1 files changed, 49 insertions, 0 deletions
diff --git a/pl/math/atan_common.h b/pl/math/atan_common.h
new file mode 100644
index 0000000..da0da64
--- /dev/null
+++ b/pl/math/atan_common.h
@@ -0,0 +1,49 @@
+/*
+ * Double-precision polynomial evaluation function for scalar and vector atan(x)
+ * and atan2(y,x).
+ *
+ * Copyright (c) 2021-2023, Arm Limited.
+ * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception
+ */
+
+#include "math_config.h"
+#include "estrin.h"
+
+#if V_SUPPORTED
+
+#include "v_math.h"
+
+#define DBL_T v_f64_t
+#define P(i) v_f64 (__atan_poly_data.poly[i])
+
+#else
+
+#define DBL_T double
+#define P(i) __atan_poly_data.poly[i]
+
+#endif
+
+/* Polynomial used in fast atan(x) and atan2(y,x) implementations
+   The order 19 polynomial P approximates (atan(sqrt(x))-sqrt(x))/x^(3/2).  */
+static inline DBL_T
+eval_poly (DBL_T z, DBL_T az, DBL_T shift)
+{
+  /* Use split Estrin scheme for P(z^2) with deg(P)=19. Use split instead of
+     full scheme to avoid underflow in x^16.  */
+  DBL_T z2 = z * z;
+  DBL_T x2 = z2 * z2;
+  DBL_T x4 = x2 * x2;
+  DBL_T x8 = x4 * x4;
+  DBL_T y
+    = FMA (ESTRIN_11_ (z2, x2, x4, x8, P, 8), x8, ESTRIN_7 (z2, x2, x4, P));
+
+  /* Finalize. y = shift + z + z^3 * P(z^2).  */
+  y = FMA (y, z2 * az, az);
+  y = y + shift;
+
+  return y;
+}
+
+#undef DBL_T
+#undef FMA
+#undef P