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Annotation of pgp/src/r3000.c, revision 1.1.1.3

1.1.1.3 ! root        1: /*     r3000.c - MIPS R3000 adaptation of selected routines from mpilib.c.
        !             2: 
        !             3:        C source code for multiprecision arithmetic library routines.
        !             4:        R3000 optimizations by Castor Fu, in Sep 1992.
        !             5:        See the comments in the file mpilib.c for details on the purpose of
        !             6:        these functions.
        !             7: 
        !             8:        Original version of mpilib.c implemented in 1986 by 
        !             9:        Philip R. Zimmermann, updated by PRZ 1990-1992.
        !            10: 
        !            11:        Boulder Software Engineering
        !            12:        3021 Eleventh Street
        !            13:        Boulder, CO 80304
        !            14:        (303) 541-0140
        !            15: 
        !            16:        (c) Copyright 1990-1994 by Philip Zimmermann.  All rights reserved.
        !            17:        The author assumes no liability for damages resulting from the use
        !            18:        of this software, even if the damage results from defects in this
        !            19:        software.  No warranty is expressed or implied.
        !            20: 
        !            21:        Note that while most PGP source modules bear Philip Zimmermann's
        !            22:        copyright notice, many of them have been revised or entirely written
        !            23:        by contributors who frequently failed to put their names in their
        !            24:        code.  Code that has been incorporated into PGP from other authors
        !            25:        was either originally published in the public domain or is used with
        !            26:        permission from the various authors.
        !            27: 
        !            28:        PGP is available for free to the public under certain restrictions.
        !            29:        See the PGP User's Guide (included in the release package) for
        !            30:        important information about licensing, patent restrictions on
        !            31:        certain algorithms, trademarks, copyrights, and export controls.
        !            32: 
        !            33:        -- Adapt so that the unit size can be a full int size. This
        !            34:           was inspired by the lack of a carry bit on MIPSco processors.
        !            35:           On such machines, the advantage of assembly language coding
        !            36:           is less clear.  (Except for the multiply. . . )
        !            37: 
        !            38:           One reason for creating an R3000 module of C routines is that
        !            39:           we have one routine (P_ROTL) which is compiled particularly
        !            40:           poorly, and chose to explicitly unroll the loop.
        !            41: 
        !            42: */
        !            43: 
        !            44: 
        !            45: #include "mpilib.h"
        !            46: 
        !            47: #define word_v(r,n)    (r)[tohigher(n)]
        !            48: 
        !            49: extern short global_precision; /* units of precision for all routines */
        !            50: /*     global_precision is the unit precision last set by set_precision.
        !            51:        Initially, set_precision() should be called to define global_precision
        !            52:        before using any of these other multiprecision library routines.
        !            53:        i.e.:   set_precision(MAX_UNIT_PRECISION);
        !            54: */
        !            55: 
        !            56: /*************** multiprecision library primitives ****************/
        !            57: /*     The following portable C primitives should be recoded in assembly.
        !            58:        The equivalent assembly primitives are externally defined under
        !            59:        different names, unless PORTABLE is defined.  See the header file
        !            60:        "mpilib.h" for further details.
