1 files changed, 57 insertions, 0 deletions
diff --git a/libquadmath/math/sqrtq.c b/libquadmath/math/sqrtq.c
new file mode 100644
index 000000000..6ed4605ed
--- /dev/null
+++ b/libquadmath/math/sqrtq.c
@@ -0,0 +1,57 @@
+#include "quadmath-imp.h"
+#include <math.h>
+#include <float.h>
+
+__float128
+sqrtq (const __float128 x)
+{
+  __float128 y;
+  int exp;
+
+  if (x == 0)
+    return x;
+
+  if (isnanq (x))
+    return x;
+
+  if (x < 0)
+    return nanq ("");
+
+  if (x <= DBL_MAX && x >= DBL_MIN)
+  {
+    /* Use double result as starting point.  */
+    y = sqrt ((double) x);
+
+    /* Two Newton iterations.  */
+    y -= 0.5q * (y - x / y);
+    y -= 0.5q * (y - x / y);
+    return y;
+  }
+
+#ifdef HAVE_SQRTL
+  if (x <= LDBL_MAX && x >= LDBL_MIN)
+  {
+    /* Use long double result as starting point.  */
+    y = sqrtl ((long double) x);
+
+    /* One Newton iteration.  */
+    y -= 0.5q * (y - x / y);
+    return y;
+  }
+#endif
+
+  /* If we're outside of the range of C types, we have to compute
+     the initial guess the hard way.  */
+  y = frexpq (x, &exp);
+  if (exp % 2)
+    y *= 2, exp--;
+
+  y = sqrt (y);
+  y = scalbnq (y, exp / 2);
+
+  /* Two Newton iterations.  */
+  y -= 0.5q * (y - x / y);
+  y -= 0.5q * (y - x / y);
+  return y;
+}
+