                         },
  79     { "boolge",         REG_NONE,             REG_AX                         },
  80     { "boolgt",         REG_NONE,             REG_AX                         },
  81     { "boolle",         REG_NONE,             REG_AX                         },
  82     { "boollt",         REG_NONE,             REG_AX                         },
  83     { "boolne",         REG_NONE,             REG_AX                         },
  84     { "booluge",        REG_NONE,             REG_AX                         },
  85     { "boolugt",        REG_NONE,             REG_AX                         },
  86     { "boolule",        REG_NONE,             REG_AX                         },
  87     { "boolult",        REG_NONE,             REG_AX                         },
  88     { "complax",        REG_AX,               REG_AX                         },
  89     { "decax1",         REG_AX,               REG_AX                         },
  90     { "decax2",         REG_AX,               REG_AX                         },
  91     { "decax3",         REG_AX,               REG_AX                         },
  92     { "decax4",         REG_AX,               REG_AX                         },
  93     { "decax5",         REG_AX,               REG_AX                         },
  94     { "decax6",         REG_AX,               REG_AX                         },
  95     { "decax7",         REG_AX,               REG_AX                         },
  96     { "decax8",         REG_AX,               REG_AX                         },
  97     { "decaxy",         REG_AXY,              REG_AX | REG_TMP1              },
  98     { "deceaxy",        REG_EAXY,             REG_EAX                        },
  99     { "decsp1",         REG_NONE,             REG_Y                          },
 100     { "decsp2",         REG_NONE,             REG_A                          },
 101     { "decsp3",         REG_NONE,             REG_A                          },
 102     { "decsp4",         REG_NONE,             REG_A                          },
 103     { "decsp5",         REG_NONE,             REG_A                          },
 104     { "decsp6",         REG_NONE,             REG_A                          },
 105     { "decsp7",         REG_NONE,             REG_A                          },
 106     { "decsp8",         REG_NONE,             REG_A                          },
 107     { "incax1",         REG_AX,               REG_AX                         },
 108     { "incax2",         REG_AX,               REG_AX                         },
 109     { "incsp1",         REG_NONE,             REG_NONE                       },
 110     { "incsp2",         REG_NONE,             REG_Y                          },
 111     { "incsp3",         REG_NONE,             REG_Y                          },
 112     { "incsp4",         REG_NONE,             REG_Y                          },
 113     { "incsp5",         REG_NONE,             REG_Y                          },
 114     { "incsp6",         REG_NONE,             REG_Y                          },
 115     { "incsp7",         REG_NONE,             REG_Y                          },
 116     { "incsp8",         REG_NONE,             REG_Y                          },
 117     { "laddeq",         REG_EAXY|REG_PTR1_LO, REG_EAXY | REG_PTR1_HI         },
 118     { "laddeq1",        REG_Y | REG_PTR1_LO,  REG_EAXY | REG_PTR1_HI         },
 119     { "laddeqa",        REG_AY | REG_PTR1_LO, REG_EAXY | REG_PTR1_HI         },
 120     { "ldaidx",         REG_AXY,              REG_AX | REG_PTR1              },
 121     { "ldauidx",        REG_AXY,              REG_AX | REG_PTR1              },
 122     { "ldax0sp",        REG_Y,                REG_AX                         },
 123     { "ldaxi",          REG_AX,               REG_AXY | REG_PTR1             },
 124     { "ldaxidx",        REG_AXY,              REG_AXY | REG_PTR1             },
 125     { "ldaxysp",        REG_Y,                REG_AXY                        },
