1 files changed, 59 insertions, 0 deletions
diff --git a/pl/math/sv_atanf_2u9.c b/pl/math/sv_atanf_2u9.c
new file mode 100644
index 0000000..8d38e42
--- /dev/null
+++ b/pl/math/sv_atanf_2u9.c
@@ -0,0 +1,59 @@
+/*
+ * Single-precision vector atan(x) function.
+ *
+ * Copyright (c) 2021-2023, Arm Limited.
+ * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception
+ */
+
+#include "sv_math.h"
+#include "pl_sig.h"
+#include "pl_test.h"
+
+#if SV_SUPPORTED
+
+#include "sv_atanf_common.h"
+
+#define PiOver2 sv_f32 (0x1.921fb6p+0f)
+#define AbsMask (0x7fffffff)
+
+/* Fast implementation of SVE atanf based on
+   atan(x) ~ shift + z + z^3 * P(z^2) with reduction to [0,1] using
+   z=-1/x and shift = pi/2.
+   Largest observed error is 2.9 ULP, close to +/-1.0:
+   __sv_atanf(0x1.0468f6p+0) got -0x1.967f06p-1
+			    want -0x1.967fp-1.  */
+sv_f32_t
+__sv_atanf_x (sv_f32_t x, const svbool_t pg)
+{
+  /* No need to trigger special case. Small cases, infs and nans
+     are supported by our approximation technique.  */
+  sv_u32_t ix = sv_as_u32_f32 (x);
+  sv_u32_t sign = svand_n_u32_x (pg, ix, ~AbsMask);
+
+  /* Argument reduction:
+     y := arctan(x) for x < 1
+     y := pi/2 + arctan(-1/x) for x > 1
+     Hence, use z=-1/a if x>=1, otherwise z=a.  */
+  svbool_t red = svacgt_n_f32 (pg, x, 1.0f);
+  /* Avoid dependency in abs(x) in division (and comparison).  */
+  sv_f32_t z = svsel_f32 (red, svdiv_f32_x (pg, sv_f32 (-1.0f), x), x);
+  /* Use absolute value only when needed (odd powers of z).  */
+  sv_f32_t az = svabs_f32_x (pg, z);
+  az = svneg_f32_m (az, red, az);
+
+  sv_f32_t y = __sv_atanf_common (pg, red, z, az, PiOver2);
+
+  /* y = atan(x) if x>0, -atan(-x) otherwise.  */
+  return sv_as_f32_u32 (sveor_u32_x (pg, sv_as_u32_f32 (y), sign));
+}
+
+PL_ALIAS (__sv_atanf_x, _ZGVsMxv_atanf)
+
+PL_SIG (SV, F, 1, atan, -3.1, 3.1)
+PL_TEST_ULP (__sv_atanf, 2.9)
+PL_TEST_INTERVAL (__sv_atanf, -10.0, 10.0, 50000)
+PL_TEST_INTERVAL (__sv_atanf, -1.0, 1.0, 40000)
+PL_TEST_INTERVAL (__sv_atanf, 0.0, 1.0, 40000)
+PL_TEST_INTERVAL (__sv_atanf, 1.0, 100.0, 40000)
+PL_TEST_INTERVAL (__sv_atanf, 1e6, 1e32, 40000)
+#endif