first commit of the new libm!

[musl] / src / math / scalbnl.c

diff --git a/src/math/scalbnl.c b/src/math/scalbnl.c
new file mode 100644 (file)
index 0000000..0ed5b7f
--- /dev/null
+++ b/src/math/scalbnl.c
@@ -0,0 +1,63 @@
+/* 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
+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;
+
+       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 (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;
+}
+#endif