 126     { "leaasp",         REG_A,                REG_AX                         },
 127     { "lsubeq",         REG_EAXY|REG_PTR1_LO, REG_EAXY | REG_PTR1_HI         },
 128     { "lsubeq0sp",      REG_EAX,              REG_EAXY                       },
 129     { "lsubeq1",        REG_Y | REG_PTR1_LO,  REG_EAXY | REG_PTR1_HI         },
 130     { "lsubeqa",        REG_AY | REG_PTR1_LO, REG_EAXY | REG_PTR1_HI         },
 131     { "lsubeqysp",      REG_EAXY,             REG_EAXY                       },
 132     { "negax",          REG_AX,               REG_AX                         },
 133     { "pusha",          REG_A,                REG_Y                          },
 134     { "pusha0",         REG_A,                REG_XY                         },
 135     { "pushax",         REG_AX,               REG_Y                          },
 136     { "pusheax",        REG_EAX,              REG_Y                          },
 137     { "pushw0sp",       REG_NONE,             REG_AXY                        },
 138     { "pushwysp",       REG_Y,                REG_AXY                        },
 139     { "shlax1",         REG_AX,               REG_AX | REG_TMP1              },
 140     { "shlax2",         REG_AX,               REG_AX | REG_TMP1              },
 141     { "shlax3",         REG_AX,               REG_AX | REG_TMP1              },
 142     { "shlax4",         REG_AX,               REG_AX | REG_TMP1              },
 143     { "shrax1",         REG_AX,               REG_AX | REG_TMP1              },
 144     { "shrax2",         REG_AX,               REG_AX | REG_TMP1              },
 145     { "shrax3",         REG_AX,               REG_AX | REG_TMP1              },
 146     { "shrax4",         REG_AX,               REG_AX | REG_TMP1              },
 147     { "shreax1",        REG_EAX,              REG_AX | REG_TMP1              },
 148     { "shreax2",        REG_EAX,              REG_AX | REG_TMP1              },
 149     { "shreax3",        REG_EAX,              REG_AX | REG_TMP1              },
 150     { "shreax4",        REG_EAX,              REG_AX | REG_TMP1              },
 151     { "staspidx",       REG_A | REG_Y,        REG_Y | REG_TMP1 | REG_PTR1    },
 152     { "stax0sp",        REG_AX,               REG_Y                          },
 153     { "staxysp",        REG_AXY,              REG_Y                          },
 154     { "subeq0sp",       REG_AX,               REG_AXY                        },
 155     { "subeqysp",       REG_AXY,              REG_AXY                        },
 156     { "tsteax",         REG_EAX,              REG_Y                          },
 157     { "tosadda0",       REG_A,                REG_AXY                        },
 158     { "tosaddax",       REG_AX,               REG_AXY                        },
 159     { "tosicmp",        REG_AX,               REG_AXY | REG_SREG             },
 160     { "tosdiva0",       REG_AX,               REG_ALL                        },
 161     { "tosdivax",       REG_AX,               REG_ALL                        },
 162     { "tosdiveax",      REG_EAX,              REG_ALL                        },
 163     { "toseqeax",       REG_EAX,              REG_AXY | REG_PTR1             },
 164     { "tosgeeax",       REG_EAX,              REG_AXY | REG_PTR1             },
 165     { "tosgteax",       REG_EAX,              REG_AXY | REG_PTR1             },
 166     { "toslcmp",        REG_EAX,              REG_A | REG_Y | REG_PTR1       },
 167     { "tosleeax",       REG_EAX,              REG_AXY | REG_PTR1             },
 168     { "toslteax",       REG_EAX,              REG_AXY | REG_PTR1             },
 169     { "tosmula0",       REG_AX,               REG_ALL                        },
 170     { "tosmulax",       REG_AX,               REG_ALL                        },
 171     { "tosmuleax",      REG_EAX,              REG_ALL                        },
 172     { "tosneeax",       REG_EAX,              REG_AXY | REG_PTR1             },
