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1//===-- Collection of utils for acoshf --------------------------*- C++ -*-===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8 9#ifndef LLVM_LIBC_SRC___SUPPORT_MATH_ACOSHF_UTILS_H10#define LLVM_LIBC_SRC___SUPPORT_MATH_ACOSHF_UTILS_H11 12#include "acosh_float_constants.h"13#include "src/__support/FPUtil/FPBits.h"14#include "src/__support/FPUtil/PolyEval.h"15#include "src/__support/FPUtil/multiply_add.h"16 17namespace LIBC_NAMESPACE_DECL {18 19namespace acoshf_internal {20 21// x should be positive, normal finite value22LIBC_INLINE static double log_eval(double x) {23 // For x = 2^ex * (1 + mx)24 // log(x) = ex * log(2) + log(1 + mx)25 using FPB = fputil::FPBits<double>;26 FPB bs(x);27 28 double ex = static_cast<double>(bs.get_exponent());29 30 // p1 is the leading 7 bits of mx, i.e.31 // p1 * 2^(-7) <= m_x < (p1 + 1) * 2^(-7).32 int p1 = static_cast<int>(bs.get_mantissa() >> (FPB::FRACTION_LEN - 7));33 34 // Set bs to (1 + (mx - p1*2^(-7))35 bs.set_uintval(bs.uintval() & (FPB::FRACTION_MASK >> 7));36 bs.set_biased_exponent(FPB::EXP_BIAS);37 // dx = (mx - p1*2^(-7)) / (1 + p1*2^(-7)).38 double dx = (bs.get_val() - 1.0) * ONE_OVER_F[p1];39 40 // Minimax polynomial of log(1 + dx) generated by Sollya with:41 // > P = fpminimax(log(1 + x)/x, 6, [|D...|], [0, 2^-7]);42 const double COEFFS[6] = {-0x1.ffffffffffffcp-2, 0x1.5555555552ddep-2,43 -0x1.ffffffefe562dp-3, 0x1.9999817d3a50fp-3,44 -0x1.554317b3f67a5p-3, 0x1.1dc5c45e09c18p-3};45 double dx2 = dx * dx;46 double c1 = fputil::multiply_add(dx, COEFFS[1], COEFFS[0]);47 double c2 = fputil::multiply_add(dx, COEFFS[3], COEFFS[2]);48 double c3 = fputil::multiply_add(dx, COEFFS[5], COEFFS[4]);49 50 double p = fputil::polyeval(dx2, dx, c1, c2, c3);51 double result =52 fputil::multiply_add(ex, /*log(2)*/ 0x1.62e42fefa39efp-1, LOG_F[p1] + p);53 return result;54}55 56} // namespace acoshf_internal57 58} // namespace LIBC_NAMESPACE_DECL59 60#endif // LLVM_LIBC_SRC___SUPPORT_MATH_ACOSHF_UTILS_H61