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Annotation of gcc/rtlanal.c, revision 1.1

1.1     ! root        1: /* Analyze RTL for C-Compiler
        !             2:    Copyright (C) 1987, 1988, 1991 Free Software Foundation, Inc.
        !             3: 
        !             4: This file is part of GNU CC.
        !             5: 
        !             6: GNU CC is free software; you can redistribute it and/or modify
        !             7: it under the terms of the GNU General Public License as published by
        !             8: the Free Software Foundation; either version 2, or (at your option)
        !             9: any later version.
        !            10: 
        !            11: GNU CC is distributed in the hope that it will be useful,
        !            12: but WITHOUT ANY WARRANTY; without even the implied warranty of
        !            13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
        !            14: GNU General Public License for more details.
        !            15: 
        !            16: You should have received a copy of the GNU General Public License
        !            17: along with GNU CC; see the file COPYING.  If not, write to
        !            18: the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
        !            19: 
        !            20: 
        !            21: #include "config.h"
        !            22: #include "rtl.h"
        !            23: 
        !            24: void note_stores ();
        !            25: int reg_set_p ();
        !            26: 
        !            27: /* Bit flags that specify the machine subtype we are compiling for.
        !            28:    Bits are tested using macros TARGET_... defined in the tm.h file
        !            29:    and set by `-m...' switches.  Must be defined in rtlanal.c.  */
        !            30: 
        !            31: int target_flags;
        !            32: 
        !            33: /* Return 1 if the value of X is unstable
        !            34:    (would be different at a different point in the program).
        !            35:    The frame pointer, arg pointer, etc. are considered stable
        !            36:    (within one function) and so is anything marked `unchanging'.  */
        !            37: 
        !            38: int
        !            39: rtx_unstable_p (x)
        !            40:      rtx x;
        !            41: {
        !            42:   register RTX_CODE code = GET_CODE (x);
        !            43:   register int i;
        !            44:   register char *fmt;
        !            45: 
        !            46:   if (code == MEM)
        !            47:     return ! RTX_UNCHANGING_P (x);
        !            48: 
        !            49:   if (code == QUEUED)
        !            50:     return 1;
        !            51: 
        !            52:   if (code == CONST || code == CONST_INT)
        !            53:     return 0;
        !            54: 
        !            55:   if (code == REG)
        !            56:     return ! (REGNO (x) == FRAME_POINTER_REGNUM
        !            57:              || REGNO (x) == ARG_POINTER_REGNUM
        !            58:              || RTX_UNCHANGING_P (x));
        !            59: 
        !            60:   fmt = GET_RTX_FORMAT (code);
        !            61:   for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
        !            62:     if (fmt[i] == 'e')
        !            63:       if (rtx_unstable_p (XEXP (x, i)))
        !            64:        return 1;
        !            65:   return 0;
        !            66: }
        !            67: 
        !            68: /* Return 1 if X has a value that can vary even between two
        !            69:    executions of the program.  0 means X can be compared reliably
        !            70:    against certain constants or near-constants.
        !            71:    The frame pointer and the arg pointer are considered constant.  */
        !            72: 
        !            73: int
        !            74: rtx_varies_p (x)
        !            75:      rtx x;
        !            76: {
        !            77:   register RTX_CODE code = GET_CODE (x);
        !            78:   register int i;
        !            79:   register char *fmt;
        !            80: 
        !            81:   switch (code)
        !            82:     {
        !            83:     case MEM:
        !            84:     case QUEUED:
        !            85:       return 1;
        !            86: 
        !            87:     case CONST:
        !            88:     case CONST_INT:
        !            89:     case CONST_DOUBLE:
        !            90:     case SYMBOL_REF:
        !            91:     case LABEL_REF:
        !            92:       return 0;
        !            93: 
        !            94:     case REG:
        !            95:       /* Note that we have to test for the actual rtx used for the frame
        !            96:         and arg pointers and not just the register number in case we have
        !            97:         eliminated the frame and/or arg pointer and are using it
        !            98:         for pseudos.  */
        !            99:       return ! (x == frame_pointer_rtx || x == arg_pointer_rtx);
        !           100: 
        !           101:     case LO_SUM:
        !           102:       /* The operand 0 of a LO_SUM is considered constant
        !           103:         (in fact is it related specifically to operand 1).  */
        !           104:       return rtx_varies_p (XEXP (x, 1));
        !           105:     }
        !           106: 
        !           107:   fmt = GET_RTX_FORMAT (code);
        !           108:   for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
        !           109:     if (fmt[i] == 'e')
        !           110:       if (rtx_varies_p (XEXP (x, i)))
        !           111:        return 1;
        !           112:   return 0;
        !           113: }
        !           114: 
        !           115: /* Return 0 if the use of X as an address in a MEM can cause a trap.  */
        !           116: 
        !           117: int
        !           118: rtx_addr_can_trap_p (x)
        !           119:      register rtx x;
        !           120: {
        !           121:   register enum rtx_code code = GET_CODE (x);
        !           122: 
        !           123:   switch (code)
        !           124:     {
        !           125:     case SYMBOL_REF:
        !           126:     case LABEL_REF:
        !           127:       /* SYMBOL_REF is problematic due to the possible presence of
        !           128:         a #pragma weak, but to say that loads from symbols can trap is
        !           129:         *very* costly.  It's not at all clear what's best here.  For
        !           130:         now, we ignore the impact of #pragma weak.  */
        !           131:       return 0;
        !           132: 
        !           133:     case REG:
        !           134:       /* As in rtx_varies_p, we have to use the actual rtx, not reg number.  */
        !           135:       return ! (x == frame_pointer_rtx || x == stack_pointer_rtx
        !           136:                || x == arg_pointer_rtx);
        !           137: 
        !           138:     case CONST:
        !           139:       return rtx_addr_can_trap_p (XEXP (x, 0));
        !           140: 
        !           141:     case PLUS:
        !           142:       /* An address is assumed not to trap if it is an address that can't
        !           143:         trap plus a constant integer.  */
        !           144:       return (rtx_addr_can_trap_p (XEXP (x, 0))
        !           145:              || GET_CODE (XEXP (x, 1)) != CONST_INT);
        !           146: 
        !           147:     case LO_SUM:
        !           148:       return rtx_addr_can_trap_p (XEXP (x, 1));
        !           149:     }
        !           150: 
        !           151:   /* If it isn't one of the case above, it can cause a trap.  */
        !           152:   return 1;
        !           153: }
        !           154: 
        !           155: /* Return 1 if X refers to a memory location whose address 
        !           156:    cannot be compared reliably with constant addresses,
        !           157:    or if X refers to a BLKmode memory object.  */
        !           158: 
        !           159: int
        !           160: rtx_addr_varies_p (x)
        !           161:      rtx x;
        !           162: {
        !           163:   register enum rtx_code code;
        !           164:   register int i;
        !           165:   register char *fmt;
        !           166: 
        !           167:   if (x == 0)
        !           168:     return 0;
        !           169: 
        !           170:   code = GET_CODE (x);
        !           171:   if (code == MEM)
        !           172:     return GET_MODE (x) == BLKmode || rtx_varies_p (XEXP (x, 0));
        !           173: 
        !           174:   fmt = GET_RTX_FORMAT (code);
        !           175:   for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
        !           176:     if (fmt[i] == 'e')
        !           177:       if (rtx_addr_varies_p (XEXP (x, i)))
        !           178:        return 1;
        !           179:   return 0;
        !           180: }
        !           181: 
        !           182: /* Return the value of the integer term in X, if one is apparent;
        !           183:    otherwise return 0.
        !           184:    Only obvious integer terms are detected.
        !           185:    This is used in cse.c with the `related_value' field.*/
        !           186: 
        !           187: int
        !           188: get_integer_term (x)
        !           189:      rtx x;
        !           190: {
        !           191:   if (GET_CODE (x) == CONST)
        !           192:     x = XEXP (x, 0);
        !           193: 
        !           194:   if (GET_CODE (x) == MINUS
        !           195:       && GET_CODE (XEXP (x, 1)) == CONST_INT)
        !           196:     return - INTVAL (XEXP (x, 1));
        !           197:   if (GET_CODE (x) == PLUS
        !           198:       && GET_CODE (XEXP (x, 1)) == CONST_INT)
        !           199:     return INTVAL (XEXP (x, 1));
        !           200:   return 0;
        !           201: }
        !           202: 
        !           203: /* If X is a constant, return the value sans apparent integer term;
        !           204:    otherwise return 0.
