1 files changed, 94 insertions, 0 deletions
diff --git a/pl/math/v_tanh_3u.c b/pl/math/v_tanh_3u.c
new file mode 100644
index 0000000..c8b6c25
--- /dev/null
+++ b/pl/math/v_tanh_3u.c
@@ -0,0 +1,94 @@
+/*
+ * Double-precision vector tanh(x) function.
+ * Copyright (c) 2023, Arm Limited.
+ * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception
+ */
+
+#include "v_math.h"
+#include "estrin.h"
+#include "mathlib.h"
+#include "pl_sig.h"
+#include "pl_test.h"
+
+#if V_SUPPORTED
+
+#define AbsMask v_u64 (0x7fffffffffffffff)
+#define InvLn2 v_f64 (0x1.71547652b82fep0)
+#define MLn2hi v_f64 (-0x1.62e42fefa39efp-1)
+#define MLn2lo v_f64 (-0x1.abc9e3b39803fp-56)
+#define Shift v_f64 (0x1.8p52)
+#define C(i) v_f64 (__expm1_poly[i])
+
+#define BoringBound 0x403241bf835f9d5f /* asuint64 (0x1.241bf835f9d5fp+4).  */
+#define TinyBound 0x3e40000000000000   /* asuint64 (0x1p-27).  */
+#define One v_u64 (0x3ff0000000000000)
+
+static inline v_f64_t
+expm1_inline (v_f64_t x)
+{
+  /* Helper routine for calculating exp(x) - 1. Vector port of the helper from
+     the scalar variant of tanh.  */
+
+  /* Reduce argument: f in [-ln2/2, ln2/2], i is exact.  */
+  v_f64_t j = v_fma_f64 (InvLn2, x, Shift) - Shift;
+  v_s64_t i = v_to_s64_f64 (j);
+  v_f64_t f = v_fma_f64 (j, MLn2hi, x);
+  f = v_fma_f64 (j, MLn2lo, f);
+
+  /* Approximate expm1(f) using polynomial.  */
+  v_f64_t f2 = f * f;
+  v_f64_t f4 = f2 * f2;
+  v_f64_t p = v_fma_f64 (f2, ESTRIN_10 (f, f2, f4, f4 * f4, C), f);
+
+  /* t = 2 ^ i.  */
+  v_f64_t t = v_as_f64_u64 (v_as_u64_s64 (i << 52) + One);
+  /* expm1(x) = p * t + (t - 1).  */
+  return v_fma_f64 (p, t, t - 1);
+}
+
+static NOINLINE v_f64_t
+special_case (v_f64_t x, v_f64_t y, v_u64_t special)
+{
+  return v_call_f64 (tanh, x, y, special);
+}
+
+/* Vector approximation for double-precision tanh(x), using a simplified
+   version of expm1. The greatest observed error is 2.75 ULP:
+   __v_tanh(-0x1.c143c3a44e087p-3) got -0x1.ba31ba4691ab7p-3
+				  want -0x1.ba31ba4691ab4p-3.  */
+VPCS_ATTR v_f64_t V_NAME (tanh) (v_f64_t x)
+{
+  v_u64_t ix = v_as_u64_f64 (x);
+  v_u64_t ia = ix & AbsMask;
+
+  /* Trigger special-cases for tiny, boring and infinity/NaN.  */
+  v_u64_t special = v_cond_u64 ((ia - TinyBound) > (BoringBound - TinyBound));
+  v_f64_t u;
+
+  /* To trigger fp exceptions correctly, set special lanes to a neutral value.
+     They will be fixed up later by the special-case handler.  */
+  if (unlikely (v_any_u64 (special)))
+    u = v_sel_f64 (special, v_f64 (1), x) * 2;
+  else
+    u = x * 2;
+
+  /* tanh(x) = (e^2x - 1) / (e^2x + 1).  */
+  v_f64_t q = expm1_inline (u);
+  v_f64_t y = q / (q + 2);
+
+  if (unlikely (v_any_u64 (special)))
+    return special_case (x, y, special);
+  return y;
+}
+VPCS_ALIAS
+
+PL_SIG (V, D, 1, tanh, -10.0, 10.0)
+PL_TEST_ULP (V_NAME (tanh), 2.26)
+PL_TEST_EXPECT_FENV_ALWAYS (V_NAME (tanh))
+PL_TEST_INTERVAL (V_NAME (tanh), 0, TinyBound, 1000)
+PL_TEST_INTERVAL (V_NAME (tanh), -0, -TinyBound, 1000)
+PL_TEST_INTERVAL (V_NAME (tanh), TinyBound, BoringBound, 100000)
+PL_TEST_INTERVAL (V_NAME (tanh), -TinyBound, -BoringBound, 100000)
+PL_TEST_INTERVAL (V_NAME (tanh), BoringBound, inf, 1000)
+PL_TEST_INTERVAL (V_NAME (tanh), -BoringBound, -inf, 1000)
+#endif