1 files changed, 38 insertions, 0 deletions
diff --git a/lib/libm/round.c b/lib/libm/round.c
new file mode 100644
index 00000000..aa36cce4
--- /dev/null
+++ b/lib/libm/round.c
@@ -0,0 +1,38 @@
+#include "libm.h"
+
+#if FLT_EVAL_METHOD == 0 || FLT_EVAL_METHOD == 1
+#define EPS DBL_EPSILON
+#elif FLT_EVAL_METHOD == 2
+#define EPS LDBL_EPSILON
+#endif
+static const double_t toint = 1 / EPS;
+
+double round(double x)
+{
+	union {
+		double f;
+		uint64_t i;
+	} u = { x };
+	int e = u.i >> 52 & 0x7ff;
+	double_t y;
+
+	if (e >= 0x3ff + 52)
+		return x;
+	if (u.i >> 63)
+		x = -x;
+	if (e < 0x3ff - 1) {
+		/* raise inexact if x!=0 */
+		FORCE_EVAL(x + toint);
+		return 0 * u.f;
+	}
+	y = x + toint - toint - x;
+	if (y > 0.5)
+		y = y + x - 1;
+	else if (y <= -0.5)
+		y = y + x + 1;
+	else
+		y = y + x;
+	if (u.i >> 63)
+		y = -y;
+	return y;
+}