        !           205:    Only obvious integer terms are detected.  */
        !           206: 
        !           207: rtx
        !           208: get_related_value (x)
        !           209:      rtx x;
        !           210: {
        !           211:   if (GET_CODE (x) != CONST)
        !           212:     return 0;
        !           213:   x = XEXP (x, 0);
        !           214:   if (GET_CODE (x) == PLUS
        !           215:       && GET_CODE (XEXP (x, 1)) == CONST_INT)
        !           216:     return XEXP (x, 0);
        !           217:   else if (GET_CODE (x) == MINUS
        !           218:           && GET_CODE (XEXP (x, 1)) == CONST_INT)
        !           219:     return XEXP (x, 0);
        !           220:   return 0;
        !           221: }
        !           222: 
        !           223: /* Nonzero if register REG appears somewhere within IN.
        !           224:    Also works if REG is not a register; in this case it checks
        !           225:    for a subexpression of IN that is Lisp "equal" to REG.  */
        !           226: 
        !           227: int
        !           228: reg_mentioned_p (reg, in)
        !           229:      register rtx reg, in;
        !           230: {
        !           231:   register char *fmt;
        !           232:   register int i;
        !           233:   register enum rtx_code code;
        !           234: 
        !           235:   if (in == 0)
        !           236:     return 0;
        !           237: 
        !           238:   if (reg == in)
        !           239:     return 1;
        !           240: 
        !           241:   if (GET_CODE (in) == LABEL_REF)
        !           242:     return reg == XEXP (in, 0);
        !           243: 
        !           244:   code = GET_CODE (in);
        !           245: 
        !           246:   switch (code)
        !           247:     {
        !           248:       /* Compare registers by number.  */
        !           249:     case REG:
        !           250:       return GET_CODE (reg) == REG && REGNO (in) == REGNO (reg);
        !           251: 
        !           252:       /* These codes have no constituent expressions
        !           253:         and are unique.  */
        !           254:     case SCRATCH:
        !           255:     case CC0:
        !           256:     case PC:
        !           257:       return 0;
        !           258: 
        !           259:     case CONST_INT:
        !           260:       return GET_CODE (reg) == CONST_INT && INTVAL (in) == INTVAL (reg);
        !           261:       
        !           262:     case CONST_DOUBLE:
        !           263:       /* These are kept unique for a given value.  */
        !           264:       return 0;
        !           265:     }
        !           266: 
        !           267:   if (GET_CODE (reg) == code && rtx_equal_p (reg, in))
        !           268:     return 1;
        !           269: 
        !           270:   fmt = GET_RTX_FORMAT (code);
        !           271: 
        !           272:   for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
        !           273:     {
        !           274:       if (fmt[i] == 'E')
        !           275:        {
        !           276:          register int j;
        !           277:          for (j = XVECLEN (in, i) - 1; j >= 0; j--)
        !           278:            if (reg_mentioned_p (reg, XVECEXP (in, i, j)))
        !           279:              return 1;
        !           280:        }
        !           281:       else if (fmt[i] == 'e'
        !           282:               && reg_mentioned_p (reg, XEXP (in, i)))
        !           283:        return 1;
        !           284:     }
        !           285:   return 0;
        !           286: }
        !           287: 
        !           288: /* Return 1 if in between BEG and END, exclusive of BEG and END, there is
        !           289:    no CODE_LABEL insn.  */
        !           290: 
        !           291: int
        !           292: no_labels_between_p (beg, end)
        !           293:      rtx beg, end;
        !           294: {
        !           295:   register rtx p;
        !           296:   for (p = NEXT_INSN (beg); p != end; p = NEXT_INSN (p))
        !           297:     if (GET_CODE (p) == CODE_LABEL)
        !           298:       return 0;
        !           299:   return 1;
        !           300: }
        !           301: 
        !           302: /* Nonzero if register REG is used in an insn between
        !           303:    FROM_INSN and TO_INSN (exclusive of those two).  */
        !           304: 
        !           305: int
        !           306: reg_used_between_p (reg, from_insn, to_insn)
        !           307:      rtx reg, from_insn, to_insn;
        !           308: {
        !           309:   register rtx insn;
        !           310: 
        !           311:   if (from_insn == to_insn)
        !           312:     return 0;
        !           313: 
        !           314:   for (insn = NEXT_INSN (from_insn); insn != to_insn; insn = NEXT_INSN (insn))
        !           315:     if (GET_RTX_CLASS (GET_CODE (insn)) == 'i'
        !           316:        && reg_overlap_mentioned_p (reg, PATTERN (insn)))
        !           317:       return 1;
        !           318:   return 0;
        !           319: }
        !           320: 
        !           321: /* Nonzero if the old value of X, a register, is referenced in BODY.  If X
        !           322:    is entirely replaced by a new value and the only use is as a SET_DEST,
        !           323:    we do not consider it a reference.  */
        !           324: 
        !           325: int
        !           326: reg_referenced_p (x, body)
        !           327:      rtx x;
        !           328:      rtx body;
        !           329: {
        !           330:   int i;
        !           331: 
        !           332:   switch (GET_CODE (body))
        !           333:     {
        !           334:     case SET:
        !           335:       if (reg_overlap_mentioned_p (x, SET_SRC (body)))
        !           336:        return 1;
        !           337: 
        !           338:       /* If the destination is anything other than CC0, PC, a REG or a SUBREG
        !           339:         of a REG that occupies all of the REG, the insn references X if
        !           340:         it is mentioned in the destination.  */
        !           341:       if (GET_CODE (SET_DEST (body)) != CC0
        !           342:          && GET_CODE (SET_DEST (body)) != PC
        !           343:          && GET_CODE (SET_DEST (body)) != REG
        !           344:          && ! (GET_CODE (SET_DEST (body)) == SUBREG
        !           345:                && GET_CODE (SUBREG_REG (SET_DEST (body))) == REG
        !           346:                && (((GET_MODE_SIZE (GET_MODE (SUBREG_REG (SET_DEST (body))))
        !           347:                      + (UNITS_PER_WORD - 1)) / UNITS_PER_WORD)
        !           348:                    == ((GET_MODE_SIZE (GET_MODE (SET_DEST (body)))
        !           349:                         + (UNITS_PER_WORD - 1)) / UNITS_PER_WORD)))
        !           350:          && reg_overlap_mentioned_p (x, SET_DEST (body)))
        !           351:        return 1;
        !           352:       break;
        !           353: 
        !           354:     case ASM_OPERANDS:
        !           355:       for (i = ASM_OPERANDS_INPUT_LENGTH (body) - 1; i >= 0; i--)
        !           356:        if (reg_overlap_mentioned_p (x, ASM_OPERANDS_INPUT (body, i)))
        !           357:          return 1;
        !           358:       break;
        !           359: 
        !           360:     case CALL:
        !           361:     case USE:
        !           362:       return reg_overlap_mentioned_p (x, body);
        !           363: 
        !           364:     case TRAP_IF:
        !           365:       return reg_overlap_mentioned_p (x, TRAP_CONDITION (body));
        !           366: 
        !           367:     case UNSPEC:
        !           368:     case UNSPEC_VOLATILE:
        !           369:     case PARALLEL:
        !           370:       for (i = XVECLEN (body, 0) - 1; i >= 0; i--)
        !           371:        if (reg_referenced_p (x, XVECEXP (body, 0, i)))
        !           372:          return 1;
        !           373:       break;
        !           374:     }
        !           375: 
        !           376:   return 0;
        !           377: }
        !           378: 
        !           379: /* Nonzero if register REG is referenced in an insn between
        !           380:    FROM_INSN and TO_INSN (exclusive of those two).  Sets of REG do
        !           381:    not count. */
        !           382: 
        !           383: int
        !           384: reg_referenced_between_p (reg, from_insn, to_insn)
        !           385:      rtx reg, from_insn, to_insn;
        !           386: {
        !           387:   register rtx insn;
        !           388: 
        !           389:   if (from_insn == to_insn)
        !           390:     return 0;
        !           391: 
        !           392:   for (insn = NEXT_INSN (from_insn); insn != to_insn; insn = NEXT_INSN (insn))
        !           393:     if (GET_RTX_CLASS (GET_CODE (insn)) == 'i'
        !           394:        && reg_referenced_p (reg, PATTERN (insn)))
        !           395:       return 1;
        !           396:   return 0;
        !           397: }
        !           398: 
        !           399: /* Nonzero if register REG is set or clobbered in an insn between
        !           400:    FROM_INSN and TO_INSN (exclusive of those two).  */