        !            61: */
        !            62: 
        !            63: typedef unsigned long int ulint;
        !            64: /* ...assumes sizeof(unit) <= sizeof(unsigned long) */
        !            65: 
        !            66: boolean mp_addc
        !            67:        (register unitptr r1,register unitptr r2,register boolean carry)
        !            68:        /* multiprecision add with carry r2 to r1, result in r1 */
        !            69:        /* carry is incoming carry flag-- value should be 0 or 1 */
        !            70: {
        !            71:        register unit x,x1;
        !            72:        int i;
        !            73:        short precision;        /* number of units to add */
        !            74:        unsigned int mcarry = carry;
        !            75:        precision = global_precision;
        !            76:        make_lsbptr(r1,precision);
        !            77:        make_lsbptr(r2,precision);
        !            78: 
        !            79:        i = precision&3;
        !            80:        while (i--) {   
        !            81:                  if (mcarry) {
        !            82:                     x = *r1 + *r2 + 1;
        !            83:                     x1 = ~ *r1;
        !            84:                     mcarry = 1 ^ (*r2  < x1);
        !            85:                  } else {
        !            86:                     x = *r1 + *r2;
        !            87:                     mcarry = (x < *r1) ;
        !            88:                  }
        !            89:                post_higherunit(r2);
        !            90:                *post_higherunit(r1) = x;
        !            91:        }
        !            92: 
        !            93:        i = precision>>2;
        !            94:        while (i--) {   
        !            95: #define ADDC(n) \
        !            96:                  if (mcarry) { \
        !            97:                     x = word_v(r1,n) + word_v(r2,n) + 1; \
        !            98:                     x1 = ~word_v(r1,n); \
        !            99:                     mcarry = 1 ^ (word_v(r2,n)  < x1); \
        !           100:                  } else { \
        !           101:                     x = word_v(r1,n) + word_v(r2,n); \
        !           102:                     mcarry = (x < word_v(r1,n)) ; \
        !           103:                  } \
        !           104:                  word_v(r1,n) = x;
        !           105: 
        !           106:                  ADDC(0);
        !           107:                  ADDC(1);
        !           108:                  ADDC(2);
        !           109:                  ADDC(3);
        !           110: #undef ADDC
        !           111:                r1 += tohigher(4);
        !           112:                r2 += tohigher(4);
        !           113:        }
        !           114: 
        !           115:        return(mcarry);         /* return the final carry flag bit */
        !           116: }      /* mp_addc */
        !           117: 
        !           118: 
        !           119: boolean mp_subb
        !           120:        (register unitptr r1,register unitptr r2,register boolean borrow)
        !           121:        /* multiprecision subtract with borrow, r2 from r1, result in r1 */
        !           122:        /* borrow is incoming borrow flag-- value should be 0 or 1 */
        !           123: {
        !           124:        register unit x;        
        !           125:        unsigned int mborrow = borrow;
        !           126:        int i; 
        !           127:        short precision;        /* number of units to subtract */
        !           128:        precision = global_precision;
        !           129:        make_lsbptr(r1,precision);
        !           130:        make_lsbptr(r2,precision);
        !           131: 
        !           132:        i = precision&3;
        !           133:        while (i--) {
        !           134:                if (mborrow) {
        !           135:                  x = *r1 - *r2 - mborrow;
        !           136:                  mborrow = 1 ^ (*r2 < *r1);
        !           137:                } else {
        !           138:                  x = *r1 - *r2;
        !           139:                  mborrow = (*r1 < *r2);
        !           140:                }
        !           141:                post_higherunit(r2);
        !           142:                *post_higherunit(r1) = x;
        !           143:        }
        !           144: 
        !           145:        i = precision>>2;
        !           146:        while (i--) {   
        !           147: 
        !           148: #define        SUBB(n) \
        !           149:                if (mborrow) { \
        !           150:                  x = word_v(r1,n) - word_v(r2,n) - mborrow; \
        !           151:                  mborrow = 1 ^ (word_v(r2,n) < word_v(r1,n)); \
        !           152:                } else { \
        !           153:                  x = word_v(r1,n) - word_v(r2,n); \
        !           154:                  mborrow = (word_v(r1,n) < word_v(r2,n)); \
        !           155:                } \
        !           156:                word_v(r1,n) = x;
        !           157: 
        !           158:                SUBB(0);
        !           159:                SUBB(1);
        !           160:                SUBB(2);
        !           161:                SUBB(3);
        !           162: #undef SUBB
        !           163: 
        !           164: 
        !           165:                r1 += tohigher(4);
        !           166:                r2 += tohigher(4);
        !           167:        }
        !           168: 
        !           169:        return(mborrow);        /* return the final carry/borrow flag bit */
        !           170: }      /* mp_subb */
        !           171: 
        !           172: 
        !           173: /* We've unrolled the loop here because the MIPS/DEC C compiler is too
        !           174:  * stupid to do so.  Presumably on register poor machines this is not
        !           175:  * a clearly good idea
        !           176:  */
        !           177: 
        !           178: boolean mp_rotate_left(register unitptr r1,register boolean carry)
        !           179:        /* multiprecision rotate left 1 bit with carry, result in r1. */
        !           180:        /* carry is incoming carry flag-- value should be 0 or 1 */
        !           181: {
        !           182:        register int precision; /* number of units to rotate */
