?? add.c
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/* * linux/kernel/math/add.c * * (C) 1991 Linus Torvalds *//* * temporary real addition routine. * * NOTE! These aren't exact: they are only 62 bits wide, and don't do * correct rounding. Fast hack. The reason is that we shift right the * values by two, in order not to have overflow (1 bit), and to be able * to move the sign into the mantissa (1 bit). Much simpler algorithms, * and 62 bits (61 really - no rounding) accuracy is usually enough. The * only time you should notice anything weird is when adding 64-bit * integers together. When using doubles (52 bits accuracy), the * 61-bit accuracy never shows at all. */#include <linux/math_emu.h>#define NEGINT(a) \__asm__("notl %0 ; notl %1 ; addl $1,%0 ; adcl $0,%1" \ :"=r" (a->a),"=r" (a->b) \ :"0" (a->a),"1" (a->b))static void signify(temp_real * a){ a->exponent += 2; __asm__("shrdl $2,%1,%0 ; shrl $2,%1" :"=r" (a->a),"=r" (a->b) :"0" (a->a),"1" (a->b)); if (a->exponent < 0) NEGINT(a); a->exponent &= 0x7fff;}static void unsignify(temp_real * a){ if (!(a->a || a->b)) { a->exponent = 0; return; } a->exponent &= 0x7fff; if (a->b < 0) { NEGINT(a); a->exponent |= 0x8000; } while (a->b >= 0) { a->exponent--; __asm__("addl %0,%0 ; adcl %1,%1" :"=r" (a->a),"=r" (a->b) :"0" (a->a),"1" (a->b)); }}void fadd(const temp_real * src1, const temp_real * src2, temp_real * result){ temp_real a,b; int x1,x2,shift; x1 = src1->exponent & 0x7fff; x2 = src2->exponent & 0x7fff; if (x1 > x2) { a = *src1; b = *src2; shift = x1-x2; } else { a = *src2; b = *src1; shift = x2-x1; } if (shift >= 64) { *result = a; return; } if (shift >= 32) { b.a = b.b; b.b = 0; shift -= 32; } __asm__("shrdl %4,%1,%0 ; shrl %4,%1" :"=r" (b.a),"=r" (b.b) :"0" (b.a),"1" (b.b),"c" ((char) shift)); signify(&a); signify(&b); __asm__("addl %4,%0 ; adcl %5,%1" :"=r" (a.a),"=r" (a.b) :"0" (a.a),"1" (a.b),"g" (b.a),"g" (b.b)); unsignify(&a); *result = a;}
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