kernel/math/div.c

/* */
This source file includes following definitions.
shift_left
shift_right
try_sub
div64
fdiv
   1 /*
   2  * linux/kernel/math/div.c
   3  *
   4  * Copyright (C) 1991, 1992 Linus Torvalds
   5  */
   6 
   7 /*
   8  * temporary real division routine.
   9  */
  10 
  11 #include <linux/math_emu.h>
  12 
  13 static void shift_left(int * c)
     /*  */
  14 {
  15         __asm__ __volatile__("movl (%0),%%eax ; addl %%eax,(%0)\n\t"
  16                 "movl 4(%0),%%eax ; adcl %%eax,4(%0)\n\t"
  17                 "movl 8(%0),%%eax ; adcl %%eax,8(%0)\n\t"
  18                 "movl 12(%0),%%eax ; adcl %%eax,12(%0)"
  19                 ::"r" ((long) c):"ax");
  20 }
  21 
  22 static void shift_right(int * c)
     /*  */
  23 {
  24         __asm__("shrl $1,12(%0) ; rcrl $1,8(%0) ; rcrl $1,4(%0) ; rcrl $1,(%0)"
  25                 ::"r" ((long) c));
  26 }
  27 
  28 static int try_sub(int * a, int * b)
     /*  */
  29 {
  30         char ok;
  31 
  32         __asm__ __volatile__("movl (%1),%%eax ; subl %%eax,(%2)\n\t"
  33                 "movl 4(%1),%%eax ; sbbl %%eax,4(%2)\n\t"
  34                 "movl 8(%1),%%eax ; sbbl %%eax,8(%2)\n\t"
  35                 "movl 12(%1),%%eax ; sbbl %%eax,12(%2)\n\t"
  36                 "setae %%al":"=a" (ok):"c" ((long) a),"d" ((long) b));
  37         return ok;
  38 }
  39 
  40 static void div64(int * a, int * b, int * c)
     /*  */
  41 {
  42         int tmp[4];
  43         int i;
  44         unsigned int mask = 0;
  45 
  46         c += 4;
  47         for (i = 0 ; i<64 ; i++) {
  48                 if (!(mask >>= 1)) {
  49                         c--;
  50                         mask = 0x80000000;
  51                 }
  52                 tmp[0] = a[0]; tmp[1] = a[1];
  53                 tmp[2] = a[2]; tmp[3] = a[3];
  54                 if (try_sub(b,tmp)) {
  55                         *c |= mask;
  56                         a[0] = tmp[0]; a[1] = tmp[1];
  57                         a[2] = tmp[2]; a[3] = tmp[3];
  58                 }
  59                 shift_right(b);
  60         }
  61 }
  62 
  63 void fdiv(const temp_real * src1, const temp_real * src2, temp_real * result)
     /*  */
  64 {
  65         int i,sign;
  66         int a[4],b[4],tmp[4] = {0,0,0,0};
  67 
  68         sign = (src1->exponent ^ src2->exponent) & 0x8000;
  69         if (!(src2->a || src2->b)) {
  70                 set_ZE();
  71                 return;
  72         }
  73         i = (src1->exponent & 0x7fff) - (src2->exponent & 0x7fff) + 16383;
  74         if (i<0) {
  75                 set_UE();
  76                 result->exponent = sign;
  77                 result->a = result->b = 0;
  78                 return;
  79         }
  80         a[0] = a[1] = 0;
  81         a[2] = src1->a;
  82         a[3] = src1->b;
  83         b[0] = b[1] = 0;
  84         b[2] = src2->a;
  85         b[3] = src2->b;
  86         while (b[3] >= 0) {
  87                 i++;
  88                 shift_left(b);
  89         }
  90         div64(a,b,tmp);
  91         if (tmp[0] || tmp[1] || tmp[2] || tmp[3]) {
  92                 while (i && tmp[3] >= 0) {
  93                         i--;
  94                         shift_left(tmp);
  95                 }
  96                 if (tmp[3] >= 0)
  97                         set_DE();
  98         } else
  99                 i = 0;
 100         if (i>0x7fff) {
 101                 set_OE();
 102                 return;
 103         }
 104         if (tmp[0] || tmp[1])
 105                 set_PE();
 106         result->exponent = i | sign;
 107         result->a = tmp[2];
 108         result->b = tmp[3];
 109 }
/* */
root/kernel/math/div.c

DEFINITIONS
