aarch64: Add vector implementations of atan2 routines

1 files changed, 110 insertions, 0 deletions

diff --git a/sysdeps/aarch64/fpu/atan2f_sve.c b/sysdeps/aarch64/fpu/atan2f_sve.c
new file mode 100644
index 0000000000..606a62c144
--- /dev/null
+++ b/sysdeps/aarch64/fpu/atan2f_sve.c
@@ -0,0 +1,110 @@
+/* Single-precision SVE atan2
+
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include "sv_math.h"
+#include "poly_sve_f32.h"
+
+static const struct data
+{
+  float32_t poly[8];
+  float32_t pi_over_2;
+} data = {
+  /* Coefficients of polynomial P such that atan(x)~x+x*P(x^2) on
+     [2**-128, 1.0].  */
+  .poly = { -0x1.55555p-2f, 0x1.99935ep-3f, -0x1.24051ep-3f, 0x1.bd7368p-4f,
+	    -0x1.491f0ep-4f, 0x1.93a2c0p-5f, -0x1.4c3c60p-6f, 0x1.01fd88p-8f },
+  .pi_over_2 = 0x1.921fb6p+0f,
+};
+
+#define SignMask sv_u32 (0x80000000)
+
+/* Special cases i.e. 0, infinity, nan (fall back to scalar calls).  */
+static inline svfloat32_t
+special_case (svfloat32_t y, svfloat32_t x, svfloat32_t ret,
+	      const svbool_t cmp)
+{
+  return sv_call2_f32 (atan2f, y, x, ret, cmp);
+}
+
+/* Returns a predicate indicating true if the input is the bit representation
+   of 0, infinity or nan.  */
+static inline svbool_t
+zeroinfnan (svuint32_t i, const svbool_t pg)
+{
+  return svcmpge (pg, svsub_x (pg, svlsl_x (pg, i, 1), 1),
+		  sv_u32 (2 * 0x7f800000lu - 1));
+}
+
+/* Fast implementation of SVE atan2f based on atan(x) ~ shift + z + z^3 *
+   P(z^2) with reduction to [0,1] using z=1/x and shift = pi/2. Maximum
+   observed error is 2.95 ULP:
+   _ZGVsMxvv_atan2f (0x1.93836cp+6, 0x1.8cae1p+6) got 0x1.967f06p-1
+						 want 0x1.967f00p-1.  */
+svfloat32_t SV_NAME_F2 (atan2) (svfloat32_t y, svfloat32_t x, const svbool_t pg)
+{
+  const struct data *data_ptr = ptr_barrier (&data);
+
+  svuint32_t ix = svreinterpret_u32 (x);
+  svuint32_t iy = svreinterpret_u32 (y);
+
+  svbool_t cmp_x = zeroinfnan (ix, pg);
+  svbool_t cmp_y = zeroinfnan (iy, pg);
+  svbool_t cmp_xy = svorr_z (pg, cmp_x, cmp_y);
+
+  svuint32_t sign_x = svand_x (pg, ix, SignMask);
+  svuint32_t sign_y = svand_x (pg, iy, SignMask);
+  svuint32_t sign_xy = sveor_x (pg, sign_x, sign_y);
+
+  svfloat32_t ax = svabs_x (pg, x);
+  svfloat32_t ay = svabs_x (pg, y);
+
+  svbool_t pred_xlt0 = svcmplt (pg, x, 0.0);
+  svbool_t pred_aygtax = svcmpgt (pg, ay, ax);
+
+  /* Set up z for call to atan.  */
+  svfloat32_t n = svsel (pred_aygtax, svneg_x (pg, ax), ay);
+  svfloat32_t d = svsel (pred_aygtax, ay, ax);
+  svfloat32_t z = svdiv_x (pg, n, d);
+
+  /* Work out the correct shift.  */
+  svfloat32_t shift = svsel (pred_xlt0, sv_f32 (-2.0), sv_f32 (0.0));
+  shift = svsel (pred_aygtax, svadd_x (pg, shift, 1.0), shift);
+  shift = svmul_x (pg, shift, sv_f32 (data_ptr->pi_over_2));
+
+  /* Use split Estrin scheme for P(z^2) with deg(P)=7.  */
+  svfloat32_t z2 = svmul_x (pg, z, z);
+  svfloat32_t z4 = svmul_x (pg, z2, z2);
+  svfloat32_t z8 = svmul_x (pg, z4, z4);
+
+  svfloat32_t ret = sv_estrin_7_f32_x (pg, z2, z4, z8, data_ptr->poly);
+
+  /* ret = shift + z + z^3 * P(z^2).  */
+  svfloat32_t z3 = svmul_x (pg, z2, z);
+  ret = svmla_x (pg, z, z3, ret);
+
+  ret = svadd_m (pg, ret, shift);
+
+  /* Account for the sign of x and y.  */
+  ret = svreinterpret_f32 (sveor_x (pg, svreinterpret_u32 (ret), sign_xy));
+
+  if (__glibc_unlikely (svptest_any (pg, cmp_xy)))
+    return special_case (y, x, ret, cmp_xy);
+
+  return ret;
+}