LINUX 内核

				/*				 * linux/kernel/math/div.c				 *				 * (C) 1991 Linus Torvalds				 */								/*				 * temporary real division routine.				 */								#include 								static void shift_left(int * c)				{					__asm__ __volatile__("movl (%0),%%eax ; addl %%eax,(%0)\n\t"						"movl 4(%0),%%eax ; adcl %%eax,4(%0)\n\t"						"movl 8(%0),%%eax ; adcl %%eax,8(%0)\n\t"						"movl 12(%0),%%eax ; adcl %%eax,12(%0)"						::"r" ((long) c):"ax");				}								static void shift_right(int * c)				{					__asm__("shrl $1,12(%0) ; rcrl $1,8(%0) ; rcrl $1,4(%0) ; rcrl $1,(%0)"						::"r" ((long) c));				}								static int try_sub(int * a, int * b)				{					char ok;									__asm__ __volatile__("movl (%1),%%eax ; subl %%eax,(%2)\n\t"						"movl 4(%1),%%eax ; sbbl %%eax,4(%2)\n\t"						"movl 8(%1),%%eax ; sbbl %%eax,8(%2)\n\t"						"movl 12(%1),%%eax ; sbbl %%eax,12(%2)\n\t"						"setae %%al":"=a" (ok):"c" ((long) a),"d" ((long) b));					return ok;				}								static void div64(int * a, int * b, int * c)				{					int tmp[4];					int i;					unsigned int mask = 0;									c += 4;					for (i = 0 ; i						if (!(mask >>= 1)) {							c--;							mask = 0x80000000;						}						tmp[0] = a[0]; tmp[1] = a[1];						tmp[2] = a[2]; tmp[3] = a[3];						if (try_sub(b,tmp)) {							*c |= mask;							a[0] = tmp[0]; a[1] = tmp[1];							a[2] = tmp[2]; a[3] = tmp[3];						}						shift_right(b);					}				}								void fdiv(const temp_real * src1, const temp_real * src2, temp_real * result)				{					int i,sign;					int a[4],b[4],tmp[4] = {0,0,0,0};									sign = (src1->exponent ^ src2->exponent) & 0x8000;					if (!(src2->a || src2->b)) {						set_ZE();						return;					}					i = (src1->exponent & 0x7fff) - (src2->exponent & 0x7fff) + 16383;					if (i						set_UE();						result->exponent = sign;						result->a = result->b = 0;						return;					}					a[0] = a[1] = 0;					a[2] = src1->a;					a[3] = src1->b;					b[0] = b[1] = 0;					b[2] = src2->a;					b[3] = src2->b;					while (b[3] >= 0) {						i++;						shift_left(b);					}					div64(a,b,tmp);					if (tmp[0] || tmp[1] || tmp[2] || tmp[3]) {						while (i && tmp[3] >= 0) {							i--;							shift_left(tmp);						}						if (tmp[3] >= 0)							set_DE();					} else						i = 0;					if (i>0x7fff) {						set_OE();						return;					}					if (tmp[0] || tmp[1])						set_PE();					result->exponent = i | sign;					result->a = tmp[2];					result->b = tmp[3];				}