        !           183:        unsigned int mcarry = carry, carry2,carry3,carry4, nextcarry; 
        !           184: 
        !           185:        int i;
        !           186:        precision = global_precision;
        !           187:        make_lsbptr(r1,precision);
        !           188:        i = precision &3;
        !           189:        while (i--) {
        !           190:                nextcarry = (((signedunit) *r1) < 0);
        !           191:                *r1 = (*r1 << 1) | mcarry;
        !           192:                mcarry = nextcarry;
        !           193:                pre_higherunit(r1);
        !           194:        }
        !           195:        i = precision>>2;
        !           196:        while (i--) {
        !           197:                carry2 = (((signedunit) *r1) < 0);
        !           198:                *r1 = (*r1 << 1) | mcarry;
        !           199: 
        !           200:                carry3 = (((signedunit) word_v(r1,1)) < 0);
        !           201:                word_v(r1,1) = (word_v(r1,1) << 1) | carry2;
        !           202: 
        !           203:                carry4 = (((signedunit) word_v(r1,2)) < 0);
        !           204:                word_v(r1,2) = (word_v(r1,2) << 1) | carry3;
        !           205: 
        !           206:                mcarry = (((signedunit) word_v(r1,3)) < 0);
        !           207:                word_v(r1,3) = (word_v(r1,3) << 1) | carry4;
        !           208: 
        !           209:                r1 += tohigher(4);
        !           210:        }
        !           211:        return(mcarry); /* return the final carry flag bit */
        !           212: }      /* mp_rotate_left */
        !           213: 
        !           214: void p_setp(short nbits){} 
        !           215: 
        !           216: /************** end of primitives that should be in assembly *************/
        !           217: 
        !           218: #include "lmul.h"      /* used only by R3000.c */
        !           219: 
        !           220: #ifdef MUNIT16
        !           221: typedef unsigned short MULTUNIT;
        !           222: #endif
        !           223: 
        !           224: #ifdef MUNIT32
        !           225: typedef unsigned int MULTUNIT;
        !           226: #endif
        !           227: #define        MULTUNITSIZE    (sizeof(MULTUNIT)*8)
        !           228: #define MULTUNIT_hmask ((1UL << (MULTUNITSIZE/2))-1)
        !           229: #define MULTUNIT_mask   ((MULTUNIT_hmask<<(MULTUNITSIZE/2)) | MULTUNIT_hmask)
        !           230: 
        !           231: void p_smula (
        !           232: MULTUNIT *prod,
        !           233: MULTUNIT *multiplicand,
        !           234: MULTUNIT multiplier)
        !           235: {
        !           236:        short i=global_precision;
        !           237:        int count=i,j;
        !           238:        MULTUNIT *pp=prod, *mp=multiplicand;  
        !           239:        MULTUNIT pl, ph, npl, nph, cl, ch;
        !           240:        MULTUNIT al, ah;
        !           241: 
        !           242:        cl = 0;
        !           243:        ch = 0;
        !           244:        
        !           245:        if (i <= 0 ) return;
        !           246:        lmul(multiplier, *multiplicand, pl, ph);
        !           247:        post_higherunit(multiplicand);
        !           248:        al = 0;
        !           249:        ah = 0;
        !           250:        ch = 0;
        !           251:        while(--i) {
        !           252:                lmul(multiplier, *multiplicand, npl, nph);
        !           253:                post_higherunit(multiplicand);
        !           254:                al += *prod;
        !           255:                cl = (al < *prod);
        !           256:                al += pl;
        !           257:                cl += (al < pl);
        !           258:                ah += ph;
        !           259:                ch = (ah < ph);
        !           260:                ah += cl;
        !           261:                ch += (ah < cl);
        !           262:                *prod = al;
        !           263:                post_higherunit(prod);
        !           264:                al = ah;
        !           265:                ah = ch;
        !           266:                pl = npl;
        !           267:                ph = nph;
        !           268:        }
        !           269:        al += *prod;
        !           270:        cl = (al < *prod);
        !           271:        al += pl;
        !           272:        cl += (al < pl);
        !           273:        ah += ph;
        !           274:        ch = (ah < ph);
        !           275:        ah += cl;
        !           276:        ch += (ah < cl);
        !           277: 
        !           278:        *prod = al;
        !           279:        post_higherunit(prod);
        !           280: 
        !           281:        *prod += ah;
        !           282:        ch += (*prod < ah);
        !           283:        post_higherunit(prod);
        !           284: 
        !           285:        /*
        !           286:        *prod += ch ;
        !           287:        post_higherunit(prod);
        !           288:        */
        !           289: 
        !           290: 
        !           291: }      /* mp_smul */
        !           292: 
        !           293: 
        !           294: 
        !           295: static  int  mshift;                   /* number of bits for
        !           296:                                        ** recip scaling          */
        !           297: static  MULTUNIT reciph;               /* MSunit of scaled recip */
        !           298: static  MULTUNIT recipl;               /* LSunit of scaled recip */
        !           299: 
        !           300: void p_setrecip(MULTUNIT rh, MULTUNIT rl, int m)
        !           301: {
        !           302:        reciph = rh;
        !           303:        recipl = rl;
        !           304:        mshift = m;
        !           305: }
        !           306: 
        !           307: 
        !           308: MULTUNIT p_quo_digit (MULTUNIT *dividend) 
        !           309: {
        !           310:        MULTUNIT ql, qh, q0l, q0h, q1l, q1h, q2l, q2h;
        !           311:        MULTUNIT q3h, q3l, q4h, q4l;
        !           312:        MULTUNIT mutemp;
        !           313: 
        !           314: 
        !           315: /*     Compute the least significant product group.