        !           401: 
        !           402: int
        !           403: reg_set_between_p (reg, from_insn, to_insn)
        !           404:      rtx reg, from_insn, to_insn;
        !           405: {
        !           406:   register rtx insn;
        !           407: 
        !           408:   if (from_insn == to_insn)
        !           409:     return 0;
        !           410: 
        !           411:   for (insn = NEXT_INSN (from_insn); insn != to_insn; insn = NEXT_INSN (insn))
        !           412:     if (GET_RTX_CLASS (GET_CODE (insn)) == 'i'
        !           413:        && reg_set_p (reg, insn))
        !           414:       return 1;
        !           415:   return 0;
        !           416: }
        !           417: 
        !           418: /* Internals of reg_set_between_p.  */
        !           419: 
        !           420: static rtx reg_set_reg;
        !           421: static int reg_set_flag;
        !           422: 
        !           423: void
        !           424: reg_set_p_1 (x)
        !           425:      rtx x;
        !           426: {
        !           427:   /* We don't want to return 1 if X is a MEM that contains a register
        !           428:      within REG_SET_REG.  */
        !           429: 
        !           430:   if ((GET_CODE (x) != MEM)
        !           431:       && reg_overlap_mentioned_p (reg_set_reg, x))
        !           432:     reg_set_flag = 1;
        !           433: }
        !           434: 
        !           435: int
        !           436: reg_set_p (reg, insn)
        !           437:      rtx reg, insn;
        !           438: {
        !           439:   rtx body = insn;
        !           440: 
        !           441:   /* We can be passed an insn or part of one.  If we are passed an insn,
        !           442:      check if a side-effect of the insn clobbers REG.  */
        !           443:   if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
        !           444:     {
        !           445:       if (FIND_REG_INC_NOTE (insn, reg)
        !           446:          || (GET_CODE (insn) == CALL_INSN
        !           447:              /* We'd like to test call_used_regs here, but rtlanal.c can't
        !           448:                 reference that variable due to its use in genattrtab.  So
        !           449:                 we'll just be more conservative.  */
        !           450:              && ((GET_CODE (reg) == REG
        !           451:                   && REGNO (reg) < FIRST_PSEUDO_REGISTER)
        !           452:                  || GET_CODE (reg) == MEM)))
        !           453:        return 1;
        !           454: 
        !           455:       body = PATTERN (insn);
        !           456:     }
        !           457: 
        !           458:   reg_set_reg = reg;
        !           459:   reg_set_flag = 0;
        !           460:   note_stores (body, reg_set_p_1);
        !           461:   return reg_set_flag;
        !           462: }
        !           463: 
        !           464: /* Similar to reg_set_between_p, but check all registers in X.  Return 0
        !           465:    only if none of them are modified between START and END.  Return 1 if
        !           466:    X contains a MEM; this routine does not perform any memory aliasing.  */
        !           467: 
        !           468: int
        !           469: modified_between_p (x, start, end)
        !           470:      rtx x;
        !           471:      rtx start, end;
        !           472: {
        !           473:   enum rtx_code code = GET_CODE (x);
        !           474:   char *fmt;
        !           475:   int i;
        !           476: 
        !           477:   switch (code)
        !           478:     {
        !           479:     case CONST_INT:
        !           480:     case CONST_DOUBLE:
        !           481:     case CONST:
        !           482:     case SYMBOL_REF:
        !           483:     case LABEL_REF:
        !           484:       return 0;
        !           485: 
        !           486:     case PC:
        !           487:     case CC0:
        !           488:       return 1;
        !           489: 
        !           490:     case MEM:
        !           491:       /* If the memory is not constant, assume it is modified.  If it is
        !           492:         constant, we still have to check the address.  */
        !           493:       if (! RTX_UNCHANGING_P (x))
        !           494:        return 1;
        !           495:       break;
        !           496: 
        !           497:     case REG:
        !           498:       return reg_set_between_p (x, start, end);
        !           499:     }
        !           500: 
        !           501:   fmt = GET_RTX_FORMAT (code);
        !           502:   for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
        !           503:     if (fmt[i] == 'e'
        !           504:        && modified_between_p (XEXP (x, i), start, end))
        !           505:       return 1;
        !           506: 
        !           507:   return 0;
        !           508: }
        !           509: 
        !           510: /* Given an INSN, return a SET expression if this insn has only a single SET.
        !           511:    It may also have CLOBBERs, USEs, or SET whose output
        !           512:    will not be used, which we ignore.  */
        !           513: 
        !           514: rtx
        !           515: single_set (insn)
        !           516:      rtx insn;
        !           517: {
        !           518:   rtx set;
        !           519:   int i;
        !           520:   
        !           521:   if (GET_RTX_CLASS (GET_CODE (insn)) != 'i')
        !           522:     return 0;
        !           523: 
        !           524:   if (GET_CODE (PATTERN (insn)) == SET)
        !           525:     return PATTERN (insn);
        !           526:   
        !           527:   else if (GET_CODE (PATTERN (insn)) == PARALLEL)
        !           528:     {
        !           529:       for (i = 0, set = 0; i < XVECLEN (PATTERN (insn), 0); i++)
        !           530:        if (GET_CODE (XVECEXP (PATTERN (insn), 0, i)) == SET
        !           531:            && ! (find_reg_note (insn, REG_UNUSED,
        !           532:                                SET_DEST (XVECEXP (PATTERN (insn), 0, i)))
        !           533:                  || side_effects_p (XVECEXP (PATTERN (insn), 0, i))))
        !           534:          {
        !           535:            if (set)
        !           536:              return 0;
        !           537:            else
        !           538:              set = XVECEXP (PATTERN (insn), 0, i);
        !           539:          }
        !           540:       return set;
        !           541:     }
        !           542:   
        !           543:   return 0;
        !           544: }
        !           545: 
        !           546: /* Return the last thing that X was assigned from before *PINSN.  Verify that
        !           547:    the object is not modified up to VALID_TO.  If it was, if we hit
        !           548:    a partial assignment to X, or hit a CODE_LABEL first, return X.  If we
        !           549:    found an assignment, update *PINSN to point to it.  */
        !           550: 
        !           551: rtx
        !           552: find_last_value (x, pinsn, valid_to)
        !           553:      rtx x;
        !           554:      rtx *pinsn;
        !           555:      rtx valid_to;
        !           556: {
        !           557:   rtx p;
        !           558: 
        !           559:   for (p = PREV_INSN (*pinsn); p && GET_CODE (p) != CODE_LABEL;
        !           560:        p = PREV_INSN (p))
        !           561:     if (GET_RTX_CLASS (GET_CODE (p)) == 'i')
        !           562:       {
        !           563:        rtx set = single_set (p);
        !           564:        rtx note = find_reg_note (p, REG_EQUAL, 0);
        !           565: 
        !           566:        if (set && rtx_equal_p (x, SET_DEST (set)))
        !           567:          {
        !           568:            rtx src = SET_SRC (set);
        !           569: 
        !           570:            if (note && GET_CODE (XEXP (note, 0)) != EXPR_LIST)
        !           571:              src = XEXP (note, 0);
        !           572: 
        !           573:            if (! modified_between_p (src, PREV_INSN (p), valid_to)
        !           574:                /* Reject hard registers because we don't usually want
        !           575:                   to use them; we'd rather use a pseudo.  */
        !           576:                && ! (GET_CODE (src) == REG
        !           577:                      && REGNO (src) < FIRST_PSEUDO_REGISTER))
        !           578:              {
        !           579:                *pinsn = p;
        !           580:                return src;
        !           581:              }
        !           582:          }
        !           583:          
        !           584:        /* If set in non-simple way, we don't have a value.  */
        !           585:        if (reg_set_p (x, p))
        !           586:          break;
        !           587:       }
        !           588: 
        !           589:   return x;
        !           590: }     
        !           591: 
        !           592: /* Return nonzero if register in range [REGNO, ENDREGNO)
        !           593:    appears either explicitly or implicitly in X
        !           594:    other than being stored into.
        !           595: 
        !           596:    References contained within the substructure at LOC do not count.
