dl-string.h: remove mips related guard

[uclinux-h8/uClibc.git] / libm / s_ilogb.c

diff --git a/libm/s_ilogb.c b/libm/s_ilogb.c
index ee81570..259ae7b 100644 (file)
--- a/libm/s_ilogb.c
+++ b/libm/s_ilogb.c
@@ -1,51 +1,57 @@
-/* @(#)s_ilogb.c 5.1 93/09/24 */
 /*
  * ====================================================
  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
  *
  * Developed at SunPro, a Sun Microsystems, Inc. business.
  * Permission to use, copy, modify, and distribute this
- * software is freely granted, provided that this notice 
+ * software is freely granted, provided that this notice
  * is preserved.
  * ====================================================
  */
 
-#if defined(LIBM_SCCS) && !defined(lint)
-static char rcsid[] = "$NetBSD: s_ilogb.c,v 1.9 1995/05/10 20:47:28 jtc Exp $";
-#endif
-
 /* ilogb(double x)
- * return the binary exponent of non-zero x
- * ilogb(0) = 0x80000001
- * ilogb(inf/NaN) = 0x7fffffff (no signal is raised)
+ * return the binary exponent of x
+ * ilogb(+-0) = FP_ILOGB0
+ * ilogb(+-inf) = INT_MAX
+ * ilogb(NaN) = FP_ILOGBNAN (no signal is raised)
  */
 
 #include "math.h"
 #include "math_private.h"
 
-#ifdef __STDC__
-       int ilogb(double x)
-#else
-       int ilogb(x)
-       double x;
-#endif
+int ilogb(double x)
 {
        int32_t hx,lx,ix;
 
-       GET_HIGH_WORD(hx,x);
+       GET_HIGH_WORD(hx, x);
        hx &= 0x7fffffff;
-       if(hx<0x00100000) {
-           GET_LOW_WORD(lx,x);
-           if((hx|lx)==0) 
-               return 0x80000001;      /* ilogb(0) = 0x80000001 */
-           else                        /* subnormal x */
-               if(hx==0) {
-                   for (ix = -1043; lx>0; lx<<=1) ix -=1;
-               } else {
-                   for (ix = -1022,hx<<=11; hx>0; hx<<=1) ix -=1;
+
+       if (hx < 0x00100000) {
+               GET_LOW_WORD(lx, x);
+               if ((hx|lx)==0)  /* +-0, ilogb(0) = FP_ILOGB0 */
+                       return FP_ILOGB0;
+               /* subnormal x */
+               ix = -1043;
+               if (hx != 0) {
+                       ix = -1022;
+                       lx = (hx << 11);
                }
-           return ix;
+               /* each leading zero mantissa bit makes exponent smaller */
+               for (; lx > 0; lx <<= 1)
+                       ix--;
+               return ix;
+       }
+
+       if (hx < 0x7ff00000) /* normal x */
+               return (hx>>20) - 1023;
+
+       if (FP_ILOGBNAN != (~0U >> 1)) {
+               GET_LOW_WORD(lx, x);
+               if (hx == 0x7ff00000 && lx == 0)  /* +-inf */
+                       return ~0U >> 1; /* = INT_MAX */
        }
-       else if (hx<0x7ff00000) return (hx>>20)-1023;
-       else return 0x7fffffff;
+
+       /* NAN. ilogb(NAN) = FP_ILOGBNAN */
+       return FP_ILOGBNAN;
 }
+libm_hidden_def(ilogb)