1 files changed, 60 insertions, 0 deletions
diff --git a/lib/libm/csqrt.c b/lib/libm/csqrt.c
new file mode 100644
index 00000000..e98cb7c6
--- /dev/null
+++ b/lib/libm/csqrt.c
@@ -0,0 +1,60 @@
+#include "__complex.h"
+
+double complex csqrt(double complex z)
+{
+	double complex w;
+	double x, y, r, t, scale;
+
+	x = creal(z);
+	y = cimag(z);
+	if (y == 0.0) {
+		if (x == 0.0) {
+			return 0.0 + y * (double complex)I;
+		} else {
+			r = fabs(x);
+			r = sqrt(r);
+			if (x < 0.0) {
+				return 0.0 + r * (double complex)I;
+			} else {
+				return r + y * (double complex)I;
+			}
+		}
+	}
+
+	if (x == 0.0) {
+		r = fabs(y);
+		r = sqrt(0.5 * r);
+
+		if (y > 0)
+			return r + r * (double complex)I;
+		else
+			return r - r * (double complex)I;
+	}
+
+	if ((fabs(x) > 4.0) || (fabs(y) > 4.0)) {
+		x *= 0.25;
+		y *= 0.25;
+		scale = 2.0;
+	} else {
+		x *= 1.8014398509481984e16; /* 2^54 */
+		y *= 1.8014398509481984e16;
+		scale = 7.450580596923828125e-9; /* 2^-27 */
+	}
+
+	w = x + y * (double complex)I;
+	r = cabs(w);
+	if (x > 0) {
+		t = sqrt(0.5 * r + 0.5 * x);
+		r = scale * fabs((0.5 * y) / t);
+		t *= scale;
+	} else {
+		r = sqrt(0.5 * r - 0.5 * x);
+		t = scale * fabs((0.5 * y) / r);
+		r *= scale;
+	}
+
+	if (y < 0)
+		return t - r * (double complex)I;
+	else
+		return t + r * (double complex)I;
+}