1 files changed, 59 insertions, 0 deletions
diff --git a/sysdeps/aarch64/fpu/atanh_sve.c b/sysdeps/aarch64/fpu/atanh_sve.c
new file mode 100644
index 0000000000..7a52728d70
--- /dev/null
+++ b/sysdeps/aarch64/fpu/atanh_sve.c
@@ -0,0 +1,59 @@
+/* Double-precision vector (SVE) atanh function
+
+   Copyright (C) 2024 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/>.  */
+
+#define WANT_SV_LOG1P_K0_SHORTCUT 0
+#include "sv_log1p_inline.h"
+
+#define One (0x3ff0000000000000)
+#define Half (0x3fe0000000000000)
+
+static svfloat64_t NOINLINE
+special_case (svfloat64_t x, svfloat64_t y, svbool_t special)
+{
+  return sv_call_f64 (atanh, x, y, special);
+}
+
+/* SVE approximation for double-precision atanh, based on log1p.
+   The greatest observed error is 2.81 ULP:
+   _ZGVsMxv_atanh(0x1.ffae6288b601p-6) got 0x1.ffd8ff31b5019p-6
+				      want 0x1.ffd8ff31b501cp-6.  */
+svfloat64_t SV_NAME_D1 (atanh) (svfloat64_t x, const svbool_t pg)
+{
+
+  svfloat64_t ax = svabs_x (pg, x);
+  svuint64_t iax = svreinterpret_u64 (ax);
+  svuint64_t sign = sveor_x (pg, svreinterpret_u64 (x), iax);
+  svfloat64_t halfsign = svreinterpret_f64 (svorr_x (pg, sign, Half));
+
+  /* It is special if iax >= 1.  */
+//   svbool_t special = svcmpge (pg, iax, One);
+  svbool_t special = svacge (pg, x, 1.0);
+
+  /* Computation is performed based on the following sequence of equality:
+	(1+x)/(1-x) = 1 + 2x/(1-x).  */
+  svfloat64_t y;
+  y = svadd_x (pg, ax, ax);
+  y = svdiv_x (pg, y, svsub_x (pg, sv_f64 (1), ax));
+  /* ln((1+x)/(1-x)) = ln(1+2x/(1-x)) = ln(1 + y).  */
+  y = sv_log1p_inline (y, pg);
+
+  if (__glibc_unlikely (svptest_any (pg, special)))
+    return special_case (x, svmul_x (pg, halfsign, y), special);
+  return svmul_x (pg, halfsign, y);
+}