1 /* @(#)s_nextafter.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 /* IEEE functions 14 * nexttoward(x,y) 15 * return the next machine floating-point number of x in the 16 * direction toward y. 17 * Special cases: 18 */ 19 20 #include <float.h> 21 #include <openlibm.h> 22 23 #include "math_private.h" 24 25 double 26 nexttoward(double x, long double y) 27 { 28 int32_t hx,ix; 29 int64_t hy,iy; 30 u_int32_t lx; 31 u_int64_t ly; 32 33 EXTRACT_WORDS(hx,lx,x); 34 GET_LDOUBLE_WORDS64(hy,ly,y); 35 ix = hx&0x7fffffff; /* |x| */ 36 iy = hy&0x7fffffffffffffffLL; /* |y| */ 37 38 if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */ 39 ((iy>=0x7fff000000000000LL)&&((iy-0x7fff000000000000LL)|ly)!=0)) 40 /* y is nan */ 41 return x+y; 42 if((long double) x==y) return y; /* x=y, return y */ 43 if((ix|lx)==0) { /* x == 0 */ 44 volatile double u; 45 INSERT_WORDS(x,(u_int32_t)((hy>>32)&0x80000000),1);/* return +-minsub */ 46 u = x; 47 u = u * u; /* raise underflow flag */ 48 return x; 49 } 50 if(hx>=0) { /* x > 0 */ 51 if (hy<0||(ix>>20)>(iy>>48)-0x3c00 52 || ((ix>>20)==(iy>>48)-0x3c00 53 && (((((int64_t)hx)<<28)|(lx>>4))>(hy&0x0000ffffffffffffLL) 54 || (((((int64_t)hx)<<28)|(lx>>4))==(hy&0x0000ffffffffffffLL) 55 && (lx&0xf)>(ly>>60))))) { /* x > y, x -= ulp */ 56 if(lx==0) hx -= 1; 57 lx -= 1; 58 } else { /* x < y, x += ulp */ 59 lx += 1; 60 if(lx==0) hx += 1; 61 } 62 } else { /* x < 0 */ 63 if (hy>=0||(ix>>20)>(iy>>48)-0x3c00 64 || ((ix>>20)==(iy>>48)-0x3c00 65 && (((((int64_t)hx)<<28)|(lx>>4))>(hy&0x0000ffffffffffffLL) 66 || (((((int64_t)hx)<<28)|(lx>>4))==(hy&0x0000ffffffffffffLL) 67 && (lx&0xf)>(ly>>60))))) { /* x < y, x -= ulp */ 68 if(lx==0) hx -= 1; 69 lx -= 1; 70 } else { /* x > y, x += ulp */ 71 lx += 1; 72 if(lx==0) hx += 1; 73 } 74 } 75 hy = hx&0x7ff00000; 76 if(hy>=0x7ff00000) { 77 x = x+x; /* overflow */ 78 return x; 79 } 80 if(hy<0x00100000) { 81 volatile double u = x*x; /* underflow */ 82 } 83 INSERT_WORDS(x,hx,lx); 84 return x; 85 } 86