        !           316:        The last terms of q1 and q2 perform upward rounding, which is
        !           317:        needed to guarantee that the result not be too small.
        !           318: */
        !           319:        lmul(dividend[tohigher(-2)] ^ MULTUNIT_mask, reciph, q1l, q1h);
        !           320:        q1l += reciph;
        !           321:        q1h += (q1l <  reciph);
        !           322: 
        !           323:        lmul(dividend[tohigher(-1)]^ MULTUNIT_mask, recipl, q2l, q2h);
        !           324:        q2h += 1;
        !           325: 
        !           326:        q1l = (q1l >> 1) + (q1h << (MULTUNITSIZE-1));
        !           327:        q1h >>= 1;
        !           328:        q2l =  (q2l >> 1) + (q2h << (MULTUNITSIZE-1));
        !           329:        q2h >>= 1;
        !           330: 
        !           331:        q0l = q1l + q2l;
        !           332:        q0h = q1h + q2h + (q0l < q1l);
        !           333: 
        !           334:        q0l++;
        !           335:        q0h+= (q0l < 1);
        !           336: 
        !           337: /*     Compute the middle significant product group.   */
        !           338: 
        !           339:        lmul(dividend[tohigher(-1)]^MULTUNIT_mask, reciph, q3l, q3h);
        !           340:        lmul(dividend[0] ^ MULTUNIT_mask, recipl,  q4l, q4h);
        !           341: 
        !           342:        q3l = (q3l >> 1) + (q3h << (MULTUNITSIZE-1));
        !           343:        q3h >>= 1;
        !           344:        q4l =  (q4l >> 1) + (q4h << (MULTUNITSIZE-1));
        !           345:        q4h >>= 1;
        !           346: 
        !           347:        ql = q0h + 1;
        !           348:        qh = (ql < 1);
        !           349: 
        !           350:        ql += q3l;
        !           351:        qh += q3h + (ql < q3l);
        !           352:        ql += q4l;
        !           353:        qh += q4h + (ql < q4l);
        !           354: 
        !           355: /*     Compute the most significant term and add in the others */
        !           356: 
        !           357:        lmul((dividend[0] ^ MULTUNIT_mask), reciph, q1l, q1h);
        !           358:        q1h = (q1h << 1) + (q1l>>(MULTUNITSIZE-1));
        !           359:        q1l = (q1l << 1) ;
        !           360: 
        !           361:        ql = (ql >> (MULTUNITSIZE-2)) + (qh <<  2);
        !           362:        qh >>= (MULTUNITSIZE-2);
        !           363: 
        !           364:        ql += q1l;
        !           365:        qh += (ql < q1l) + q1h;
        !           366: 
        !           367:        if (mshift != MULTUNITSIZE) {
        !           368:                ql = (ql >> mshift) + (qh << (MULTUNITSIZE-mshift));
        !           369:                qh >>= mshift;
        !           370:        } else {
        !           371:                ql = qh;
        !           372:                qh  = 0;
        !           373:        }
        !           374: 
        !           375: /*     Prevent overflow and then wipe out the intermediate results. */
        !           376:        mutemp = (qh != 0) ?  MULTUNIT_mask : ql;
        !           377: 
        !           378:        return(mutemp);
        !           379: }
        !           380: 
        !           381: /* end of r3000.c */
        !           382: 

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