contrib/openbsd_libm/src/ld80/s_floorl.c

   1 /* @(#)s_floor.c 5.1 93/09/24 */
   2 /*
   3  * ====================================================
   4  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   5  *
   6  * Developed at SunPro, a Sun Microsystems, Inc. business.
   7  * Permission to use, copy, modify, and distribute this
   8  * software is freely granted, provided that this notice
   9  * is preserved.
  10  * ====================================================
  11  */
  12
  13 /*
  14  * floorl(x)
  15  * Return x rounded toward -inf to integral value
  16  * Method:
  17  *      Bit twiddling.
  18  * Exception:
  19  *      Inexact flag raised if x not equal to floor(x).
  20  */
  21
  22 #include <math.h>
  23
  24 #include "math_private.h"
  25
  26 static const long double huge = 1.0e4930L;
  27
  28 long double
  29 floorl(long double x)
  30 {
  31         int32_t i1,jj0;
  32         u_int32_t i,j,se,i0,sx;
  33         GET_LDOUBLE_WORDS(se,i0,i1,x);
  34         sx = (se>>15)&1;
  35         jj0 = (se&0x7fff)-0x3fff;
  36         if(jj0<31) {
  37             if(jj0<0) { /* raise inexact if x != 0 */
  38                 if(huge+x>0.0) {
  39                     if(sx==0)
  40                         return 0.0L;
  41                     else if(((se&0x7fff)|i0|i1)!=0)
  42                         return -1.0L;
  43                 }
  44             } else {
  45                 i = (0x7fffffff)>>jj0;
  46                 if(((i0&i)|i1)==0) return x; /* x is integral */
  47                 if(huge+x>0.0) {        /* raise inexact flag */
  48                     if(sx) {
  49                         if (jj0>0 && (i0+(0x80000000>>jj0))>i0)
  50                           i0 += (0x80000000)>>jj0;
  51                         else
  52                           {
  53                             i = 0x7fffffff;
  54                             ++se;
  55                           }
  56                     }
  57                     i0 &= (~i); i1=0;
  58                 }
  59             }
  60         } else if (jj0>62) {
  61             if(jj0==0x4000) return x+x; /* inf or NaN */
  62             else return x;              /* x is integral */
  63         } else {
  64             i = ((u_int32_t)(0xffffffff))>>(jj0-31);
  65             if((i1&i)==0) return x;     /* x is integral */
  66             if(huge+x>0.0) {            /* raise inexact flag */
  67                 if(sx) {
  68                     if(jj0==31) i0+=1;
  69                     else {
  70                         j = i1+(1<<(63-jj0));
  71                         if(j<i1) i0 +=1 ;       /* got a carry */
  72                         i1=j;
  73                     }
  74                 }
  75                 i1 &= (~i);
  76             }
  77         }
  78         SET_LDOUBLE_WORDS(x,se,i0,i1);
  79         return x;
  80 }