1 files changed, 12 insertions, 0 deletions
diff --git a/lib/libm/copysign.c b/lib/libm/copysign.c
new file mode 100644
index 00000000..26982cea
--- /dev/null
+++ b/lib/libm/copysign.c
@@ -0,0 +1,12 @@
+#include "libm.h"
+
+double copysign(double x, double y)
+{
+	union {
+		double f;
+		uint64_t i;
+	} ux = { x }, uy = { y };
+	ux.i &= -1ULL / 2;
+	ux.i |= uy.i & 1ULL << 63;
+	return ux.f;
+}