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gohigh
185
Book-Lite/linux-0.12/kernel/math/convert.c
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185
Book-Lite/linux-0.12/kernel/math/convert.c
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/*
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* linux/kernel/math/convert.c
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*
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* (C) 1991 Linus Torvalds
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*/
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#include <linux/math_emu.h>
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/*
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* NOTE!!! There is some "non-obvious" optimisations in the temp_to_long
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* and temp_to_short conversion routines: don't touch them if you don't
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* know what's going on. They are the adding of one in the rounding: the
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* overflow bit is also used for adding one into the exponent. Thus it
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* looks like the overflow would be incorrectly handled, but due to the
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* way the IEEE numbers work, things are correct.
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*
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* There is no checking for total overflow in the conversions, though (ie
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* if the temp-real number simply won't fit in a short- or long-real.)
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*/
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void short_to_temp(const short_real * a, temp_real * b)
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{
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if (!(*a & 0x7fffffff)) {
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b->a = b->b = 0;
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if (*a)
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b->exponent = 0x8000;
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else
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b->exponent = 0;
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return;
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}
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b->exponent = ((*a>>23) & 0xff)-127+16383;
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if (*a<0)
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b->exponent |= 0x8000;
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b->b = (*a<<8) | 0x80000000;
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b->a = 0;
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}
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void long_to_temp(const long_real * a, temp_real * b)
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{
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if (!a->a && !(a->b & 0x7fffffff)) {
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b->a = b->b = 0;
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if (a->b)
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b->exponent = 0x8000;
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else
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b->exponent = 0;
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return;
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}
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b->exponent = ((a->b >> 20) & 0x7ff)-1023+16383;
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if (a->b<0)
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b->exponent |= 0x8000;
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b->b = 0x80000000 | (a->b<<11) | (((unsigned long)a->a)>>21);
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b->a = a->a<<11;
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}
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void temp_to_short(const temp_real * a, short_real * b)
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{
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if (!(a->exponent & 0x7fff)) {
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*b = (a->exponent)?0x80000000:0;
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return;
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}
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*b = ((((long) a->exponent)-16383+127) << 23) & 0x7f800000;
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if (a->exponent < 0)
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*b |= 0x80000000;
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*b |= (a->b >> 8) & 0x007fffff;
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switch (ROUNDING) {
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case ROUND_NEAREST:
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if ((a->b & 0xff) > 0x80)
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++*b;
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break;
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case ROUND_DOWN:
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if ((a->exponent & 0x8000) && (a->b & 0xff))
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++*b;
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break;
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case ROUND_UP:
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if (!(a->exponent & 0x8000) && (a->b & 0xff))
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++*b;
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break;
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}
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}
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void temp_to_long(const temp_real * a, long_real * b)
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{
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if (!(a->exponent & 0x7fff)) {
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b->a = 0;
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b->b = (a->exponent)?0x80000000:0;
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return;
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}
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b->b = (((0x7fff & (long) a->exponent)-16383+1023) << 20) & 0x7ff00000;
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if (a->exponent < 0)
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b->b |= 0x80000000;
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b->b |= (a->b >> 11) & 0x000fffff;
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b->a = a->b << 21;
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b->a |= (a->a >> 11) & 0x001fffff;
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switch (ROUNDING) {
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case ROUND_NEAREST:
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if ((a->a & 0x7ff) > 0x400)
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__asm__("addl $1,%0 ; adcl $0,%1"
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:"=r" (b->a),"=r" (b->b)
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:"0" (b->a),"1" (b->b));
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break;
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case ROUND_DOWN:
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if ((a->exponent & 0x8000) && (a->b & 0xff))
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__asm__("addl $1,%0 ; adcl $0,%1"
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:"=r" (b->a),"=r" (b->b)
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:"0" (b->a),"1" (b->b));
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break;
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case ROUND_UP:
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if (!(a->exponent & 0x8000) && (a->b & 0xff))
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__asm__("addl $1,%0 ; adcl $0,%1"
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:"=r" (b->a),"=r" (b->b)
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:"0" (b->a),"1" (b->b));
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break;
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}
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}
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void real_to_int(const temp_real * a, temp_int * b)
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{
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int shift = 16383 + 63 - (a->exponent & 0x7fff);
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unsigned long underflow;
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b->a = b->b = underflow = 0;
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b->sign = (a->exponent < 0);
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if (shift < 0) {
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set_OE();
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return;
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}
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if (shift < 32) {
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b->b = a->b; b->a = a->a;
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} else if (shift < 64) {
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b->a = a->b; underflow = a->a;
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shift -= 32;
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} else if (shift < 96) {
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underflow = a->b;
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shift -= 64;
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} else
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return;
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__asm__("shrdl %2,%1,%0"
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:"=r" (underflow),"=r" (b->a)
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:"c" ((char) shift),"0" (underflow),"1" (b->a));
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__asm__("shrdl %2,%1,%0"
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:"=r" (b->a),"=r" (b->b)
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:"c" ((char) shift),"0" (b->a),"1" (b->b));
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__asm__("shrl %1,%0"
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:"=r" (b->b)
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:"c" ((char) shift),"0" (b->b));
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switch (ROUNDING) {
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case ROUND_NEAREST:
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__asm__("addl %4,%5 ; adcl $0,%0 ; adcl $0,%1"
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:"=r" (b->a),"=r" (b->b)
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:"0" (b->a),"1" (b->b)
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,"r" (0x7fffffff + (b->a & 1))
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,"m" (*&underflow));
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break;
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case ROUND_UP:
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if (!b->sign && underflow)
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__asm__("addl $1,%0 ; adcl $0,%1"
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:"=r" (b->a),"=r" (b->b)
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:"0" (b->a),"1" (b->b));
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break;
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case ROUND_DOWN:
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if (b->sign && underflow)
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__asm__("addl $1,%0 ; adcl $0,%1"
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:"=r" (b->a),"=r" (b->b)
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:"0" (b->a),"1" (b->b));
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break;
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}
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}
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void int_to_real(const temp_int * a, temp_real * b)
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{
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b->a = a->a;
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b->b = a->b;
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if (b->a || b->b)
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b->exponent = 16383 + 63 + (a->sign? 0x8000:0);
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else {
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b->exponent = 0;
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return;
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}
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while (b->b >= 0) {
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b->exponent--;
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__asm__("addl %0,%0 ; adcl %1,%1"
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:"=r" (b->a),"=r" (b->b)
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:"0" (b->a),"1" (b->b));
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}
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}
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