202 lines
4 KiB
Text
202 lines
4 KiB
Text
/*
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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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COMPACT EXTEND FORMAT INTO FLOAT OF PROPER SIZE
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*/
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# include "FP_bias.h"
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# include "FP_shift.h"
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# include "FP_trap.h"
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# include "FP_types.h"
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# include "get_put.h"
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void
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compact(f,to,size)
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EXTEND *f;
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unsigned long *to;
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int size;
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{
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int error = 0;
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if (size == sizeof(DOUBLE)) {
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/*
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* COMPACT EXTENDED INTO DOUBLE
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*/
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DOUBLE *DBL = (DOUBLE *) (void *) to;
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if ((f->m1|(f->m2 & DBL_ZERO)) == 0L) {
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zrf8(DBL);
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return;
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}
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f->exp += DBL_BIAS; /* restore proper bias */
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if (f->exp > DBL_MAX) {
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dbl_over: trap(EFOVFL);
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f->exp = DBL_MAX+1;
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f->m1 = 0;
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f->m2 = 0;
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if (error++)
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return;
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}
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else if (f->exp < DBL_MIN) {
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b64_rsft(&(f->mantissa));
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if (f->exp < 0) {
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b64_sft(&(f->mantissa), -f->exp);
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f->exp = 0;
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}
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/* underflow ??? */
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}
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/* local CAST conversion */
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/* because of special format shift only 10 bits */
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/* bit shift mantissa 10 bits */
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/* first align within words, then do store operation */
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DBL->d[0] = f->m1 >> DBL_RUNPACK; /* plus 22 == 32 */
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DBL->d[1] = f->m2 >> DBL_RUNPACK; /* plus 22 == 32 */
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DBL->d[1] |= (f->m1 << DBL_LUNPACK); /* plus 10 == 32 */
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/* if not exact then round to nearest */
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/* on a tie, round to even */
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#ifdef EXCEPTION_INEXACT
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if ((f->m2 & DBL_EXACT) != 0) {
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INEXACT();
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#endif
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if (((f->m2 & DBL_EXACT) > DBL_ROUNDUP)
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|| ((f->m2 & DBL_EXACT) == DBL_ROUNDUP
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&& (f->m2 & (DBL_ROUNDUP << 1)))) {
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DBL->d[1]++; /* rounding up */
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if (DBL->d[1] == 0L) { /* carry out */
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DBL->d[0]++;
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if (f->exp == 0 && (DBL->d[0] & ~DBL_MASK)) {
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f->exp++;
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}
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if (DBL->d[0] & DBL_CARRYOUT) { /* carry out */
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if (DBL->d[0] & 01)
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DBL->d[1] = CARRYBIT;
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DBL->d[0] >>= 1;
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f->exp++;
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}
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}
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/* check for overflow */
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if (f->exp > DBL_MAX)
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goto dbl_over;
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}
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#ifdef EXCEPTION_INEXACT
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}
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#endif
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/*
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* STORE EXPONENT AND SIGN:
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*
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* 1) clear leading bits (B4-B15)
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* 2) shift and store exponent
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*/
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DBL->d[0] &= DBL_MASK;
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DBL->d[0] |=
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((long) (f->exp << DBL_EXPSHIFT) << EXP_STORE);
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if (f->sign)
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DBL->d[0] |= CARRYBIT;
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/*
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* STORE MANTISSA
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*/
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#if FL_MSL_AT_LOW_ADDRESS
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put4(DBL->d[0], (char *) &DBL->d[0]);
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put4(DBL->d[1], (char *) &DBL->d[1]);
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#else
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{ unsigned long l;
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put4(DBL->d[1], (char *) &l);
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put4(DBL->d[0], (char *) &DBL->d[1]);
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DBL->d[0] = l;
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}
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#endif
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}
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else {
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/*
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* COMPACT EXTENDED INTO FLOAT
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*/
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SINGLE *SGL;
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/* local CAST conversion */
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SGL = (SINGLE *) (void *) to;
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if ((f->m1 & SGL_ZERO) == 0L) {
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*SGL = 0L;
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return;
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}
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f->exp += SGL_BIAS; /* restore bias */
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if (f->exp > SGL_MAX) {
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sgl_over: trap(EFOVFL);
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f->exp = SGL_MAX+1;
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f->m1 = 0L;
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f->m2 = 0L;
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if (error++)
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return;
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}
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else if (f->exp < SGL_MIN) {
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b64_rsft(&(f->mantissa));
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if (f->exp < 0) {
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b64_sft(&(f->mantissa), -f->exp);
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f->exp = 0;
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}
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/* underflow ??? */
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}
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/* shift mantissa and store */
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*SGL = (f->m1 >> SGL_RUNPACK);
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/* check for rounding to nearest */
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/* on a tie, round to even */
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#ifdef EXCEPTION_INEXACT
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if (f->m2 != 0 ||
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(f->m1 & SGL_EXACT) != 0L) {
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INEXACT();
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#endif
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if (((f->m1 & SGL_EXACT) > SGL_ROUNDUP)
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|| ((f->m1 & SGL_EXACT) == SGL_ROUNDUP
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&& (f->m1 & (SGL_ROUNDUP << 1)))) {
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(*SGL)++;
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if (f->exp == 0 && (*SGL & ~SGL_MASK)) {
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f->exp++;
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}
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/* check normal */
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if (*SGL & SGL_CARRYOUT) {
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*SGL >>= 1;
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f->exp++;
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}
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if (f->exp > SGL_MAX)
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goto sgl_over;
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}
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#ifdef EXCEPTION_INEXACT
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}
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#endif
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/*
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* STORE EXPONENT AND SIGN:
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*
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* 1) clear leading bit of fraction
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* 2) shift and store exponent
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*/
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*SGL &= SGL_MASK; /* B23-B31 are 0 */
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*SGL |= ((long) (f->exp << SGL_EXPSHIFT) << EXP_STORE);
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if (f->sign)
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*SGL |= CARRYBIT;
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/*
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* STORE MANTISSA
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*/
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put4(*SGL, (char *) &SGL);
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}
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}
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