math: raise invalid flag in ilogb*.c on +-0, +-inf and nan

[musl] / src / math / scalbnl.c

diff --git a/src/math/scalbnl.c b/src/math/scalbnl.c
index 0ed5b7f..c605b8d 100644 (file)
--- a/src/math/scalbnl.c
+++ b/src/math/scalbnl.c
@@ -1,21 +1,3 @@
-/* origin: FreeBSD /usr/src/lib/msun/src/s_scalbnl.c */
-/*
- * ====================================================
- * 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
- * is preserved.
- * ====================================================
- */
-/*
- * scalbnl (long double x, int n)
- * scalbnl(x,n) returns x* 2**n  computed by  exponent
- * manipulation rather than by actually performing an
- * exponentiation or a multiplication.
- */
-
 #include "libm.h"
 
 #if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
@@ -24,40 +6,31 @@ long double scalbnl(long double x, int n)
        return scalbn(x, n);
 }
 #elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
-static const long double
-huge = 0x1p16000L,
-tiny = 0x1p-16000L;
-
 long double scalbnl(long double x, int n)
 {
-       union IEEEl2bits u;
-       int k;
+       union IEEEl2bits scale;
 
-       u.e = x;
-       k = u.bits.exp;                    /* extract exponent */
-       if (k == 0) {                      /* 0 or subnormal x */
-               if ((u.bits.manh|u.bits.manl) == 0)  /* +-0 */
-                       return x;
-               u.e *= 0x1p128;
-               k = u.bits.exp - 128;
-               if (n < -50000)
-                       return tiny*x;  /*underflow*/
-       }
-       if (k == 0x7fff)                   /* NaN or Inf */
-               return x + x;
-       k = k + n;
-       if (k >= 0x7fff)
-               return huge*copysignl(huge, x);  /* overflow  */
-       if (k > 0) {                       /* normal result */
-               u.bits.exp = k;
-               return u.e;
+       if (n > 16383) {
+               x *= 0x1p16383L;
+               n -= 16383;
+               if (n > 16383) {
+                       x *= 0x1p16383L;
+                       n -= 16383;
+                       if (n > 16383)
+                               return x * 0x1p16383L;
+               }
+       } else if (n < -16382) {
+               x *= 0x1p-16382L;
+               n += 16382;
+               if (n < -16382) {
+                       x *= 0x1p-16382L;
+                       n += 16382;
+                       if (n < -16382)
+                               return x * 0x1p-16382L;
+               }
        }
-       if (k <= -128)
-               if (n > 50000)  /* in case integer overflow in n+k */
-                       return huge*copysign(huge, x);  /*overflow*/
-               return tiny*copysign(tiny, x);  /*underflow*/
-       k += 128;                          /* subnormal result */
-       u.bits.exp = k;
-       return u.e*0x1p-128;
+       scale.e = 1.0;
+       scale.bits.exp = 0x3fff + n;
+       return x * scale.e;
 }
 #endif