 173     { "tosshreax",      REG_EAX,              REG_EAXY | REG_PTR1 | REG_PTR2 },
 174     { "tossuba0",       REG_A,                REG_AXY                        },
 175     { "tossubax",       REG_AX,               REG_AXY                        },
 176     { "tossubeax",      REG_EAX,              REG_EAXY                       },
 177     { "tosugeeax",      REG_EAX,              REG_AXY | REG_PTR1             },
 178     { "tosugteax",      REG_EAX,              REG_AXY | REG_PTR1             },
 179     { "tosuleeax",      REG_EAX,              REG_AXY | REG_PTR1             },
 180     { "tosulteax",      REG_EAX,              REG_AXY | REG_PTR1             },
 181     { "tosumula0",      REG_AX,               REG_ALL                        },
 182     { "tosumulax",      REG_AX,               REG_ALL                        },
 183     { "tosumuleax",     REG_EAX,              REG_ALL                        },
 184     { "utsteax",        REG_EAX,              REG_Y                          },
 185 };
 186 #define FuncInfoCount   (sizeof(FuncInfoTable) / sizeof(FuncInfoTable[0]))
 187
 188 /* Table with names of zero page locations used by the compiler */
 189 static const ZPInfo ZPInfoTable[] = {
 190     {   0, "ptr1",      REG_PTR1_LO,    REG_PTR1        },
 191     {   0, "ptr1+1",    REG_PTR1_HI,    REG_PTR1        },
 192     {   0, "ptr2",      REG_PTR2_LO,    REG_PTR2        },
 193     {   0, "ptr2+1",    REG_PTR2_HI,    REG_PTR2        },
 194     {   4, "ptr3",      REG_NONE,       REG_NONE        },
 195     {   4, "ptr4",      REG_NONE,       REG_NONE        },
 196     {   7, "regbank",   REG_NONE,       REG_NONE        },
 197     {   0, "regsave",   REG_SAVE_LO,    REG_SAVE        },
 198     {   0, "regsave+1", REG_SAVE_HI,    REG_SAVE        },
 199     {   0, "sp",        REG_SP_LO,      REG_SP          },
 200     {   0, "sp+1",      REG_SP_HI,      REG_SP          },
 201     {   0, "sreg",      REG_SREG_LO,    REG_SREG        },
 202     {   0, "sreg+1",    REG_SREG_HI,    REG_SREG        },
 203     {   0, "tmp1",      REG_TMP1,       REG_TMP1        },
 204     {   0, "tmp2",      REG_NONE,       REG_NONE        },
 205     {   0, "tmp3",      REG_NONE,       REG_NONE        },
 206     {   0, "tmp4",      REG_NONE,       REG_NONE        },
 207 };
 208 #define ZPInfoCount     (sizeof(ZPInfoTable) / sizeof(ZPInfoTable[0]))
 209
 210
 211
 212 /*****************************************************************************/
 213 /*                                   Code                                    */
 214 /*****************************************************************************/
 215
 216
 217
 218 static int CompareFuncInfo (const void* Key, const void* Info)
 219 /* Compare function for bsearch */
 220 {
 221     return strcmp (Key, ((const FuncInfo*) Info)->Name);
 222 }
 223
 224
 225
 226 void GetFuncInfo (const char* Name, unsigned short* Use, unsigned short* Chg)
 227 /* For the given function, lookup register information and store it into
 228  * the given variables. If the function is unknown, assume it will use and
 229  * load all registers.
 230  */
 231 {
 232     /* If the function name starts with an underline, it is an external
 233      * function. Search for it in the symbol table. If the function does
 234      * not start with an underline, it may be a runtime support function.
 235      * Search for it in the list of builtin functions.
 236      */
 237     if (Name[0] == '_') {
 238
 239         /* Search in the symbol table, skip the leading underscore */
 240         SymEntry* E = FindGlobalSym (Name+1);
 241
 242         /* Did we find it in the top level table? */
 243         if (E && IsTypeFunc (E->Type)) {
 244
 245             /* A function may use the A or A/X registers if it is a fastcall
 246              * function. If it is not a fastcall function but a variadic one,
 247              * it will use the Y register (the parameter size is passed here).