        !           597:    LOC may be zero, meaning don't ignore anything.  */
        !           598: 
        !           599: int
        !           600: refers_to_regno_p (regno, endregno, x, loc)
        !           601:      int regno, endregno;
        !           602:      rtx x;
        !           603:      rtx *loc;
        !           604: {
        !           605:   register int i;
        !           606:   register RTX_CODE code;
        !           607:   register char *fmt;
        !           608: 
        !           609:  repeat:
        !           610:   /* The contents of a REG_NONNEG note is always zero, so we must come here
        !           611:      upon repeat in case the last REG_NOTE is a REG_NONNEG note.  */
        !           612:   if (x == 0)
        !           613:     return 0;
        !           614: 
        !           615:   code = GET_CODE (x);
        !           616: 
        !           617:   switch (code)
        !           618:     {
        !           619:     case REG:
        !           620:       i = REGNO (x);
        !           621:       return (endregno > i
        !           622:              && regno < i + (i < FIRST_PSEUDO_REGISTER 
        !           623:                              ? HARD_REGNO_NREGS (i, GET_MODE (x))
        !           624:                              : 1));
        !           625: 
        !           626:     case SUBREG:
        !           627:       /* If this is a SUBREG of a hard reg, we can see exactly which
        !           628:         registers are being modified.  Otherwise, handle normally.  */
        !           629:       if (GET_CODE (SUBREG_REG (x)) == REG
        !           630:          && REGNO (SUBREG_REG (x)) < FIRST_PSEUDO_REGISTER)
        !           631:        {
        !           632:          int inner_regno = REGNO (SUBREG_REG (x)) + SUBREG_WORD (x);
        !           633:          int inner_endregno
        !           634:            = inner_regno + (inner_regno < FIRST_PSEUDO_REGISTER
        !           635:                             ? HARD_REGNO_NREGS (regno, GET_MODE (x)) : 1);
        !           636: 
        !           637:          return endregno > inner_regno && regno < inner_endregno;
        !           638:        }
        !           639:       break;
        !           640: 
        !           641:     case CLOBBER:
        !           642:     case SET:
        !           643:       if (&SET_DEST (x) != loc
        !           644:          /* Note setting a SUBREG counts as referring to the REG it is in for
        !           645:             a pseudo but not for hard registers since we can
        !           646:             treat each word individually.  */
        !           647:          && ((GET_CODE (SET_DEST (x)) == SUBREG
        !           648:               && loc != &SUBREG_REG (SET_DEST (x))
        !           649:               && GET_CODE (SUBREG_REG (SET_DEST (x))) == REG
        !           650:               && REGNO (SUBREG_REG (SET_DEST (x))) >= FIRST_PSEUDO_REGISTER
        !           651:               && refers_to_regno_p (regno, endregno,
        !           652:                                     SUBREG_REG (SET_DEST (x)), loc))
        !           653:              || (GET_CODE (SET_DEST (x)) != REG
        !           654:                  && refers_to_regno_p (regno, endregno, SET_DEST (x), loc))))
        !           655:        return 1;
        !           656: 
        !           657:       if (code == CLOBBER || loc == &SET_SRC (x))
        !           658:        return 0;
        !           659:       x = SET_SRC (x);
        !           660:       goto repeat;
        !           661:     }
        !           662: 
        !           663:   /* X does not match, so try its subexpressions.  */
        !           664: 
        !           665:   fmt = GET_RTX_FORMAT (code);
        !           666:   for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
        !           667:     {
        !           668:       if (fmt[i] == 'e' && loc != &XEXP (x, i))
        !           669:        {
        !           670:          if (i == 0)
        !           671:            {
        !           672:              x = XEXP (x, 0);
        !           673:              goto repeat;
        !           674:            }
        !           675:          else
        !           676:            if (refers_to_regno_p (regno, endregno, XEXP (x, i), loc))
        !           677:              return 1;
        !           678:        }
        !           679:       else if (fmt[i] == 'E')
        !           680:        {
        !           681:          register int j;
        !           682:          for (j = XVECLEN (x, i) - 1; j >=0; j--)
        !           683:            if (loc != &XVECEXP (x, i, j)
        !           684:                && refers_to_regno_p (regno, endregno, XVECEXP (x, i, j), loc))
        !           685:              return 1;
        !           686:        }
        !           687:     }
        !           688:   return 0;
        !           689: }
        !           690: 
        !           691: /* Nonzero if modifying X will affect IN.  If X is a register or a SUBREG,
        !           692:    we check if any register number in X conflicts with the relevant register
        !           693:    numbers.  If X is a constant, return 0.  If X is a MEM, return 1 iff IN
        !           694:    contains a MEM (we don't bother checking for memory addresses that can't
        !           695:    conflict because we expect this to be a rare case.  */
        !           696: 
        !           697: int
        !           698: reg_overlap_mentioned_p (x, in)
        !           699:      rtx x, in;
        !           700: {
        !           701:   int regno, endregno;
        !           702: 
        !           703:   if (GET_CODE (x) == SUBREG)
        !           704:     {
        !           705:       regno = REGNO (SUBREG_REG (x));
        !           706:       if (regno < FIRST_PSEUDO_REGISTER)
        !           707:        regno += SUBREG_WORD (x);
        !           708:     }
        !           709:   else if (GET_CODE (x) == REG)
        !           710:     regno = REGNO (x);
        !           711:   else if (CONSTANT_P (x))
        !           712:     return 0;
        !           713:   else if (GET_CODE (x) == MEM)
        !           714:     {
        !           715:       char *fmt;
        !           716:       int i;
        !           717: 
        !           718:       if (GET_CODE (in) == MEM)
        !           719:        return 1;
        !           720: 
        !           721:       fmt = GET_RTX_FORMAT (GET_CODE (in));
        !           722: 
        !           723:       for (i = GET_RTX_LENGTH (GET_CODE (in)) - 1; i >= 0; i--)
        !           724:        if (fmt[i] == 'e' && reg_overlap_mentioned_p (x, XEXP (in, i)))
        !           725:          return 1;
        !           726: 
        !           727:       return 0;
        !           728:     }
        !           729:   else if (GET_CODE (x) == SCRATCH || GET_CODE (x) == PC
        !           730:           || GET_CODE (x) == CC0)
        !           731:     return reg_mentioned_p (x, in);
        !           732:   else
        !           733:     abort ();
        !           734: 
        !           735:   endregno = regno + (regno < FIRST_PSEUDO_REGISTER
        !           736:                      ? HARD_REGNO_NREGS (regno, GET_MODE (x)) : 1);
        !           737: 
        !           738:   return refers_to_regno_p (regno, endregno, in, 0);
        !           739: }
        !           740: 
        !           741: /* Used for communications between the next few functions.  */
        !           742: 
        !           743: static int reg_set_last_unknown;
        !           744: static rtx reg_set_last_value;
        !           745: static int reg_set_last_first_regno, reg_set_last_last_regno;
        !           746: 
        !           747: /* Called via note_stores from reg_set_last.  */
        !           748: 
        !           749: static void
        !           750: reg_set_last_1 (x, pat)
        !           751:      rtx x;
        !           752:      rtx pat;
        !           753: {
        !           754:   int first, last;
        !           755: 
        !           756:   /* If X is not a register, or is not one in the range we care
        !           757:      about, ignore.  */
        !           758:   if (GET_CODE (x) != REG)
        !           759:     return;
        !           760: 
        !           761:   first = REGNO (x);
        !           762:   last = first + (first < FIRST_PSEUDO_REGISTER
        !           763:                  ? HARD_REGNO_NREGS (first, GET_MODE (x)) : 1);
        !           764: 
        !           765:   if (first >= reg_set_last_last_regno
        !           766:       || last <= reg_set_last_first_regno)
        !           767:     return;
        !           768: 
        !           769:   /* If this is a CLOBBER or is some complex LHS, or doesn't modify
        !           770:      exactly the registers we care about, show we don't know the value.  */
        !           771:   if (GET_CODE (pat) == CLOBBER || SET_DEST (pat) != x
        !           772:       || first != reg_set_last_first_regno
        !           773:       || last != reg_set_last_last_regno)
        !           774:     reg_set_last_unknown = 1;
        !           775:   else
        !           776:     reg_set_last_value = SET_SRC (pat);
        !           777: }
        !           778: 
        !           779: /* Return the last value to which REG was set prior to INSN.  If we can't
        !           780:    find it easily, return 0.
        !           781: 
        !           782:    We only return a REG or constant because it is too hard to check if a
        !           783:    MEM remains unchanged.  */
        !           784: 
        !           785: rtx
        !           786: reg_set_last (x, insn)
        !           787:      rtx x;
        !           788:      rtx insn;
        !           789: {
        !           790:   rtx orig_insn = insn;
        !           791: 
        !           792:   reg_set_last_first_regno = REGNO (x);
        !           793: 
        !           794:   reg_set_last_last_regno
        !           795:     = reg_set_last_first_regno
        !           796:       + (reg_set_last_first_regno < FIRST_PSEUDO_REGISTER
        !           797:         ? HARD_REGNO_NREGS (reg_set_last_first_regno, GET_MODE (x)) : 1);
        !           798: 
        !           799:   reg_set_last_unknown = 0;
        !           800:   reg_set_last_value = 0;
        !           801: 
        !           802:   /* Scan backwards until reg_set_last_1 changed one of the above flags.
