55 lines
1.7 KiB
C++
55 lines
1.7 KiB
C++
//===-- Single-precision cosh function ------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "src/math/coshf.h"
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#include "src/__support/FPUtil/FPBits.h"
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#include "src/__support/FPUtil/multiply_add.h"
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#include "src/math/generic/expxf.h"
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namespace __llvm_libc {
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LLVM_LIBC_FUNCTION(float, coshf, (float x)) {
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using FPBits = typename fputil::FPBits<float>;
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FPBits xbits(x);
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xbits.set_sign(false);
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x = xbits.get_val();
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uint32_t x_u = xbits.uintval();
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// |x| <= 2^-26
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if (unlikely(x_u <= 0x3280'0000U)) {
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return 1.0f + x;
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}
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// When |x| >= 90, or x is inf or nan
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if (unlikely(x_u >= 0x42b4'0000U)) {
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if (xbits.is_inf_or_nan())
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return x + FPBits::inf().get_val();
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int rounding = fputil::get_round();
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if (unlikely(rounding == FE_DOWNWARD || rounding == FE_TOWARDZERO))
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return FPBits(FPBits::MAX_NORMAL).get_val();
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errno = ERANGE;
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return x + FPBits::inf().get_val();
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}
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auto ep_p = exp_eval<-1>(x);
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auto ep_m = exp_eval<-1>(-x);
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// 0.5 * exp(x) = ep_p.mult_exp * (ep_p.r + 1)
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// = ep_p.mult_exp * ep_p.r + ep_p.mult_exp
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// 0.5 * exp(-x) = ep_m.mult_exp * (ep_m.r + 1)
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// = ep_m.mult_exp * ep_m.r + ep_m.mult_exp
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// cos(x) = 0.5 * exp(x) + 0.5 * expm1(-x)
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double ep = fputil::multiply_add(ep_p.mult_exp, ep_p.r, ep_p.mult_exp) +
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fputil::multiply_add(ep_m.mult_exp, ep_m.r, ep_m.mult_exp);
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return ep;
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}
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} // namespace __llvm_libc
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