85 lines
1.8 KiB
C
85 lines
1.8 KiB
C
/*
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(c) copyright 1988 by the Vrije Universiteit, Amsterdam, The Netherlands.
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See the copyright notice in the ACK home directory, in the file "Copyright".
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*/
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/* $Header$ */
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#include "misc.h"
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flt_mul(e1,e2,e3)
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register flt_arith *e1,*e2,*e3;
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{
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/* Multiply the extended numbers e1 and e2, and put the
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result in e3.
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*/
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register int i,j; /* loop control */
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unsigned short mp[4];
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unsigned short mc[4];
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unsigned short result[8]; /* result */
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register unsigned short *pres;
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flt_status = 0;
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/* first save the sign (XOR) */
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e3->flt_sign = e1->flt_sign ^ e2->flt_sign;
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/* compute new exponent */
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e3->flt_exp = e1->flt_exp + e2->flt_exp + 1;
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/* 128 bit multiply of mantissas */
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/* assign unknown long formats */
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/* to known unsigned word formats */
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mp[0] = (e1->m1 >> 16) & 0xFFFF;
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mp[1] = e1->m1 & 0xFFFF;
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mp[2] = (e1->m2 >> 16) & 0xFFFF;
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mp[3] = e1->m2 & 0xFFFF;
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mc[0] = (e2->m1 >> 16) & 0xFFFF;
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mc[1] = e2->m1 & 0xFFFF;
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mc[2] = (e2->m2 >> 16) & 0xFFFF;
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mc[3] = e2->m2 & 0xFFFF;
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for (i = 8; i--;) {
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result[i] = 0;
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}
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/*
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* fill registers with their components
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*/
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for(i=4, pres = &result[4];i--;pres--) if (mp[i]) {
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unsigned short k = 0;
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long mpi = mp[i];
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for(j=4;j--;) {
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long tmp = (long)pres[j] + k;
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if (mc[j]) tmp += mpi * mc[j];
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pres[j] = tmp & 0xFFFF;
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k = (tmp >> 16) & 0xFFFF;
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}
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pres[-1] = k;
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}
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if (! (result[0] & 0x8000)) {
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e3->flt_exp--;
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for (i = 0; i <= 3; i++) {
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result[i] <<= 1;
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if (result[i+1]&0x8000) result[i] |= 1;
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}
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result[4] <<= 1;
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}
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/*
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* combine the registers to a total
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*/
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e3->m1 = ((long)result[0] << 16) + result[1];
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e3->m2 = ((long)result[2] << 16) + result[3];
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if (result[4] & 0x8000) {
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if (++e3->m2 == 0 || (e3->m2 & ~ 0xFFFFFFFF)) {
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e3->m2 = 0;
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if (++e3->m1 == 0 || (e3->m1 & ~ 0xFFFFFFFF)) {
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e3->m1 = 0x80000000;
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e3->flt_exp++;
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}
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}
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}
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flt_chk(e3);
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}
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