auto import from //depot/cupcake/@135843
diff --git a/libm/src/s_scalbn.c b/libm/src/s_scalbn.c
new file mode 100644
index 0000000..6218c11
--- /dev/null
+++ b/libm/src/s_scalbn.c
@@ -0,0 +1,79 @@
+/* @(#)s_scalbn.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
+ * is preserved.
+ * ====================================================
+ */
+
+#ifndef lint
+static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_scalbn.c,v 1.11 2005/03/07 21:27:37 das Exp $";
+#endif
+
+/*
+ * scalbn (double x, int n)
+ * scalbn(x,n) returns x* 2**n computed by exponent
+ * manipulation rather than by actually performing an
+ * exponentiation or a multiplication.
+ */
+
+#include <sys/cdefs.h>
+#include <float.h>
+
+#include "math.h"
+#include "math_private.h"
+
+static const double
+two54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
+twom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
+huge = 1.0e+300,
+tiny = 1.0e-300;
+
+double
+scalbn (double x, int n)
+{
+ int32_t k,hx,lx;
+ EXTRACT_WORDS(hx,lx,x);
+ k = (hx&0x7ff00000)>>20; /* extract exponent */
+ if (k==0) { /* 0 or subnormal x */
+ if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */
+ x *= two54;
+ GET_HIGH_WORD(hx,x);
+ k = ((hx&0x7ff00000)>>20) - 54;
+ if (n< -50000) return tiny*x; /*underflow*/
+ }
+ if (k==0x7ff) return x+x; /* NaN or Inf */
+ k = k+n;
+ if (k > 0x7fe) return huge*copysign(huge,x); /* overflow */
+ if (k > 0) /* normal result */
+ {SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20)); return x;}
+ if (k <= -54)
+ if (n > 50000) /* in case integer overflow in n+k */
+ return huge*copysign(huge,x); /*overflow*/
+ else return tiny*copysign(tiny,x); /*underflow*/
+ k += 54; /* subnormal result */
+ SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20));
+ return x*twom54;
+}
+
+// this is normally in FreeBSD's libc.
+double
+ldexp (double x, int n)
+{
+ return scalbn(x,n);
+}
+
+#if (LDBL_MANT_DIG == 53) //XXX: brian FIXME __weak_reference doesn work
+long double ldexpl (long double x, int n) {
+ return scalbn((double)x,n);
+}
+long double scalbnl (long double x, int n) {
+ return scalbn((double)x,n);
+}
+__weak_reference(scalbn, ldexpl);
+__weak_reference(scalbn, scalbnl);
+#endif