70 lines
1.8 KiB
C
70 lines
1.8 KiB
C
#define BIAS80 16383
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#define BIAS64 1023
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typedef struct {
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int16_t begin;
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union {
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double d;
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uint64_t ll;
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} eind;
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} x87_conv_t;
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static __inline double
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x87_from80(x87_conv_t *test)
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{
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int64_t exp64;
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int64_t blah;
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int64_t exp64final;
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int64_t mant64;
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int64_t sign;
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exp64 = (((test->begin & 0x7fff) - BIAS80));
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blah = ((exp64 > 0) ? exp64 : -exp64) & 0x3ff;
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exp64final = ((exp64 > 0) ? blah : -blah) + BIAS64;
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mant64 = (test->eind.ll >> 11) & (0xfffffffffffffLL);
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sign = (test->begin & 0x8000) ? 1 : 0;
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if ((test->begin & 0x7fff) == 0x7fff)
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exp64final = 0x7ff;
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if ((test->begin & 0x7fff) == 0)
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exp64final = 0;
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if (test->eind.ll & 0x400)
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mant64++;
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test->eind.ll = (sign << 63) | (exp64final << 52) | mant64;
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return test->eind.d;
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}
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static __inline void
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x87_to80(double d, x87_conv_t *test)
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{
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int64_t sign80;
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int64_t exp80;
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int64_t exp80final;
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int64_t mant80;
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int64_t mant80final;
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test->eind.d = d;
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sign80 = (test->eind.ll & (0x8000000000000000LL)) ? 1 : 0;
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exp80 = test->eind.ll & (0x7ff0000000000000LL);
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exp80final = (exp80 >> 52);
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mant80 = test->eind.ll & (0x000fffffffffffffLL);
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mant80final = (mant80 << 11);
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if (exp80final == 0x7ff) /*Infinity / Nan*/
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{
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exp80final = 0x7fff;
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mant80final |= (0x8000000000000000LL);
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} else if (d != 0) { /* Zero is a special case */
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/* Elvira wants the 8 and tcalc doesn't */
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mant80final |= (0x8000000000000000LL);
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/* Ca-cyber doesn't like this when result is zero. */
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exp80final += (BIAS80 - BIAS64);
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}
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test->begin = (((int16_t) sign80) << 15) | (int16_t) exp80final;
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test->eind.ll = mant80final;
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}
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