diff options
Diffstat (limited to 'libc/src/math/generic/acoshf16.cpp')
| -rw-r--r-- | libc/src/math/generic/acoshf16.cpp | 98 |
1 files changed, 2 insertions, 96 deletions
diff --git a/libc/src/math/generic/acoshf16.cpp b/libc/src/math/generic/acoshf16.cpp index 44783a8..bb3a91f 100644 --- a/libc/src/math/generic/acoshf16.cpp +++ b/libc/src/math/generic/acoshf16.cpp @@ -7,104 +7,10 @@ //===----------------------------------------------------------------------===// #include "src/math/acoshf16.h" -#include "explogxf.h" -#include "hdr/errno_macros.h" -#include "hdr/fenv_macros.h" -#include "src/__support/FPUtil/FEnvImpl.h" -#include "src/__support/FPUtil/FPBits.h" -#include "src/__support/FPUtil/PolyEval.h" -#include "src/__support/FPUtil/cast.h" -#include "src/__support/FPUtil/except_value_utils.h" -#include "src/__support/FPUtil/multiply_add.h" -#include "src/__support/FPUtil/sqrt.h" -#include "src/__support/common.h" -#include "src/__support/macros/config.h" -#include "src/__support/macros/optimization.h" +#include "src/__support/math/acoshf16.h" namespace LIBC_NAMESPACE_DECL { -static constexpr size_t N_EXCEPTS = 2; -static constexpr fputil::ExceptValues<float16, N_EXCEPTS> ACOSHF16_EXCEPTS{{ - // (input, RZ output, RU offset, RD offset, RN offset) - // x = 0x1.6dcp+1, acoshf16(x) = 0x1.b6p+0 (RZ) - {0x41B7, 0x3ED8, 1, 0, 0}, - // x = 0x1.39p+0, acoshf16(x) = 0x1.4f8p-1 (RZ) - {0x3CE4, 0x393E, 1, 0, 1}, -}}; - -LLVM_LIBC_FUNCTION(float16, acoshf16, (float16 x)) { - using FPBits = fputil::FPBits<float16>; - FPBits xbits(x); - uint16_t x_u = xbits.uintval(); - - // Check for NaN input first. - if (LIBC_UNLIKELY(xbits.is_inf_or_nan())) { - if (xbits.is_signaling_nan()) { - fputil::raise_except_if_required(FE_INVALID); - return FPBits::quiet_nan().get_val(); - } - if (xbits.is_neg()) { - fputil::set_errno_if_required(EDOM); - fputil::raise_except_if_required(FE_INVALID); - return FPBits::quiet_nan().get_val(); - } - return x; - } - - // Domain error for inputs less than 1.0. - if (LIBC_UNLIKELY(x <= 1.0f)) { - if (x == 1.0f) - return FPBits::zero().get_val(); - fputil::set_errno_if_required(EDOM); - fputil::raise_except_if_required(FE_INVALID); - return FPBits::quiet_nan().get_val(); - } - - if (auto r = ACOSHF16_EXCEPTS.lookup(xbits.uintval()); - LIBC_UNLIKELY(r.has_value())) - return r.value(); - - float xf = x; - // High-precision polynomial approximation for inputs close to 1.0 - // ([1, 1.25)). - // - // Brief derivation: - // 1. Expand acosh(1 + delta) using Taylor series around delta=0: - // acosh(1 + delta) ≈ sqrt(2 * delta) * [1 - delta/12 + 3*delta^2/160 - // - 5*delta^3/896 + 35*delta^4/18432 + ...] - // 2. Truncate the series to fit accurately for delta in [0, 0.25]. - // 3. Polynomial coefficients (from sollya) used here are: - // P(delta) ≈ 1 - 0x1.555556p-4 * delta + 0x1.333334p-6 * delta^2 - // - 0x1.6db6dcp-8 * delta^3 + 0x1.f1c71cp-10 * delta^4 - // 4. The Sollya commands used to generate these coefficients were: - // > display = hexadecimal; - // > round(1/12, SG, RN); - // > round(3/160, SG, RN); - // > round(5/896, SG, RN); - // > round(35/18432, SG, RN); - // With hexadecimal display mode enabled, the outputs were: - // 0x1.555556p-4 - // 0x1.333334p-6 - // 0x1.6db6dcp-8 - // 0x1.f1c71cp-10 - // 5. The maximum absolute error, estimated using: - // dirtyinfnorm(acosh(1 + x) - sqrt(2*x) * P(x), [0, 0.25]) - // is: - // 0x1.d84281p-22 - if (LIBC_UNLIKELY(x_u < 0x3D00U)) { - float delta = xf - 1.0f; - float sqrt_2_delta = fputil::sqrt<float>(2.0 * delta); - float pe = fputil::polyeval(delta, 0x1p+0f, -0x1.555556p-4f, 0x1.333334p-6f, - -0x1.6db6dcp-8f, 0x1.f1c71cp-10f); - float approx = sqrt_2_delta * pe; - return fputil::cast<float16>(approx); - } - - // acosh(x) = log(x + sqrt(x^2 - 1)) - float sqrt_term = fputil::sqrt<float>(fputil::multiply_add(xf, xf, -1.0f)); - float result = static_cast<float>(log_eval(xf + sqrt_term)); - - return fputil::cast<float16>(result); -} +LLVM_LIBC_FUNCTION(float16, acoshf16, (float16 x)) { return math::acoshf16(x); } } // namespace LIBC_NAMESPACE_DECL |