1 files changed, 164 insertions, 0 deletions
diff --git a/libm/ldouble/powil.c b/libm/ldouble/powil.c
new file mode 100644
index 000000000..d36c7854e
--- /dev/null
+++ b/libm/ldouble/powil.c
@@ -0,0 +1,164 @@
+/*							powil.c
+ *
+ *	Real raised to integer power, long double precision
+ *
+ *
+ *
+ * SYNOPSIS:
+ *
+ * long double x, y, powil();
+ * int n;
+ *
+ * y = powil( x, n );
+ *
+ *
+ *
+ * DESCRIPTION:
+ *
+ * Returns argument x raised to the nth power.
+ * The routine efficiently decomposes n as a sum of powers of
+ * two. The desired power is a product of two-to-the-kth
+ * powers of x.  Thus to compute the 32767 power of x requires
+ * 28 multiplications instead of 32767 multiplications.
+ *
+ *
+ *
+ * ACCURACY:
+ *
+ *
+ *                      Relative error:
+ * arithmetic   x domain   n domain  # trials      peak         rms
+ *    IEEE     .001,1000  -1022,1023  50000       4.3e-17     7.8e-18
+ *    IEEE        1,2     -1022,1023  20000       3.9e-17     7.6e-18
+ *    IEEE     .99,1.01     0,8700    10000       3.6e-16     7.2e-17
+ *
+ * Returns MAXNUM on overflow, zero on underflow.
+ *
+ */
+
+/*							powil.c	*/
+
+/*
+Cephes Math Library Release 2.2:  December, 1990
+Copyright 1984, 1990 by Stephen L. Moshier
+Direct inquiries to 30 Frost Street, Cambridge, MA 02140
+*/
+
+#include <math.h>
+extern long double MAXNUML, MAXLOGL, MINLOGL;
+extern long double LOGE2L;
+#ifdef ANSIPROT
+extern long double frexpl ( long double, int * );
+#else
+long double frexpl();
+#endif
+
+long double powil( x, nn )
+long double x;
+int nn;
+{
+long double w, y;
+long double s;
+int n, e, sign, asign, lx;
+
+if( x == 0.0L )
+	{
+	if( nn == 0 )
+		return( 1.0L );
+	else if( nn < 0 )
+		return( MAXNUML );
+	else
+		return( 0.0L );
+	}
+
+if( nn == 0 )
+	return( 1.0L );
+
+
+if( x < 0.0L )
+	{
+	asign = -1;
+	x = -x;
+	}
+else
+	asign = 0;
+
+
+if( nn < 0 )
+	{
+	sign = -1;
+	n = -nn;
+	}
+else
+	{
+	sign = 1;
+	n = nn;
+	}
+
+/* Overflow detection */
+
+/* Calculate approximate logarithm of answer */
+s = x;
+s = frexpl( s, &lx );
+e = (lx - 1)*n;
+if( (e == 0) || (e > 64) || (e < -64) )
+	{
+	s = (s - 7.0710678118654752e-1L) / (s +  7.0710678118654752e-1L);
+	s = (2.9142135623730950L * s - 0.5L + lx) * nn * LOGE2L;
+	}
+else
+	{
+	s = LOGE2L * e;
+	}
+
+if( s > MAXLOGL )
+	{
+	mtherr( "powil", OVERFLOW );
+	y = MAXNUML;
+	goto done;
+	}
+
+if( s < MINLOGL )
+	{
+	mtherr( "powil", UNDERFLOW );
+	return(0.0L);
+	}
+/* Handle tiny denormal answer, but with less accuracy
+ * since roundoff error in 1.0/x will be amplified.
+ * The precise demarcation should be the gradual underflow threshold.
+ */
+if( s < (-MAXLOGL+2.0L) )
+	{
+	x = 1.0L/x;
+	sign = -sign;
+	}
+
+/* First bit of the power */
+if( n & 1 )
+	y = x;
+		
+else
+	{
+	y = 1.0L;
+	asign = 0;
+	}
+
+w = x;
+n >>= 1;
+while( n )
+	{
+	w = w * w;	/* arg to the 2-to-the-kth power */
+	if( n & 1 )	/* if that bit is set, then include in product */
+		y *= w;
+	n >>= 1;
+	}
+
+
+done:
+
+if( asign )
+	y = -y; /* odd power of negative number */
+if( sign < 0 )
+	y = 1.0L/y;
+return(y);
+}