Index: uspace/lib/math/generic/scalbn.c
===================================================================
--- uspace/lib/math/generic/scalbn.c	(revision 19520ba91e8305ff31992c5031c3381225f0b5a3)
+++ uspace/lib/math/generic/scalbn.c	(revision f250c5ad6a76a78db608d678ea270ea17a01cbe0)
@@ -18,40 +18,46 @@
 #include <stdint.h>
 
+#include "internal.h"
 
-/* scalbn(x,n) returns x* 2**n  computed by  exponent
+/*
+ * 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.
  */
 
-double scalbn(double x, int n)
+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)
 {
-	union {double f; uint64_t i;} u;
-	double_t y = x;
-
-	if (n > 1023) {
-		y *= 0x1p1023;
- 		n -= 1023;
-		if (n > 1023) {
-			y *= 0x1p1023;
-			n -= 1023;
-			if (n > 1023)
-				n = 1023;
-		}
-	} else if (n < -1022) {
-        /* make sure final n < -53 to avoid double
-           rounding in the subnormal range */
-		y *= 0x1p-1022 * 0x1p53;
-		n += 1022 - 53;
-		if (n < -1022) {
-			y *= 0x1p-1022 * 0x1p53;
-			n += 1022 - 53;
-			if (n < -1022)
-				n = -1022;
-		}
+	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*/
 	}
-	u.i = (uint64_t)(0x3ff+n)<<52;
-	x = y * u.f;
-
-	return x;
+        k += 54;				/* subnormal result */
+	SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20));
+        return x*twom54;
 }