 248              * In all other cases, no registers are used. However, we assume
 249              * that any function will destroy all registers.
 250              */
 251             FuncDesc* D = E->V.F.Func;
 252             if ((D->Flags & FD_FASTCALL) != 0 && D->ParamCount > 0) {
 253                 /* Will use registers depending on the last param */
 254                 SymEntry* LastParam = D->SymTab->SymTail;
 255                 unsigned LastParamSize = CheckedSizeOf (LastParam->Type);
 256                 if (LastParamSize == 1) {
 257                     *Use = REG_A;
 258                 } else if (LastParamSize == 2) {
 259                     *Use = REG_AX;
 260                 } else {
 261                     *Use = REG_EAX;
 262                 }
 263             } else if ((D->Flags & FD_VARIADIC) != 0) {
 264                 *Use = REG_Y;
 265             } else {
 266                 /* Will not use any registers */
 267                 *Use = REG_NONE;
 268             }
 269
 270             /* Will destroy all registers */
 271             *Chg = REG_ALL;
 272
 273             /* Done */
 274             return;
 275         }
 276
 277     } else {
 278
 279         /* Search for the function in the list of builtin functions */
 280         const FuncInfo* Info = bsearch (Name, FuncInfoTable, FuncInfoCount,
 281                                         sizeof(FuncInfo), CompareFuncInfo);
 282
 283         /* Do we know the function? */
 284         if (Info) {
 285             /* Use the information we have */
 286             *Use = Info->Use;
 287             *Chg = Info->Chg;
 288             return;
 289         }
 290     }
 291
 292     /* Function not found - assume that the primary register is input, and all
 293      * registers are changed
 294      */
 295     *Use = REG_EAXY;
 296     *Chg = REG_ALL;
 297 }
 298
 299
 300
 301 static int CompareZPInfo (const void* Name, const void* Info)
 302 /* Compare function for bsearch */
 303 {
 304     /* Cast the pointers to the correct data type */
 305     const char* N   = (const char*) Name;
 306     const ZPInfo* E = (const ZPInfo*) Info;
 307
 308     /* Do the compare. Be careful because of the length (Info may contain
 309      * more than just the zeropage name).
 310      */
 311     if (E->Len == 0) {
 312         /* Do a full compare */
 313         return strcmp (N, E->Name);
 314     } else {
 315         /* Only compare the first part */
 316         int Res = strncmp (N, E->Name, E->Len);
 317         if (Res == 0 && (N[E->Len] != '\0' && N[E->Len] != '+')) {
 318             /* Name is actually longer than Info->Name */
 319             Res = -1;
 320         }
 321         return Res;
 322     }
 323 }
 324
 325
 326
 327 const ZPInfo* GetZPInfo (const char* Name)
 328 /* If the given name is a zero page symbol, return a pointer to the info
 329  * struct for this symbol, otherwise return NULL.
 330  */
 331 {
 332     /* Search for the zp location in the list */
 333     return bsearch (Name, ZPInfoTable, ZPInfoCount,
 334                     sizeof(ZPInfo), CompareZPInfo);
 335 }
 336
 337
 338
 339 static unsigned GetRegInfo2 (CodeSeg* S,
 340                              CodeEntry* E,
 341                              int Index,
 342                              Collection* Visited,
 343                              unsigned Used,
 344                              unsigned Unused,
 345                              unsigned Wanted)
 346 /* Recursively called subfunction for GetRegInfo. */
 347 {
 348     /* Follow the instruction flow recording register usage. */
 349     while (1) {
 350
 351         unsigned R;
 352
 353         /* Check if we have already visited the current code entry. If so,
 354          * bail out.
