Snap for 10447354 from 172d24a7ae67ee7bae413d5a8618f1b5edc002be to mainline-cellbroadcast-releaseaml_cbr_341710000aml_cbr_341610000aml_cbr_341510010aml_cbr_341410010aml_cbr_341311010aml_cbr_341110000aml_cbr_341011000aml_cbr_340914000android14-mainline-cellbroadcast-release

Change-Id: I8753ae14d61308952964b5f87c7e48044f60727c

1 files changed, 51 insertions, 0 deletions

diff --git a/pl/math/atanf_common.h b/pl/math/atanf_common.h
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--- /dev/null
+++ b/pl/math/atanf_common.h
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+/*
+ * Single-precision polynomial evaluation function for scalar and vector
+ * atan(x) and atan2(y,x).
+ *
+ * Copyright (c) 2021-2023, Arm Limited.
+ * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception
+ */
+
+#ifndef PL_MATH_ATANF_COMMON_H
+#define PL_MATH_ATANF_COMMON_H
+
+#include "math_config.h"
+#include "estrinf.h"
+
+#if V_SUPPORTED
+
+#include "v_math.h"
+
+#define FLT_T v_f32_t
+#define P(i) v_f32 (__atanf_poly_data.poly[i])
+
+#else
+
+#define FLT_T float
+#define P(i) __atanf_poly_data.poly[i]
+
+#endif
+
+/* Polynomial used in fast atanf(x) and atan2f(y,x) implementations
+   The order 7 polynomial P approximates (atan(sqrt(x))-sqrt(x))/x^(3/2).  */
+static inline FLT_T
+eval_poly (FLT_T z, FLT_T az, FLT_T shift)
+{
+  /* Use 2-level Estrin scheme for P(z^2) with deg(P)=7. However,
+     a standard implementation using z8 creates spurious underflow
+     in the very last fma (when z^8 is small enough).
+     Therefore, we split the last fma into a mul and and an fma.
+     Horner and single-level Estrin have higher errors that exceed
+     threshold.  */
+  FLT_T z2 = z * z;
+  FLT_T z4 = z2 * z2;
+
+  /* Then assemble polynomial.  */
+  FLT_T y = FMA (z4, z4 * ESTRIN_3_ (z2, z4, P, 4), ESTRIN_3 (z2, z4, P));
+
+  /* Finalize:
+     y = shift + z * P(z^2).  */
+  return FMA (y, z2 * az, az) + shift;
+}
+
+#endif // PL_MATH_ATANF_COMMON_H