| //===-- Single-precision tanh function ------------------------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "src/math/tanhf.h" |
| #include "src/__support/FPUtil/FPBits.h" |
| #include "src/math/generic/expxf.h" |
| |
| namespace __llvm_libc { |
| |
| LLVM_LIBC_FUNCTION(float, tanhf, (float x)) { |
| using FPBits = typename fputil::FPBits<float>; |
| FPBits xbits(x); |
| bool sign = xbits.get_sign(); |
| uint32_t x_abs = xbits.uintval() & FPBits::FloatProp::EXP_MANT_MASK; |
| |
| // |x| <= 2^-26 |
| if (unlikely(x_abs <= 0x3280'0000U)) { |
| return unlikely(x_abs == 0) ? x : (x - 0x1.5555555555555p-2 * x * x * x); |
| } |
| |
| // When |x| >= 15, or x is inf or nan |
| if (unlikely(x_abs >= 0x4170'0000U)) { |
| if (xbits.is_nan()) |
| return x + 1.0f; // sNaN to qNaN + signal |
| |
| if (xbits.is_inf()) |
| return sign ? -1.0f : 1.0f; |
| |
| if (sign) { |
| return -1.0f + opt_barrier(FPBits(FPBits::MIN_NORMAL).get_val()); |
| } else |
| return 1.0f - opt_barrier(FPBits(FPBits::MIN_NORMAL).get_val()); |
| } |
| |
| // |x| <= 0.078125 |
| if (unlikely(x_abs <= 0x3da0'0000U)) { |
| double xdbl = x; |
| double x2 = xdbl * xdbl; |
| // Pure Taylor series. |
| double pe = fputil::polyeval(x2, 0.0, -0x1.5555555555555p-2, |
| 0x1.1111111111111p-3, -0x1.ba1ba1ba1ba1cp-5, |
| 0x1.664f4882c10fap-6, -0x1.226e355e6c23dp-7); |
| return fputil::multiply_add(xdbl, pe, xdbl); |
| } |
| |
| if (unlikely(xbits.bits == 0x4058'e0a3U)) { |
| if (fputil::get_round() == FE_DOWNWARD) |
| return FPBits(0x3f7f'6ad9U).get_val(); |
| } |
| |
| auto ep = exp_eval(2.0f * (sign ? x : -x)); // exp(-2 * x) |
| double result = fputil::multiply_add(ep.mult_exp, ep.r, ep.mult_exp - 1.0) / |
| (fputil::multiply_add(ep.mult_exp, ep.r, ep.mult_exp + 1.0)); |
| return sign ? result : -result; |
| } |
| |
| } // namespace __llvm_libc |