1 /* 2 * ==================================================== 3 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 4 * 5 * Developed at SunPro, a Sun Microsystems, Inc. business. 6 * Permission to use, copy, modify, and distribute this 7 * software is freely granted, provided that this notice 8 * is preserved. 9 * ==================================================== 10 */ 11 12 #include <sys/cdefs.h> 13 /* 14 * We assume that a long double has a 15-bit exponent. On systems 15 * where long double is the same as double, nexttoward() is an alias 16 * for nextafter(), so we don't use this routine. 17 */ 18 19 #include <float.h> 20 21 #include "fpmath.h" 22 #include "math.h" 23 #include "math_private.h" 24 25 #if LDBL_MAX_EXP != 0x4000 26 #error "Unsupported long double format" 27 #endif 28 29 double 30 nexttoward(double x, long double y) 31 { 32 union IEEEl2bits uy; 33 volatile double t; 34 int32_t hx,ix; 35 u_int32_t lx; 36 37 EXTRACT_WORDS(hx,lx,x); 38 ix = hx&0x7fffffff; /* |x| */ 39 uy.e = y; 40 41 if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || 42 (uy.bits.exp == 0x7fff && 43 ((uy.bits.manh&~LDBL_NBIT)|uy.bits.manl) != 0)) 44 return x+y; /* x or y is nan */ 45 if(x==y) return (double)y; /* x=y, return y */ 46 if(x==0.0) { 47 INSERT_WORDS(x,uy.bits.sign<<31,1); /* return +-minsubnormal */ 48 t = x*x; 49 if(t==x) return t; else return x; /* raise underflow flag */ 50 } 51 if(hx>0.0 ^ x < y) { /* x -= ulp */ 52 if(lx==0) hx -= 1; 53 lx -= 1; 54 } else { /* x += ulp */ 55 lx += 1; 56 if(lx==0) hx += 1; 57 } 58 ix = hx&0x7ff00000; 59 if(ix>=0x7ff00000) return x+x; /* overflow */ 60 if(ix<0x00100000) { /* underflow */ 61 t = x*x; 62 if(t!=x) { /* raise underflow flag */ 63 INSERT_WORDS(x,hx,lx); 64 return x; 65 } 66 } 67 INSERT_WORDS(x,hx,lx); 68 return x; 69 } 70