add LCC - a better C-Compiler for WEGA

WEGA/contrib/lcc/lib/libc/port/gen/ldexp.c

@@ -0,0 +1,36 @@
+/*
+ * ldexp(value, exp) returns the quantity value * 2 ** exp.
+ * In the event of overflow, on UNIX a floating-point exception is signalled.
+ * In the event of underflow, zero is returned.
+ *
+ */
+
+#include <nan.h>
+#include <values.h>
+/* Largest long int power of 2 */
+#define MAXSHIFT	(BITSPERBYTE * sizeof(long) - 2)
+
+double
+ldexp(value, exp)
+register double value;
+register int exp;
+{
+	extern double frexp();
+	int old_exp;
+
+	if (exp == 0 || value == 0.0) /* nothing to do for zero */
+		return (value);
+	frexp(value, &old_exp);
+	if (exp > 0) {
+		if (exp + old_exp > MAXBEXP) /* overflow */
+			KILLFPE();
+		for ( ; exp > MAXSHIFT; exp -= MAXSHIFT)
+			value *= (1L << MAXSHIFT);
+		return (value * (1L << exp));
+	}
+	if (exp + old_exp < MINBEXP) /* underflow */
+		return (0.0);
+	for ( ; exp < -MAXSHIFT; exp += MAXSHIFT)
+		value *= 1.0/(1L << MAXSHIFT); /* mult faster than div */
+	return (value / (1L << -exp));
+}