 355          */
 356         if (CE_HasMark (E)) {
 357             break;
 358         }
 359
 360         /* Mark this entry as already visited */
 361         CE_SetMark (E);
 362         CollAppend (Visited, E);
 363
 364         /* Evaluate the used registers */
 365         R = E->Use;
 366         if (E->OPC == OP65_RTS ||
 367             ((E->Info & OF_BRA) != 0 && E->JumpTo == 0)) {
 368             /* This instruction will leave the function */
 369             R |= S->ExitRegs;
 370         }
 371         if (R != REG_NONE) {
 372             /* We are not interested in the use of any register that has been
 373              * used before.
 374              */
 375             R &= ~Unused;
 376             /* Remember the remaining registers */
 377             Used |= R;
 378         }
 379
 380         /* Evaluate the changed registers */
 381         if ((R = E->Chg) != REG_NONE) {
 382             /* We are not interested in the use of any register that has been
 383              * used before.
 384              */
 385             R &= ~Used;
 386             /* Remember the remaining registers */
 387             Unused |= R;
 388         }
 389
 390         /* If we know about all registers now, bail out */
 391         if (((Used | Unused) & Wanted) == Wanted) {
 392             break;
 393         }
 394
 395         /* If the instruction is an RTS or RTI, we're done */
 396         if ((E->Info & OF_RET) != 0) {
 397             break;
 398         }
 399
 400         /* If we have an unconditional branch, follow this branch if possible,
 401          * otherwise we're done.
 402          */
 403         if ((E->Info & OF_UBRA) != 0) {
 404
 405             /* Does this jump have a valid target? */
 406             if (E->JumpTo) {
 407
 408                 /* Unconditional jump */
 409                 E     = E->JumpTo->Owner;
 410                 Index = -1;             /* Invalidate */
 411
 412             } else {
 413                 /* Jump outside means we're done */
 414                 break;
 415             }
 416
 417         /* In case of conditional branches, follow the branch if possible and
 418          * follow the normal flow (branch not taken) afterwards. If we cannot
 419          * follow the branch, we're done.
 420          */
 421         } else if ((E->Info & OF_CBRA) != 0) {
 422
 423             if (E->JumpTo) {
 424
 425                 /* Recursively determine register usage at the branch target */
 426                 unsigned U1;
 427                 unsigned U2;
 428
 429                 U1 = GetRegInfo2 (S, E->JumpTo->Owner, -1, Visited, Used, Unused, Wanted);
 430                 if (U1 == REG_ALL) {
 431                     /* All registers used, no need for second call */
 432                     return REG_AXY;
 433                 }
 434                 if (Index < 0) {
 435                     Index = CS_GetEntryIndex (S, E);
 436                 }
 437                 if ((E = CS_GetEntry (S, ++Index)) == 0) {
 438                     Internal ("GetRegInfo2: No next entry!");
 439                 }
 440                 U2 = GetRegInfo2 (S, E, Index, Visited, Used, Unused, Wanted);
 441                 return U1 | U2;         /* Used in any of the branches */
 442
 443             } else {
 444                 /* Jump to global symbol */
 445                 break;
 446             }
 447
 448         } else {
 449
 450             /* Just go to the next instruction */
 451             if (Index < 0) {
 452                 Index = CS_GetEntryIndex (S, E);
 453             }
 454             E = CS_GetEntry (S, ++Index);
 455             if (E == 0) {
 456                 /* No next entry */
 457                 Internal ("GetRegInfo2: No next entry!");
 458             }
 459
 460         }
 461
 462     }
 463
 464     /* Return to the caller the complement of all unused registers */
 465     return Used;
 466 }
 467
 468
 469
 470 static unsigned GetRegInfo1 (CodeSeg* S,
 471                              CodeEntry* E,
 472                              int Index,
 473                              Collection* Visited,
 474                              unsigned Used,
 475                              unsigned Unused,
 476                              unsigned Wanted)
 477 /* Recursively called subfunction for GetRegInfo. */
 478 {
 479     /* Remember the current count of the line collection */
 480     unsigned Count = CollCount (Visited);
 481
 482     /* Call the worker routine */
 483     unsigned R = GetRegInfo2 (S, E, Index, Visited, Used, Unused, Wanted);
 484
 485     /* Restore the old count, unmarking all new entries */
 486     unsigned NewCount = CollCount (Visited);
 487     while (NewCount-- > Count) {
 488         CodeEntry* E = CollAt (Visited, NewCount);
 489         CE_ResetMark (E);
 490         CollDelete (Visited, NewCount);
 491     }
 492
 493     /* Return the registers used */
 494     return R;
 495 }
 496
 497
 498
 499 unsigned GetRegInfo (struct CodeSeg* S, unsigned Index, unsigned Wanted)
 500 /* Determine register usage information for the instructions starting at the
 501  * given index.
