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[libc][NFC] Use cpp::optional for checking exceptional values of math functions.
Update the utility functions for checking exceptional values of math functions to use cpp::optional return values. Reviewed By: sivachandra Differential Revision: https://reviews.llvm.org/D133134
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@ -102,6 +102,7 @@ add_header_library(
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DEPENDS
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.fp_bits
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.fenv_impl
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libc.src.__support.CPP.optional
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)
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@ -11,55 +11,88 @@
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#include "FEnvImpl.h"
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#include "FPBits.h"
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#include "src/__support/CPP/optional.h"
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namespace __llvm_libc {
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namespace fputil {
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template <typename T, int N> struct ExceptionalValues {
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using UIntType = typename FPBits<T>::UIntType;
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static constexpr int SIZE = N;
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// Input bits.
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UIntType inputs[SIZE];
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// Output bits contains 4 values:
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// output[i][0]: output bits corresponding to FE_TOWARDZERO
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// output[i][1]: offset for FE_UPWARD
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// output[i][2]: offset for FE_DOWNWARD
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// output[i][3]: offset for FE_TONEAREST
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UIntType outputs[SIZE][4];
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};
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// This file contains utility functions and classes to manage exceptional values
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// when there are many of them.
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//
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// Example usage:
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//
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// Define list of exceptional inputs and outputs:
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// static constexpr int N = ...; // Number of exceptional values.
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// static constexpr fputil::ExceptValues<UIntType, N> Excepts {
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// <list of input bits, output bits and offsets>
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// };
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//
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// Check for exceptional inputs:
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// if (auto r = Excepts.lookup(x_bits); unlikely(r.has_value()))
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// return r.value();
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template <typename T, int N> struct ExceptionChecker {
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using UIntType = typename FPBits<T>::UIntType;
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using FPBits = FPBits<T>;
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using ExceptionalValues = ExceptionalValues<T, N>;
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template <typename T, size_t N> struct ExceptValues {
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static_assert(cpp::is_floating_point_v<T>, "Must be a floating point type.");
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static bool check_odd_func(const ExceptionalValues &ExceptVals,
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UIntType x_abs, bool sign, T &result) {
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for (int i = 0; i < N; ++i) {
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if (unlikely(x_abs == ExceptVals.inputs[i])) {
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UIntType out_bits = ExceptVals.outputs[i][0]; // FE_TOWARDZERO
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using UIntType = typename FPBits<T>::UIntType;
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struct Mapping {
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UIntType input;
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UIntType rnd_towardzero_result;
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UIntType rnd_upward_offset;
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UIntType rnd_downward_offset;
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UIntType rnd_tonearest_offset;
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};
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Mapping values[N];
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constexpr cpp::optional<T> lookup(UIntType x_bits) const {
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for (size_t i = 0; i < N; ++i) {
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if (unlikely(x_bits == values[i].input)) {
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UIntType out_bits = values[i].rnd_towardzero_result;
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switch (fputil::get_round()) {
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case FE_UPWARD:
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out_bits +=
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sign ? ExceptVals.outputs[i][2] : ExceptVals.outputs[i][1];
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out_bits += values[i].rnd_upward_offset;
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break;
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case FE_DOWNWARD:
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out_bits +=
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sign ? ExceptVals.outputs[i][1] : ExceptVals.outputs[i][2];
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out_bits += values[i].rnd_downward_offset;
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break;
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case FE_TONEAREST:
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out_bits += ExceptVals.outputs[i][3];
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out_bits += values[i].rnd_tonearest_offset;
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break;
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}
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result = FPBits(out_bits).get_val();
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return FPBits<T>(out_bits).get_val();
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}
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}
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return cpp::nullopt;
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}
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constexpr cpp::optional<T> lookup_odd(UIntType x_abs, bool sign) const {
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for (size_t i = 0; i < N; ++i) {
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if (unlikely(x_abs == values[i].input)) {
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UIntType out_bits = values[i].rnd_towardzero_result;
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switch (fputil::get_round()) {
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case FE_UPWARD:
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out_bits += sign ? values[i].rnd_downward_offset
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: values[i].rnd_upward_offset;
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break;
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case FE_DOWNWARD:
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out_bits += sign ? values[i].rnd_upward_offset
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: values[i].rnd_downward_offset;
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break;
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case FE_TONEAREST:
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out_bits += values[i].rnd_tonearest_offset;
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break;
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}
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T result = FPBits<T>(out_bits).get_val();
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if (sign)
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result = -result;
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return true;
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return result;
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}
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}
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return false;
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return cpp::nullopt;
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}
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};
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@ -20,27 +20,23 @@
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namespace __llvm_libc {
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// Exceptional cases for cosf.
