1 files changed, 45 insertions, 0 deletions
diff --git a/lib/libm/nexttoward.c b/lib/libm/nexttoward.c
new file mode 100644
index 00000000..2082dff1
--- /dev/null
+++ b/lib/libm/nexttoward.c
@@ -0,0 +1,45 @@
+#include "libm.h"
+
+#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
+double nexttoward(double x, long double y)
+{
+	return nextafter(x, y);
+}
+#else
+double nexttoward(double x, long double y)
+{
+	union {
+		double f;
+		uint64_t i;
+	} ux = { x };
+	int e;
+
+	if (isnan(x) || isnan(y))
+		return x + y;
+	if (x == y)
+		return y;
+	if (x == 0) {
+		ux.i = 1;
+		if (signbit(y))
+			ux.i |= 1ULL << 63;
+	} else if (x < y) {
+		if (signbit(x))
+			ux.i--;
+		else
+			ux.i++;
+	} else {
+		if (signbit(x))
+			ux.i++;
+		else
+			ux.i--;
+	}
+	e = ux.i >> 52 & 0x7ff;
+	/* raise overflow if ux.f is infinite and x is finite */
+	if (e == 0x7ff)
+		FORCE_EVAL(x + x);
+	/* raise underflow if ux.f is subnormal or zero */
+	if (e == 0)
+		FORCE_EVAL(x * x + ux.f * ux.f);
+	return ux.f;
+}
+#endif