s_rintf.c revision 97413
1/* s_rintf.c -- float version of s_rint.c. 2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. 3 */ 4 5/* 6 * ==================================================== 7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 8 * 9 * Developed at SunPro, a Sun Microsystems, Inc. business. 10 * Permission to use, copy, modify, and distribute this 11 * software is freely granted, provided that this notice 12 * is preserved. 13 * ==================================================== 14 */ 15 16#ifndef lint 17static char rcsid[] = "$FreeBSD: head/lib/msun/src/s_rintf.c 97413 2002-05-28 18:15:04Z alfred $"; 18#endif 19 20#include "math.h" 21#include "math_private.h" 22 23/* 24 * TWO23 is double instead of float to avoid a bug in gcc. Without 25 * this, gcc thinks that TWO23[sx]+x and w-TWO23[sx] already have float 26 * precision and doesn't clip them to float precision when they are 27 * assigned and returned. 28 */ 29static const double 30TWO23[2]={ 31 8.3886080000e+06, /* 0x4b000000 */ 32 -8.3886080000e+06, /* 0xcb000000 */ 33}; 34 35float 36rintf(float x) 37{ 38 int32_t i0,j0,sx; 39 u_int32_t i,i1; 40 float w,t; 41 GET_FLOAT_WORD(i0,x); 42 sx = (i0>>31)&1; 43 j0 = ((i0>>23)&0xff)-0x7f; 44 if(j0<23) { 45 if(j0<0) { 46 if((i0&0x7fffffff)==0) return x; 47 i1 = (i0&0x07fffff); 48 i0 &= 0xfff00000; 49 i0 |= ((i1|-i1)>>9)&0x400000; 50 SET_FLOAT_WORD(x,i0); 51 w = TWO23[sx]+x; 52 t = w-TWO23[sx]; 53 GET_FLOAT_WORD(i0,t); 54 SET_FLOAT_WORD(t,(i0&0x7fffffff)|(sx<<31)); 55 return t; 56 } else { 57 i = (0x007fffff)>>j0; 58 if((i0&i)==0) return x; /* x is integral */ 59 i>>=1; 60 if((i0&i)!=0) i0 = (i0&(~i))|((0x100000)>>j0); 61 } 62 } else { 63 if(j0==0x80) return x+x; /* inf or NaN */ 64 else return x; /* x is integral */ 65 } 66 SET_FLOAT_WORD(x,i0); 67 w = TWO23[sx]+x; 68 return w-TWO23[sx]; 69} 70