        !           803:      Stop when we reach a label or X is a hard reg and we reach a
        !           804:      CALL_INSN (if reg_set_last_last_regno is a hard reg).
        !           805: 
        !           806:      If we find a set of X, ensure that its SET_SRC remains unchanged.  */
        !           807: 
        !           808:   for (;
        !           809:        insn && GET_CODE (insn) != CODE_LABEL
        !           810:        && ! (GET_CODE (insn) == CALL_INSN
        !           811:             && reg_set_last_last_regno <= FIRST_PSEUDO_REGISTER);
        !           812:        insn = PREV_INSN (insn))
        !           813:     if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
        !           814:       {
        !           815:        note_stores (PATTERN (insn), reg_set_last_1);
        !           816:        if (reg_set_last_unknown)
        !           817:          return 0;
        !           818:        else if (reg_set_last_value)
        !           819:          {
        !           820:            if (CONSTANT_P (reg_set_last_value)
        !           821:                || (GET_CODE (reg_set_last_value) == REG
        !           822:                    && ! reg_set_between_p (reg_set_last_value,
        !           823:                                            NEXT_INSN (insn), orig_insn)))
        !           824:              return reg_set_last_value;
        !           825:            else
        !           826:              return 0;
        !           827:          }
        !           828:       }
        !           829: 
        !           830:   return 0;
        !           831: }
        !           832: 
        !           833: /* This is 1 until after reload pass.  */
        !           834: int rtx_equal_function_value_matters;
        !           835: 
        !           836: /* Return 1 if X and Y are identical-looking rtx's.
        !           837:    This is the Lisp function EQUAL for rtx arguments.  */
        !           838: 
        !           839: int
        !           840: rtx_equal_p (x, y)
        !           841:      rtx x, y;
        !           842: {
        !           843:   register int i;
        !           844:   register int j;
        !           845:   register enum rtx_code code;
        !           846:   register char *fmt;
        !           847: 
        !           848:   if (x == y)
        !           849:     return 1;
        !           850:   if (x == 0 || y == 0)
        !           851:     return 0;
        !           852: 
        !           853:   code = GET_CODE (x);
        !           854:   /* Rtx's of different codes cannot be equal.  */
        !           855:   if (code != GET_CODE (y))
        !           856:     return 0;
        !           857: 
        !           858:   /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
        !           859:      (REG:SI x) and (REG:HI x) are NOT equivalent.  */
        !           860: 
        !           861:   if (GET_MODE (x) != GET_MODE (y))
        !           862:     return 0;
        !           863: 
        !           864:   /* REG, LABEL_REF, and SYMBOL_REF can be compared nonrecursively.  */
        !           865: 
        !           866:   if (code == REG)
        !           867:     /* Until rtl generation is complete, don't consider a reference to the
        !           868:        return register of the current function the same as the return from a
        !           869:        called function.  This eases the job of function integration.  Once the
        !           870:        distinction is no longer needed, they can be considered equivalent.  */
        !           871:     return (REGNO (x) == REGNO (y)
        !           872:            && (! rtx_equal_function_value_matters
        !           873:                || REG_FUNCTION_VALUE_P (x) == REG_FUNCTION_VALUE_P (y)));
        !           874:   else if (code == LABEL_REF)
        !           875:     return XEXP (x, 0) == XEXP (y, 0);
        !           876:   else if (code == SYMBOL_REF)
        !           877:     return XSTR (x, 0) == XSTR (y, 0);
        !           878:   else if (code == SCRATCH || code == CONST_DOUBLE)
        !           879:     return 0;
        !           880: 
        !           881:   /* Compare the elements.  If any pair of corresponding elements
        !           882:      fail to match, return 0 for the whole things.  */
        !           883: 
        !           884:   fmt = GET_RTX_FORMAT (code);
        !           885:   for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
        !           886:     {
        !           887:       switch (fmt[i])
        !           888:        {
        !           889:        case 'n':
        !           890:        case 'i':
        !           891:          if (XINT (x, i) != XINT (y, i))
        !           892:            return 0;
        !           893:          break;
        !           894: 
        !           895:        case 'V':
        !           896:        case 'E':
        !           897:          /* Two vectors must have the same length.  */
        !           898:          if (XVECLEN (x, i) != XVECLEN (y, i))
        !           899:            return 0;
        !           900: 
        !           901:          /* And the corresponding elements must match.  */
        !           902:          for (j = 0; j < XVECLEN (x, i); j++)
        !           903:            if (rtx_equal_p (XVECEXP (x, i, j), XVECEXP (y, i, j)) == 0)
        !           904:              return 0;
        !           905:          break;
        !           906: 
        !           907:        case 'e':
        !           908:          if (rtx_equal_p (XEXP (x, i), XEXP (y, i)) == 0)
        !           909:            return 0;
        !           910:          break;
        !           911: 
        !           912:        case 'S':
        !           913:        case 's':
        !           914:          if (strcmp (XSTR (x, i), XSTR (y, i)))
        !           915:            return 0;
        !           916:          break;
        !           917: 
        !           918:        case 'u':
        !           919:          /* These are just backpointers, so they don't matter.  */
        !           920:          break;
        !           921: 
        !           922:        case '0':
        !           923:          break;
        !           924: 
        !           925:          /* It is believed that rtx's at this level will never
        !           926:             contain anything but integers and other rtx's,
        !           927:             except for within LABEL_REFs and SYMBOL_REFs.  */
        !           928:        default:
        !           929:          abort ();
        !           930:        }
        !           931:     }
        !           932:   return 1;
        !           933: }
        !           934: 
        !           935: /* Call FUN on each register or MEM that is stored into or clobbered by X.
        !           936:    (X would be the pattern of an insn).
        !           937:    FUN receives two arguments:
        !           938:      the REG, MEM, CC0 or PC being stored in or clobbered,
        !           939:      the SET or CLOBBER rtx that does the store.
        !           940: 
        !           941:   If the item being stored in or clobbered is a SUBREG of a hard register,
        !           942:   the SUBREG will be passed.  */
        !           943:      
        !           944: void
        !           945: note_stores (x, fun)
        !           946:      register rtx x;
        !           947:      void (*fun) ();
        !           948: {
        !           949:   if ((GET_CODE (x) == SET || GET_CODE (x) == CLOBBER))
        !           950:     {
        !           951:       register rtx dest = SET_DEST (x);
        !           952:       while ((GET_CODE (dest) == SUBREG
        !           953:              && (GET_CODE (SUBREG_REG (dest)) != REG
        !           954:                  || REGNO (SUBREG_REG (dest)) >= FIRST_PSEUDO_REGISTER))
        !           955:             || GET_CODE (dest) == ZERO_EXTRACT
        !           956:             || GET_CODE (dest) == SIGN_EXTRACT
        !           957:             || GET_CODE (dest) == STRICT_LOW_PART)
        !           958:        dest = XEXP (dest, 0);
        !           959:       (*fun) (dest, x);
        !           960:     }
        !           961:   else if (GET_CODE (x) == PARALLEL)
        !           962:     {
        !           963:       register int i;
        !           964:       for (i = XVECLEN (x, 0) - 1; i >= 0; i--)
        !           965:        {
        !           966:          register rtx y = XVECEXP (x, 0, i);
        !           967:          if (GET_CODE (y) == SET || GET_CODE (y) == CLOBBER)
        !           968:            {
        !           969:              register rtx dest = SET_DEST (y);
        !           970:              while ((GET_CODE (dest) == SUBREG
        !           971:                      && (GET_CODE (SUBREG_REG (dest)) != REG
        !           972:                          || (REGNO (SUBREG_REG (dest))
        !           973:                              >= FIRST_PSEUDO_REGISTER)))
        !           974:                     || GET_CODE (dest) == ZERO_EXTRACT
        !           975:                     || GET_CODE (dest) == SIGN_EXTRACT
        !           976:                     || GET_CODE (dest) == STRICT_LOW_PART)
        !           977:                dest = XEXP (dest, 0);
        !           978:              (*fun) (dest, y);
        !           979:            }
        !           980:        }
        !           981:     }
        !           982: }
        !           983: 
        !           984: /* Return nonzero if X's old contents don't survive after INSN.
        !           985:    This will be true if X is (cc0) or if X is a register and
        !           986:    X dies in INSN or because INSN entirely sets X.
