1*05a0b428SJohn Marino /* @(#)s_ilogb.c 5.1 93/09/24 */ 2*05a0b428SJohn Marino /* 3*05a0b428SJohn Marino * ==================================================== 4*05a0b428SJohn Marino * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 5*05a0b428SJohn Marino * 6*05a0b428SJohn Marino * Developed at SunPro, a Sun Microsystems, Inc. business. 7*05a0b428SJohn Marino * Permission to use, copy, modify, and distribute this 8*05a0b428SJohn Marino * software is freely granted, provided that this notice 9*05a0b428SJohn Marino * is preserved. 10*05a0b428SJohn Marino * ==================================================== 11*05a0b428SJohn Marino */ 12*05a0b428SJohn Marino 13*05a0b428SJohn Marino /* ilogb(double x) 14*05a0b428SJohn Marino * return the binary exponent of non-zero x 15*05a0b428SJohn Marino * ilogb(0) = 0x80000001 16*05a0b428SJohn Marino * ilogb(inf/NaN) = 0x7fffffff (no signal is raised) 17*05a0b428SJohn Marino */ 18*05a0b428SJohn Marino 19*05a0b428SJohn Marino #include <float.h> 20*05a0b428SJohn Marino #include <math.h> 21*05a0b428SJohn Marino 22*05a0b428SJohn Marino #include "math_private.h" 23*05a0b428SJohn Marino 24*05a0b428SJohn Marino int 25*05a0b428SJohn Marino ilogb(double x) 26*05a0b428SJohn Marino { 27*05a0b428SJohn Marino int32_t hx,lx,ix; 28*05a0b428SJohn Marino 29*05a0b428SJohn Marino GET_HIGH_WORD(hx,x); 30*05a0b428SJohn Marino hx &= 0x7fffffff; 31*05a0b428SJohn Marino if(hx<0x00100000) { 32*05a0b428SJohn Marino GET_LOW_WORD(lx,x); 33*05a0b428SJohn Marino if((hx|lx)==0) 34*05a0b428SJohn Marino return 0x80000001; /* ilogb(0) = 0x80000001 */ 35*05a0b428SJohn Marino else /* subnormal x */ 36*05a0b428SJohn Marino if(hx==0) { 37*05a0b428SJohn Marino for (ix = -1043; lx>0; lx<<=1) ix -=1; 38*05a0b428SJohn Marino } else { 39*05a0b428SJohn Marino for (ix = -1022,hx<<=11; hx>0; hx<<=1) ix -=1; 40*05a0b428SJohn Marino } 41*05a0b428SJohn Marino return ix; 42*05a0b428SJohn Marino } 43*05a0b428SJohn Marino else if (hx<0x7ff00000) return (hx>>20)-1023; 44*05a0b428SJohn Marino else return 0x7fffffff; 45*05a0b428SJohn Marino } 46*05a0b428SJohn Marino 47*05a0b428SJohn Marino #if LDBL_MANT_DIG == DBL_MANT_DIG 48*05a0b428SJohn Marino __strong_alias(ilogbl, ilogb); 49*05a0b428SJohn Marino #endif /* LDBL_MANT_DIG == DBL_MANT_DIG */ 50