1 files changed, 112 insertions, 0 deletions
diff --git a/pl/math/sv_tanf_3u5.c b/pl/math/sv_tanf_3u5.c
new file mode 100644
index 0000000..cca43bd
--- /dev/null
+++ b/pl/math/sv_tanf_3u5.c
@@ -0,0 +1,112 @@
+/*
+ * Single-precision vector tan(x) function.
+ *
+ * Copyright (c) 2020-2023, 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
+
+/* Constants.  */
+#define NegPio2_1 (sv_f32 (-0x1.921fb6p+0f))
+#define NegPio2_2 (sv_f32 (0x1.777a5cp-25f))
+#define NegPio2_3 (sv_f32 (0x1.ee59dap-50f))
+#define InvPio2 (sv_f32 (0x1.45f306p-1f))
+#define RangeVal (sv_f32 (0x1p15f))
+#define Shift (sv_f32 (0x1.8p+23f))
+
+#define poly(i) sv_f32 (__tanf_poly_data.poly_tan[i])
+
+/* Use full Estrin's scheme to evaluate polynomial.  */
+static inline sv_f32_t
+eval_poly (svbool_t pg, sv_f32_t z)
+{
+  sv_f32_t z2 = svmul_f32_x (pg, z, z);
+  sv_f32_t z4 = svmul_f32_x (pg, z2, z2);
+  sv_f32_t y_10 = sv_fma_f32_x (pg, z, poly (1), poly (0));
+  sv_f32_t y_32 = sv_fma_f32_x (pg, z, poly (3), poly (2));
+  sv_f32_t y_54 = sv_fma_f32_x (pg, z, poly (5), poly (4));
+  sv_f32_t y_32_10 = sv_fma_f32_x (pg, z2, y_32, y_10);
+  sv_f32_t y = sv_fma_f32_x (pg, z4, y_54, y_32_10);
+  return y;
+}
+
+static NOINLINE sv_f32_t
+__sv_tanf_specialcase (sv_f32_t x, sv_f32_t y, svbool_t cmp)
+{
+  return sv_call_f32 (tanf, x, y, cmp);
+}
+
+/* Fast implementation of SVE tanf.
+   Maximum error is 3.45 ULP:
+   __sv_tanf(-0x1.e5f0cap+13) got 0x1.ff9856p-1
+			     want 0x1.ff9850p-1.  */
+sv_f32_t
+__sv_tanf_x (sv_f32_t x, const svbool_t pg)
+{
+  /* Determine whether input is too large to perform fast regression.  */
+  svbool_t cmp = svacge_f32 (pg, x, RangeVal);
+  svbool_t pred_minuszero = svcmpeq_f32 (pg, x, sv_f32 (-0.0));
+
+  /* n = rint(x/(pi/2)).  */
+  sv_f32_t q = sv_fma_f32_x (pg, InvPio2, x, Shift);
+  sv_f32_t n = svsub_f32_x (pg, q, Shift);
+  /* n is already a signed integer, simply convert it.  */
+  sv_s32_t in = sv_to_s32_f32_x (pg, n);
+  /* Determine if x lives in an interval, where |tan(x)| grows to infinity.  */
+  sv_s32_t alt = svand_s32_x (pg, in, sv_s32 (1));
+  svbool_t pred_alt = svcmpne_s32 (pg, alt, sv_s32 (0));
+
+  /* r = x - n * (pi/2)  (range reduction into 0 .. pi/4).  */
+  sv_f32_t r;
+  r = sv_fma_f32_x (pg, NegPio2_1, n, x);
+  r = sv_fma_f32_x (pg, NegPio2_2, n, r);
+  r = sv_fma_f32_x (pg, NegPio2_3, n, r);
+
+  /* If x lives in an interval, where |tan(x)|
+     - is finite, then use a polynomial approximation of the form
+       tan(r) ~ r + r^3 * P(r^2) = r + r * r^2 * P(r^2).
+     - grows to infinity then use symmetries of tangent and the identity
+       tan(r) = cotan(pi/2 - r) to express tan(x) as 1/tan(-r). Finally, use
+       the same polynomial approximation of tan as above.  */
+
+  /* Perform additional reduction if required.  */
+  sv_f32_t z = svneg_f32_m (r, pred_alt, r);
+
+  /* Evaluate polynomial approximation of tangent on [-pi/4, pi/4].  */
+  sv_f32_t z2 = svmul_f32_x (pg, z, z);
+  sv_f32_t p = eval_poly (pg, z2);
+  sv_f32_t y = sv_fma_f32_x (pg, svmul_f32_x (pg, z, z2), p, z);
+
+  /* Transform result back, if necessary.  */
+  sv_f32_t inv_y = svdiv_f32_x (pg, sv_f32 (1.0f), y);
+  y = svsel_f32 (pred_alt, inv_y, y);
+
+  /* Fast reduction does not handle the x = -0.0 case well,
+     therefore it is fixed here.  */
+  y = svsel_f32 (pred_minuszero, x, y);
+
+  /* No need to pass pg to specialcase here since cmp is a strict subset,
+     guaranteed by the cmpge above.  */
+  if (unlikely (svptest_any (pg, cmp)))
+    return __sv_tanf_specialcase (x, y, cmp);
+  return y;
+}
+
+PL_ALIAS (__sv_tanf_x, _ZGVsMxv_tanf)
+
+PL_SIG (SV, F, 1, tan, -3.1, 3.1)
+PL_TEST_ULP (__sv_tanf, 2.96)
+PL_TEST_INTERVAL (__sv_tanf, -0.0, -0x1p126, 100)
+PL_TEST_INTERVAL (__sv_tanf, 0x1p-149, 0x1p-126, 4000)
+PL_TEST_INTERVAL (__sv_tanf, 0x1p-126, 0x1p-23, 50000)
+PL_TEST_INTERVAL (__sv_tanf, 0x1p-23, 0.7, 50000)
+PL_TEST_INTERVAL (__sv_tanf, 0.7, 1.5, 50000)
+PL_TEST_INTERVAL (__sv_tanf, 1.5, 100, 50000)
+PL_TEST_INTERVAL (__sv_tanf, 100, 0x1p17, 50000)
+PL_TEST_INTERVAL (__sv_tanf, 0x1p17, inf, 50000)
+#endif