libc/src/math/generic/atanf.cpp

   1 //===-- Single-precision atan function ------------------------------------===//
   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-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "src/math/atanf.h"
  10 #include "math_utils.h"
  11 #include "src/__support/FPUtil/FPBits.h"
  12 #include "src/__support/macros/optimization.h" // LIBC_UNLIKELY
  13 #include "src/math/generic/inv_trigf_utils.h"
  14
  15 namespace __llvm_libc {
  16
  17 LLVM_LIBC_FUNCTION(float, atanf, (float x)) {
  18   using FPBits = typename fputil::FPBits<float>;
  19   FPBits xbits(x);
  20   bool sign = xbits.get_sign();
  21   xbits.set_sign(false);
  22
  23   if (LIBC_UNLIKELY(xbits.is_inf_or_nan())) {
  24     if (xbits.is_inf())
  25       return static_cast<float>(opt_barrier(sign ? -M_MATH_PI_2 : M_MATH_PI_2));
  26     else
  27       return x;
  28   }
  29   // |x| == 0.06905200332403183
  30   if (LIBC_UNLIKELY(xbits.uintval() == 0x3d8d6b23U)) {
  31     if (fputil::get_round() == FE_TONEAREST) {
  32       // 0.06894256919622421
  33       FPBits br(0x3d8d31c3U);
  34       br.set_sign(sign);
  35       return br.get_val();
  36     }
  37   }
  38
  39   // |x| == 1.8670953512191772
  40   if (LIBC_UNLIKELY(xbits.uintval() == 0x3feefcfbU)) {
  41     int rounding_mode = fputil::get_round();
  42     if (sign) {
  43       if (rounding_mode == FE_DOWNWARD) {
  44         // -1.0790828466415405
  45         return FPBits(0xbf8a1f63U).get_val();
  46       }
  47     } else {
  48       if (rounding_mode == FE_UPWARD) {
  49         // 1.0790828466415405
  50         return FPBits(0x3f8a1f63U).get_val();
  51       }
  52     }
  53   }
  54
  55   return static_cast<float>(atan_eval(x));
  56 }
  57
  58 } // namespace __llvm_libc