1 files changed, 76 insertions, 0 deletions
diff --git a/pl/math/sv_asinf_2u5.c b/pl/math/sv_asinf_2u5.c
new file mode 100644
index 000000000000..8e9edc2439f5
--- /dev/null
+++ b/pl/math/sv_asinf_2u5.c
@@ -0,0 +1,76 @@
+/*
+ * Single-precision SVE asin(x) function.
+ *
+ * Copyright (c) 2023, Arm Limited.
+ * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception
+ */
+
+#include "sv_math.h"
+#include "poly_sve_f32.h"
+#include "pl_sig.h"
+#include "pl_test.h"
+
+static const struct data
+{
+  float32_t poly[5];
+  float32_t pi_over_2f;
+} data = {
+  /* Polynomial approximation of  (asin(sqrt(x)) - sqrt(x)) / (x * sqrt(x))  on
+    [ 0x1p-24 0x1p-2 ] order = 4 rel error: 0x1.00a23bbp-29 .  */
+  .poly = { 0x1.55555ep-3, 0x1.33261ap-4, 0x1.70d7dcp-5, 0x1.b059dp-6,
+	    0x1.3af7d8p-5, },
+  .pi_over_2f = 0x1.921fb6p+0f,
+};
+
+/* Single-precision SVE implementation of vector asin(x).
+
+   For |x| in [0, 0.5], use order 4 polynomial P such that the final
+   approximation is an odd polynomial: asin(x) ~ x + x^3 P(x^2).
+
+    The largest observed error in this region is 0.83 ulps,
+      _ZGVsMxv_asinf (0x1.ea00f4p-2) got 0x1.fef15ep-2
+				    want 0x1.fef15cp-2.
+
+    For |x| in [0.5, 1.0], use same approximation with a change of variable
+
+    asin(x) = pi/2 - (y + y * z * P(z)), with  z = (1-x)/2 and y = sqrt(z).
+
+   The largest observed error in this region is 2.41 ulps,
+     _ZGVsMxv_asinf (-0x1.00203ep-1) got -0x1.0c3a64p-1
+				    want -0x1.0c3a6p-1.  */
+svfloat32_t SV_NAME_F1 (asin) (svfloat32_t x, const svbool_t pg)
+{
+  const struct data *d = ptr_barrier (&data);
+
+  svuint32_t sign = svand_x (pg, svreinterpret_u32 (x), 0x80000000);
+
+  svfloat32_t ax = svabs_x (pg, x);
+  svbool_t a_ge_half = svacge (pg, x, 0.5);
+
+  /* Evaluate polynomial Q(x) = y + y * z * P(z) with
+   z = x ^ 2 and y = |x|            , if |x| < 0.5
+   z = (1 - |x|) / 2 and y = sqrt(z), if |x| >= 0.5.  */
+  svfloat32_t z2 = svsel (a_ge_half, svmls_x (pg, sv_f32 (0.5), ax, 0.5),
+			  svmul_x (pg, x, x));
+  svfloat32_t z = svsqrt_m (ax, a_ge_half, z2);
+
+  /* Use a single polynomial approximation P for both intervals.  */
+  svfloat32_t p = sv_horner_4_f32_x (pg, z2, d->poly);
+  /* Finalize polynomial: z + z * z2 * P(z2).  */
+  p = svmla_x (pg, z, svmul_x (pg, z, z2), p);
+
+  /* asin(|x|) = Q(|x|)         , for |x| < 0.5
+		 = pi/2 - 2 Q(|x|), for |x| >= 0.5.  */
+  svfloat32_t y = svmad_m (a_ge_half, p, sv_f32 (-2.0), d->pi_over_2f);
+
+  /* Copy sign.  */
+  return svreinterpret_f32 (svorr_x (pg, svreinterpret_u32 (y), sign));
+}
+
+PL_SIG (SV, F, 1, asin, -1.0, 1.0)
+PL_TEST_ULP (SV_NAME_F1 (asin), 1.91)
+PL_TEST_INTERVAL (SV_NAME_F1 (asin), 0, 0.5, 50000)
+PL_TEST_INTERVAL (SV_NAME_F1 (asin), 0.5, 1.0, 50000)
+PL_TEST_INTERVAL (SV_NAME_F1 (asin), 1.0, 0x1p11, 50000)
+PL_TEST_INTERVAL (SV_NAME_F1 (asin), 0x1p11, inf, 20000)
+PL_TEST_INTERVAL (SV_NAME_F1 (asin), -0, -inf, 20000)
+\ No newline at end of file