 502  */
 503 {
 504     CodeEntry*      E;
 505     Collection      Visited;    /* Visited entries */
 506     unsigned        R;
 507
 508     /* Get the code entry for the given index */
 509     if (Index >= CS_GetEntryCount (S)) {
 510         /* There is no such code entry */
 511         return REG_NONE;
 512     }
 513     E = CS_GetEntry (S, Index);
 514
 515     /* Initialize the data structure used to collection information */
 516     InitCollection (&Visited);
 517
 518     /* Call the recursive subfunction */
 519     R = GetRegInfo1 (S, E, Index, &Visited, REG_NONE, REG_NONE, Wanted);
 520
 521     /* Delete the line collection */
 522     DoneCollection (&Visited);
 523
 524     /* Return the registers used */
 525     return R;
 526 }
 527
 528
 529
 530 int RegAUsed (struct CodeSeg* S, unsigned Index)
 531 /* Check if the value in A is used. */
 532 {
 533     return (GetRegInfo (S, Index, REG_A) & REG_A) != 0;
 534 }
 535
 536
 537
 538 int RegXUsed (struct CodeSeg* S, unsigned Index)
 539 /* Check if the value in X is used. */
 540 {
 541     return (GetRegInfo (S, Index, REG_X) & REG_X) != 0;
 542 }
 543
 544
 545
 546 int RegYUsed (struct CodeSeg* S, unsigned Index)
 547 /* Check if the value in Y is used. */
 548 {
 549     return (GetRegInfo (S, Index, REG_Y) & REG_Y) != 0;
 550 }
 551
 552
 553
 554 int RegAXUsed (struct CodeSeg* S, unsigned Index)
 555 /* Check if the value in A or(!) the value in X are used. */
 556 {
 557     return (GetRegInfo (S, Index, REG_AX) & REG_AX) != 0;
 558 }
 559
 560
 561
 562 unsigned GetKnownReg (unsigned Use, const RegContents* RC)
 563 /* Return the register or zero page location from the set in Use, thats
 564  * contents are known. If Use does not contain any register, or if the
 565  * register in question does not have a known value, return REG_NONE.
 566  */
 567 {
 568     if ((Use & REG_A) != 0) {
 569         return (RC && RC->RegA >= 0)? REG_A : REG_NONE;
 570     } else if ((Use & REG_X) != 0) {
 571         return (RC && RC->RegX >= 0)? REG_X : REG_NONE;
 572     } else if ((Use & REG_Y) != 0) {
 573         return (RC && RC->RegY >= 0)? REG_Y : REG_NONE;
 574     } else if ((Use & REG_TMP1) != 0) {
 575         return (RC && RC->Tmp1 >= 0)? REG_TMP1 : REG_NONE;
 576     } else if ((Use & REG_SREG_LO) != 0) {
 577         return (RC && RC->SRegLo >= 0)? REG_SREG_LO : REG_NONE;
 578     } else if ((Use & REG_SREG_HI) != 0) {
 579         return (RC && RC->SRegHi >= 0)? REG_SREG_HI : REG_NONE;
 580     } else {
 581         return REG_NONE;
 582     }
 583 }
 584
 585
 586