        !           987: 
        !           988:    "Entirely set" means set directly and not through a SUBREG,
        !           989:    ZERO_EXTRACT or SIGN_EXTRACT, so no trace of the old contents remains.
        !           990:    Likewise, REG_INC does not count.
        !           991: 
        !           992:    REG may be a hard or pseudo reg.  Renumbering is not taken into account,
        !           993:    but for this use that makes no difference, since regs don't overlap
        !           994:    during their lifetimes.  Therefore, this function may be used
        !           995:    at any time after deaths have been computed (in flow.c).
        !           996: 
        !           997:    If REG is a hard reg that occupies multiple machine registers, this
        !           998:    function will only return 1 if each of those registers will be replaced
        !           999:    by INSN.  */
        !          1000: 
        !          1001: int
        !          1002: dead_or_set_p (insn, x)
        !          1003:      rtx insn;
        !          1004:      rtx x;
        !          1005: {
        !          1006:   register int regno, last_regno;
        !          1007:   register int i;
        !          1008: 
        !          1009:   /* Can't use cc0_rtx below since this file is used by genattrtab.c.  */
        !          1010:   if (GET_CODE (x) == CC0)
        !          1011:     return 1;
        !          1012: 
        !          1013:   if (GET_CODE (x) != REG)
        !          1014:     abort ();
        !          1015: 
        !          1016:   regno = REGNO (x);
        !          1017:   last_regno = (regno >= FIRST_PSEUDO_REGISTER ? regno
        !          1018:                : regno + HARD_REGNO_NREGS (regno, GET_MODE (x)) - 1);
        !          1019: 
        !          1020:   for (i = regno; i <= last_regno; i++)
        !          1021:     if (! dead_or_set_regno_p (insn, i))
        !          1022:       return 0;
        !          1023: 
        !          1024:   return 1;
        !          1025: }
        !          1026: 
        !          1027: /* Utility function for dead_or_set_p to check an individual register.  Also
        !          1028:    called from flow.c.  */
        !          1029: 
        !          1030: int
        !          1031: dead_or_set_regno_p (insn, test_regno)
        !          1032:      rtx insn;
        !          1033:      int test_regno;
        !          1034: {
        !          1035:   int regno, endregno;
        !          1036:   rtx link;
        !          1037: 
        !          1038:   /* See if there is a death note for something that includes TEST_REGNO.  */
        !          1039:   for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
        !          1040:     {
        !          1041:       if (REG_NOTE_KIND (link) != REG_DEAD || GET_CODE (XEXP (link, 0)) != REG)
        !          1042:        continue;
        !          1043: 
        !          1044:       regno = REGNO (XEXP (link, 0));
        !          1045:       endregno = (regno >= FIRST_PSEUDO_REGISTER ? regno + 1
        !          1046:                  : regno + HARD_REGNO_NREGS (regno,
        !          1047:                                              GET_MODE (XEXP (link, 0))));
        !          1048: 
        !          1049:       if (test_regno >= regno && test_regno < endregno)
        !          1050:        return 1;
        !          1051:     }
        !          1052: 
        !          1053:   if (GET_CODE (PATTERN (insn)) == SET)
        !          1054:     {
        !          1055:       rtx dest = SET_DEST (PATTERN (insn));
        !          1056:  
        !          1057:       /* A value is totally replaced if it is the destination or the
        !          1058:         destination is a SUBREG of REGNO that does not change the number of
        !          1059:         words in it.  */
        !          1060:      if (GET_CODE (dest) == SUBREG
        !          1061:          && (((GET_MODE_SIZE (GET_MODE (dest))
        !          1062:                + UNITS_PER_WORD - 1) / UNITS_PER_WORD)
        !          1063:              == ((GET_MODE_SIZE (GET_MODE (SUBREG_REG (dest)))
        !          1064:                   + UNITS_PER_WORD - 1) / UNITS_PER_WORD)))
        !          1065:        dest = SUBREG_REG (dest);
        !          1066: 
        !          1067:       if (GET_CODE (dest) != REG)
        !          1068:        return 0;
        !          1069: 
        !          1070:       regno = REGNO (dest);
        !          1071:       endregno = (regno >= FIRST_PSEUDO_REGISTER ? regno + 1
        !          1072:                  : regno + HARD_REGNO_NREGS (regno, GET_MODE (dest)));
        !          1073: 
        !          1074:       return (test_regno >= regno && test_regno < endregno);
        !          1075:     }
        !          1076:   else if (GET_CODE (PATTERN (insn)) == PARALLEL)
        !          1077:     {
        !          1078:       register int i;
        !          1079: 
        !          1080:       for (i = XVECLEN (PATTERN (insn), 0) - 1; i >= 0; i--)
        !          1081:        {
        !          1082:          rtx body = XVECEXP (PATTERN (insn), 0, i);
        !          1083: 
        !          1084:          if (GET_CODE (body) == SET || GET_CODE (body) == CLOBBER)
        !          1085:            {
        !          1086:              rtx dest = SET_DEST (body);
        !          1087: 
        !          1088:              if (GET_CODE (dest) == SUBREG
        !          1089:                  && (((GET_MODE_SIZE (GET_MODE (dest))
        !          1090:                        + UNITS_PER_WORD - 1) / UNITS_PER_WORD)
        !          1091:                      == ((GET_MODE_SIZE (GET_MODE (SUBREG_REG (dest)))
        !          1092:                           + UNITS_PER_WORD - 1) / UNITS_PER_WORD)))
        !          1093:                dest = SUBREG_REG (dest);
        !          1094: 
        !          1095:              if (GET_CODE (dest) != REG)
        !          1096:                continue;
        !          1097: 
        !          1098:              regno = REGNO (dest);
        !          1099:              endregno = (regno >= FIRST_PSEUDO_REGISTER ? regno + 1
        !          1100:                          : regno + HARD_REGNO_NREGS (regno, GET_MODE (dest)));
        !          1101: 
        !          1102:              if (test_regno >= regno && test_regno < endregno)
        !          1103:                return 1;
        !          1104:            }
        !          1105:        }
        !          1106:     }
        !          1107: 
        !          1108:   return 0;
        !          1109: }
        !          1110: 
        !          1111: /* Return the reg-note of kind KIND in insn INSN, if there is one.
