99 lines
2.2 KiB
C
99 lines
2.2 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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/*
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ROUTINE TO MULTIPLY TWO EXTENDED FORMAT NUMBERS
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*/
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# include "FP_bias.h"
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# include "FP_trap.h"
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# include "FP_types.h"
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# include "FP_shift.h"
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void
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mul_ext(e1,e2)
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EXTEND *e1,*e2;
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{
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register int i,j; /* loop control */
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unsigned short mp[4]; /* multiplier */
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unsigned short mc[4]; /* multipcand */
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unsigned short result[8]; /* result */
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register unsigned short *pres;
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/* first save the sign (XOR) */
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e1->sign ^= e2->sign;
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/* compute new exponent */
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e1->exp += e2->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;
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mp[1] = (unsigned short) e1->m1;
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mp[2] = e1->m2 >> 16;
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mp[3] = (unsigned short) e1->m2;
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mc[0] = e2->m1 >> 16;
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mc[1] = (unsigned short) e2->m1;
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mc[2] = e2->m2 >> 16;
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mc[3] = (unsigned short) e2->m2;
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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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unsigned long mpi = mp[i];
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for(j=4;j--;) {
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unsigned long tmp = (unsigned long)pres[j] + k;
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if (mc[j]) tmp += mpi * mc[j];
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pres[j] = tmp;
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k = tmp >> 16;
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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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e1->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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e1->m1 = ((unsigned long)(result[0]) << 16) + result[1];
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e1->m2 = ((unsigned long)(result[2]) << 16) + result[3];
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if (result[4] & 0x8000) {
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if (++e1->m2 == 0)
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if (++e1->m1 == 0) {
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e1->m1 = NORMBIT;
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e1->exp++;
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}
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}
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/* check for overflow */
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if (e1->exp >= EXT_MAX) {
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trap(EFOVFL);
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/* if caught */
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/* return signed infinity */
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e1->exp = EXT_MAX;
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infinity: e1->m1 = e1->m2 =0L;
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return;
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}
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/* check for underflow */
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if (e1->exp < EXT_MIN) {
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trap(EFUNFL);
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e1->exp = EXT_MIN;
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goto infinity;
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}
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}
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