        !          1112:    If DATUM is nonzero, look for one whose datum is DATUM.  */
        !          1113: 
        !          1114: rtx
        !          1115: find_reg_note (insn, kind, datum)
        !          1116:      rtx insn;
        !          1117:      enum reg_note kind;
        !          1118:      rtx datum;
        !          1119: {
        !          1120:   register rtx link;
        !          1121: 
        !          1122:   for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
        !          1123:     if (REG_NOTE_KIND (link) == kind
        !          1124:        && (datum == 0 || datum == XEXP (link, 0)))
        !          1125:       return link;
        !          1126:   return 0;
        !          1127: }
        !          1128: 
        !          1129: /* Return the reg-note of kind KIND in insn INSN which applies to register
        !          1130:    number REGNO, if any.  Return 0 if there is no such reg-note.  */
        !          1131: 
        !          1132: rtx
        !          1133: find_regno_note (insn, kind, regno)
        !          1134:      rtx insn;
        !          1135:      enum reg_note kind;
        !          1136:      int regno;
        !          1137: {
        !          1138:   register rtx link;
        !          1139: 
        !          1140:   for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
        !          1141:     if (REG_NOTE_KIND (link) == kind
        !          1142:        /* Verify that it is a register, so that scratch and MEM won't cause a
        !          1143:           problem here.  */
        !          1144:        && GET_CODE (XEXP (link, 0)) == REG
        !          1145:        && REGNO (XEXP (link, 0)) == regno)
        !          1146:       return link;
        !          1147:   return 0;
        !          1148: }
        !          1149: 
        !          1150: /* Remove register note NOTE from the REG_NOTES of INSN.  */
        !          1151: 
        !          1152: void
        !          1153: remove_note (insn, note)
        !          1154:      register rtx note;
        !          1155:      register rtx insn;
        !          1156: {
        !          1157:   register rtx link;
        !          1158: 
        !          1159:   if (REG_NOTES (insn) == note)
        !          1160:     {
        !          1161:       REG_NOTES (insn) = XEXP (note, 1);
        !          1162:       return;
        !          1163:     }
        !          1164: 
        !          1165:   for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
        !          1166:     if (XEXP (link, 1) == note)
        !          1167:       {
        !          1168:        XEXP (link, 1) = XEXP (note, 1);
        !          1169:        return;
        !          1170:       }
        !          1171: 
        !          1172:   abort ();
        !          1173: }
        !          1174: 
        !          1175: /* Nonzero if X contains any volatile memory references
        !          1176:    UNSPEC_VOLATILE operations or volatile ASM_OPERANDS expressions.  */
        !          1177: 
        !          1178: int
        !          1179: volatile_refs_p (x)
        !          1180:      rtx x;
        !          1181: {
        !          1182:   register RTX_CODE code;
        !          1183: 
        !          1184:   code = GET_CODE (x);
        !          1185:   switch (code)
        !          1186:     {
        !          1187:     case LABEL_REF:
        !          1188:     case SYMBOL_REF:
        !          1189:     case CONST_INT:
        !          1190:     case CONST:
        !          1191:     case CONST_DOUBLE:
        !          1192:     case CC0:
        !          1193:     case PC:
        !          1194:     case REG:
        !          1195:     case SCRATCH:
        !          1196:     case CLOBBER:
        !          1197:     case ASM_INPUT:
        !          1198:     case ADDR_VEC:
        !          1199:     case ADDR_DIFF_VEC:
        !          1200:       return 0;
        !          1201: 
        !          1202:     case CALL:
        !          1203:     case UNSPEC_VOLATILE:
        !          1204:  /* case TRAP_IF: This isn't clear yet.  */
        !          1205:       return 1;
        !          1206: 
        !          1207:     case MEM:
        !          1208:     case ASM_OPERANDS:
        !          1209:       if (MEM_VOLATILE_P (x))
        !          1210:        return 1;
        !          1211:     }
        !          1212: 
        !          1213:   /* Recursively scan the operands of this expression.  */
        !          1214: 
        !          1215:   {
        !          1216:     register char *fmt = GET_RTX_FORMAT (code);
        !          1217:     register int i;
        !          1218:     
        !          1219:     for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
        !          1220:       {
        !          1221:        if (fmt[i] == 'e')
        !          1222:          {
        !          1223:            if (volatile_refs_p (XEXP (x, i)))
        !          1224:              return 1;
        !          1225:          }
        !          1226:        if (fmt[i] == 'E')
        !          1227:          {
        !          1228:            register int j;
        !          1229:            for (j = 0; j < XVECLEN (x, i); j++)
        !          1230:              if (volatile_refs_p (XVECEXP (x, i, j)))
        !          1231:                return 1;
        !          1232:          }
        !          1233:       }
        !          1234:   }
        !          1235:   return 0;
        !          1236: }
        !          1237: 
        !          1238: /* Similar to above, except that it also rejects register pre- and post-
        !          1239:    incrementing.  */
        !          1240: 
        !          1241: int
        !          1242: side_effects_p (x)
        !          1243:      rtx x;
        !          1244: {
        !          1245:   register RTX_CODE code;
        !          1246: 
        !          1247:   code = GET_CODE (x);
        !          1248:   switch (code)
        !          1249:     {
        !          1250:     case LABEL_REF:
        !          1251:     case SYMBOL_REF:
        !          1252:     case CONST_INT:
        !          1253:     case CONST:
        !          1254:     case CONST_DOUBLE:
        !          1255:     case CC0:
        !          1256:     case PC:
        !          1257:     case REG:
        !          1258:     case SCRATCH:
        !          1259:     case ASM_INPUT:
        !          1260:     case ADDR_VEC:
        !          1261:     case ADDR_DIFF_VEC:
        !          1262:       return 0;
        !          1263: 
        !          1264:     case CLOBBER:
        !          1265:       /* Reject CLOBBER with a non-VOID mode.  These are made by combine.c
        !          1266:         when some combination can't be done.  If we see one, don't think
        !          1267:         that we can simplify the expression.  */
        !          1268:       return (GET_MODE (x) != VOIDmode);
        !          1269: 
        !          1270:     case PRE_INC:
        !          1271:     case PRE_DEC:
        !          1272:     case POST_INC:
        !          1273:     case POST_DEC:
        !          1274:     case CALL:
        !          1275:     case UNSPEC_VOLATILE:
        !          1276:  /* case TRAP_IF: This isn't clear yet.  */
        !          1277:       return 1;
        !          1278: 
        !          1279:     case MEM:
        !          1280:     case ASM_OPERANDS:
        !          1281:       if (MEM_VOLATILE_P (x))
        !          1282:        return 1;
        !          1283:     }
        !          1284: 
        !          1285:   /* Recursively scan the operands of this expression.  */
        !          1286: 
        !          1287:   {
        !          1288:     register char *fmt = GET_RTX_FORMAT (code);
        !          1289:     register int i;
        !          1290:     
        !          1291:     for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
        !          1292:       {
        !          1293:        if (fmt[i] == 'e')
        !          1294:          {
        !          1295:            if (side_effects_p (XEXP (x, i)))
        !          1296:              return 1;
        !          1297:          }
        !          1298:        if (fmt[i] == 'E')
        !          1299:          {
        !          1300:            register int j;
        !          1301:            for (j = 0; j < XVECLEN (x, i); j++)
        !          1302:              if (side_effects_p (XVECEXP (x, i, j)))
        !          1303:                return 1;
        !          1304:          }
        !          1305:       }
        !          1306:   }
        !          1307:   return 0;
        !          1308: }
        !          1309: 
        !          1310: /* Return nonzero if evaluating rtx X might cause a trap.  */
        !          1311: 
        !          1312: int
        !          1313: may_trap_p (x)
        !          1314:      rtx x;
        !          1315: {
        !          1316:   int i;
        !          1317:   enum rtx_code code;
        !          1318:   char *fmt;
        !          1319: 
        !          1320:   if (x == 0)
        !          1321:     return 0;
        !          1322:   code = GET_CODE (x);
        !          1323:   switch (code)
        !          1324:     {
        !          1325:       /* Handle these cases quickly.  */
        !          1326:     case CONST_INT:
        !          1327:     case CONST_DOUBLE:
        !          1328:     case SYMBOL_REF:
        !          1329:     case LABEL_REF:
        !          1330:     case CONST:
        !          1331:     case PC:
        !          1332:     case CC0:
        !          1333:     case REG:
        !          1334:     case SCRATCH:
        !          1335:       return 0;
        !          1336: 
        !          1337:       /* Conditional trap can trap!  */
        !          1338:     case UNSPEC_VOLATILE:
        !          1339:     case TRAP_IF:
        !          1340:       return 1;
        !          1341: 
        !          1342:       /* Memory ref can trap unless it's a static var or a stack slot.  */
        !          1343:     case MEM:
        !          1344:       return rtx_addr_can_trap_p (XEXP (x, 0));
        !          1345: 
        !          1346:       /* Division by a non-constant might trap.  */
        !          1347:     case DIV:
        !          1348:     case MOD:
        !          1349:     case UDIV:
        !          1350:     case UMOD:
        !          1351:       if (! CONSTANT_P (XEXP (x, 1)))
        !          1352:        return 1;
        !          1353:       /* This was const0_rtx, but by not using that,
        !          1354:         we can link this file into other programs.  */
        !          1355:       if (GET_CODE (XEXP (x, 1)) == CONST_INT && INTVAL (XEXP (x, 1)) == 0)
        !          1356:        return 1;
        !          1357:     default:
        !          1358:       /* Any floating arithmetic may trap.  */
        !          1359:       if (GET_MODE_CLASS (GET_MODE (x)) == MODE_FLOAT)
        !          1360:        return 1;
        !          1361:     }
        !          1362: 
        !          1363:   fmt = GET_RTX_FORMAT (code);
        !          1364:   for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
        !          1365:     {
        !          1366:       if (fmt[i] == 'e')
        !          1367:        {
        !          1368:          if (may_trap_p (XEXP (x, i)))
        !          1369:            return 1;
        !          1370:        }
        !          1371:       else if (fmt[i] == 'E')
        !          1372:        {
        !          1373:          register int j;
        !          1374:          for (j = 0; j < XVECLEN (x, i); j++)
        !          1375:            if (may_trap_p (XVECEXP (x, i, j)))
        !          1376:              return 1;
        !          1377:        }
        !          1378:     }
        !          1379:   return 0;
        !          1380: }
        !          1381: 
        !          1382: /* Return nonzero if X contains a comparison that is not either EQ or NE,
        !          1383:    i.e., an inequality.  */
        !          1384: 
        !          1385: int
        !          1386: inequality_comparisons_p (x)
        !          1387:      rtx x;
        !          1388: {
        !          1389:   register char *fmt;
        !          1390:   register int len, i;
        !          1391:   register enum rtx_code code = GET_CODE (x);
        !          1392: 
        !          1393:   switch (code)
        !          1394:     {
        !          1395:     case REG:
        !          1396:     case SCRATCH:
        !          1397:     case PC:
        !          1398:     case CC0:
        !          1399:     case CONST_INT:
        !          1400:     case CONST_DOUBLE:
        !          1401:     case CONST:
        !          1402:     case LABEL_REF:
        !          1403:     case SYMBOL_REF:
        !          1404:       return 0;
        !          1405: 
        !          1406:     case LT:
        !          1407:     case LTU:
        !          1408:     case GT:
        !          1409:     case GTU:
        !          1410:     case LE:
        !          1411:     case LEU:
        !          1412:     case GE:
        !          1413:     case GEU:
        !          1414:       return 1;
        !          1415:     }
        !          1416: 
        !          1417:   len = GET_RTX_LENGTH (code);
        !          1418:   fmt = GET_RTX_FORMAT (code);
        !          1419: 
        !          1420:   for (i = 0; i < len; i++)
        !          1421:     {
        !          1422:       if (fmt[i] == 'e')
        !          1423:        {
        !          1424:          if (inequality_comparisons_p (XEXP (x, i)))
        !          1425:            return 1;
        !          1426:        }
        !          1427:       else if (fmt[i] == 'E')
        !          1428:        {
        !          1429:          register int j;
        !          1430:          for (j = XVECLEN (x, i) - 1; j >= 0; j--)
        !          1431:            if (inequality_comparisons_p (XVECEXP (x, i, j)))
        !          1432:              return 1;
        !          1433:        }
        !          1434:     }
        !          1435:            
        !          1436:   return 0;
        !          1437: }
        !          1438: 
        !          1439: /* Replace any occurrence of FROM in X with TO.
        !          1440: 
        !          1441:    Note that copying is not done so X must not be shared unless all copies
        !          1442:    are to be modified.  */
        !          1443: 
        !          1444: rtx
        !          1445: replace_rtx (x, from, to)
        !          1446:      rtx x, from, to;
        !          1447: {
        !          1448:   register int i, j;
        !          1449:   register char *fmt;
        !          1450: 
        !          1451:   if (x == from)
        !          1452:     return to;
        !          1453: 
        !          1454:   /* Allow this function to make replacements in EXPR_LISTs.  */
        !          1455:   if (x == 0)
        !          1456:     return 0;
        !          1457: 
        !          1458:   fmt = GET_RTX_FORMAT (GET_CODE (x));
        !          1459:   for (i = GET_RTX_LENGTH (GET_CODE (x)) - 1; i >= 0; i--)
        !          1460:     {
        !          1461:       if (fmt[i] == 'e')
        !          1462:        XEXP (x, i) = replace_rtx (XEXP (x, i), from, to);
        !          1463:       else if (fmt[i] == 'E')
        !          1464:        for (j = XVECLEN (x, i) - 1; j >= 0; j--)
        !          1465:          XVECEXP (x, i, j) = replace_rtx (XVECEXP (x, i, j), from, to);
        !          1466:     }
        !          1467: 
        !          1468:   return x;
        !          1469: }  
        !          1470: 
        !          1471: /* Throughout the rtx X, replace many registers according to REG_MAP.
        !          1472:    Return the replacement for X (which may be X with altered contents).
        !          1473:    REG_MAP[R] is the replacement for register R, or 0 for don't replace.
        !          1474:    NREGS is the length of REG_MAP; regs >= NREGS are not mapped.  
        !          1475: 
        !          1476:    We only support REG_MAP entries of REG or SUBREG.  Also, hard registers
        !          1477:    should not be mapped to pseudos or vice versa since validate_change
        !          1478:    is not called.
        !          1479: 
        !          1480:    If REPLACE_DEST is 1, replacements are also done in destinations;
        !          1481:    otherwise, only sources are replaced.  */
        !          1482: 
        !          1483: rtx
        !          1484: replace_regs (x, reg_map, nregs, replace_dest)
        !          1485:      rtx x;
        !          1486:      rtx *reg_map;
        !          1487:      int nregs;
        !          1488:      int replace_dest;
        !          1489: {
        !          1490:   register enum rtx_code code;
        !          1491:   register int i;
        !          1492:   register char *fmt;
        !          1493: 
        !          1494:   if (x == 0)
        !          1495:     return x;
        !          1496: 
        !          1497:   code = GET_CODE (x);
        !          1498:   switch (code)
        !          1499:     {
        !          1500:     case SCRATCH:
        !          1501:     case PC:
        !          1502:     case CC0:
        !          1503:     case CONST_INT:
        !          1504:     case CONST_DOUBLE:
        !          1505:     case CONST:
        !          1506:     case SYMBOL_REF:
        !          1507:     case LABEL_REF:
        !          1508:       return x;
        !          1509: 
        !          1510:     case REG:
        !          1511:       /* Verify that the register has an entry before trying to access it.  */
        !          1512:       if (REGNO (x) < nregs && reg_map[REGNO (x)] != 0)
        !          1513:        return reg_map[REGNO (x)];
        !          1514:       return x;
        !          1515: 
        !          1516:     case SUBREG:
        !          1517:       /* Prevent making nested SUBREGs.  */
        !          1518:       if (GET_CODE (SUBREG_REG (x)) == REG && REGNO (SUBREG_REG (x)) < nregs
        !          1519:          && reg_map[REGNO (SUBREG_REG (x))] != 0
        !          1520:          && GET_CODE (reg_map[REGNO (SUBREG_REG (x))]) == SUBREG)
        !          1521:        {
        !          1522:          rtx map_val = reg_map[REGNO (SUBREG_REG (x))];
        !          1523:          rtx map_inner = SUBREG_REG (map_val);
        !          1524: 
        !          1525:          if (GET_MODE (x) == GET_MODE (map_inner))
        !          1526:            return map_inner;
        !          1527:          else
        !          1528:            {
        !          1529:              /* We cannot call gen_rtx here since we may be linked with
        !          1530:                 genattrtab.c.  */
        !          1531:              /* Let's try clobbering the incoming SUBREG and see
        !          1532:                 if this is really safe.  */
        !          1533:              SUBREG_REG (x) = map_inner;
        !          1534:              SUBREG_WORD (x) += SUBREG_WORD (map_val);
        !          1535:              return x;
        !          1536: #if 0
        !          1537:              rtx new = rtx_alloc (SUBREG);
        !          1538:              PUT_MODE (new, GET_MODE (x));
        !          1539:              SUBREG_REG (new) = map_inner;
        !          1540:              SUBREG_WORD (new) = SUBREG_WORD (x) + SUBREG_WORD (map_val);
        !          1541: #endif
        !          1542:            }
        !          1543:        }
        !          1544:       break;
        !          1545: 
        !          1546:     case SET:
        !          1547:       if (replace_dest)
        !          1548:        SET_DEST (x) = replace_regs (SET_DEST (x), reg_map, nregs, 0);
        !          1549: 
        !          1550:       else if (GET_CODE (SET_DEST (x)) == MEM
        !          1551:               || GET_CODE (SET_DEST (x)) == STRICT_LOW_PART)
        !          1552:        /* Even if we are not to replace destinations, replace register if it
        !          1553:           is CONTAINED in destination (destination is memory or
        !          1554:           STRICT_LOW_PART).  */
        !          1555:        XEXP (SET_DEST (x), 0) = replace_regs (XEXP (SET_DEST (x), 0),
        !          1556:                                               reg_map, nregs, 0);
        !          1557:       else if (GET_CODE (SET_DEST (x)) == ZERO_EXTRACT)
        !          1558:        /* Similarly, for ZERO_EXTRACT we replace all operands.  */
        !          1559:        break;
        !          1560: 
        !          1561:       SET_SRC (x) = replace_regs (SET_SRC (x), reg_map, nregs, 0);
        !          1562:       return x;
        !          1563:     }
        !          1564: 
        !          1565:   fmt = GET_RTX_FORMAT (code);
        !          1566:   for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
        !          1567:     {
        !          1568:       if (fmt[i] == 'e')
        !          1569:        XEXP (x, i) = replace_regs (XEXP (x, i), reg_map, nregs, replace_dest);
        !          1570:       if (fmt[i] == 'E')
        !          1571:        {
        !          1572:          register int j;
        !          1573:          for (j = 0; j < XVECLEN (x, i); j++)
        !          1574:            XVECEXP (x, i, j) = replace_regs (XVECEXP (x, i, j), reg_map,
        !          1575:                                              nregs, replace_dest);
        !          1576:        }
        !          1577:     }
        !          1578:   return x;
        !          1579: }

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