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static constexpr int COSF_EXCEPTS = 6;
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static constexpr size_t N_EXCEPTS = 6;
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static constexpr fputil::ExceptionalValues<float, COSF_EXCEPTS> CosfExcepts{
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/* inputs */ {
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0x55325019, // x = 0x1.64a032p43
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0x5922aa80, // x = 0x1.4555p51
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0x5aa4542c, // x = 0x1.48a858p54
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0x5f18b878, // x = 0x1.3170fp63
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0x6115cb11, // x = 0x1.2b9622p67
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0x7beef5ef, // x = 0x1.ddebdep120
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},
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/* outputs (RZ, RU offset, RD offset, RN offset) */
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{
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{0x3f4ea5d2, 1, 0, 0}, // x = 0x1.64a032p43, cos(x) = 0x1.9d4ba4p-1 (RZ)
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{0x3f08aebe, 1, 0, 1}, // x = 0x1.4555p51, cos(x) = 0x1.115d7cp-1 (RZ)
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{0x3efa40a4, 1, 0, 0}, // x = 0x1.48a858p54, cos(x) = 0x1.f48148p-2 (RZ)
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{0x3f7f14bb, 1, 0, 0}, // x = 0x1.3170fp63, cos(x) = 0x1.fe2976p-1 (RZ)
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{0x3f78142e, 1, 0, 1}, // x = 0x1.2b9622p67, cos(x) = 0x1.f0285cp-1 (RZ)
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{0x3f08a21c, 1, 0,
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0}, // x = 0x1.ddebdep120, cos(x) = 0x1.114438p-1 (RZ)
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}};
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static constexpr fputil::ExceptValues<float, N_EXCEPTS> COSF_EXCEPTS{{
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// (inputs, RZ output, RU offset, RD offset, RN offset)
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// x = 0x1.64a032p43, cos(x) = 0x1.9d4ba4p-1 (RZ)
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{0x55325019, 0x3f4ea5d2, 1, 0, 0},
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// x = 0x1.4555p51, cos(x) = 0x1.115d7cp-1 (RZ)
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{0x5922aa80, 0x3f08aebe, 1, 0, 1},
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// x = 0x1.48a858p54, cos(x) = 0x1.f48148p-2 (RZ)
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{0x5aa4542c, 0x3efa40a4, 1, 0, 0},
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// x = 0x1.3170fp63, cos(x) = 0x1.fe2976p-1 (RZ)
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{0x5f18b878, 0x3f7f14bb, 1, 0, 0},
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// x = 0x1.2b9622p67, cos(x) = 0x1.f0285cp-1 (RZ)
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{0x6115cb11, 0x3f78142e, 1, 0, 1},
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// x = 0x1.ddebdep120, cos(x) = 0x1.114438p-1 (RZ)
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{0x7beef5ef, 0x3f08a21c, 1, 0, 0},
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}};
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LLVM_LIBC_FUNCTION(float, cosf, (float x)) {
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using FPBits = typename fputil::FPBits<float>;
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@ -110,12 +106,8 @@ LLVM_LIBC_FUNCTION(float, cosf, (float x)) {
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#endif // LIBC_TARGET_HAS_FMA
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}
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using ExceptChecker = typename fputil::ExceptionChecker<float, COSF_EXCEPTS>;
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{
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float result;
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if (ExceptChecker::check_odd_func(CosfExcepts, x_abs, false, result))
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return result;
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}
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if (auto r = COSF_EXCEPTS.lookup(x_abs); unlikely(r.has_value()))
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return r.value();
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// x is inf or nan.
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if (unlikely(x_abs >= 0x7f80'0000U)) {
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@ -56,29 +56,23 @@ static constexpr double TAN_K_PI_OVER_32[32] = {
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};
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// Exceptional cases for tanf.
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static constexpr int TANF_EXCEPTS = 6;
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static constexpr size_t N_EXCEPTS = 6;
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static constexpr fputil::ExceptionalValues<float, TANF_EXCEPTS> TanfExcepts{
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/* inputs */ {
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0x531d744c, // x = 0x1.3ae898p39
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0x57d7b0ed, // x = 0x1.af61dap48
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0x65ee8695, // x = 0x1.dd0d2ap76
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0x6798fe4f, // x = 0x1.31fc9ep80
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0x6ad36709, // x = 0x1.a6ce12p86
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0x72b505bb, // x = 0x1.6a0b76p102
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},
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/* outputs (RZ, RU offset, RD offset, RN offset) */
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{
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{0x4591ea1e, 1, 0, 1}, // x = 0x1.3ae898p39, tan(x) = 0x1.23d43cp12 (RZ)
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{0x3eb068e3, 1, 0, 1}, // x = 0x1.af61dap48, tan(x) = 0x1.60d1c6p-2 (RZ)
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{0xcaa32f8e, 0, 1,
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0}, // x = 0x1.dd0d2ap76, tan(x) = -0x1.465f1cp22 (RZ)
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{0x461e09f7, 1, 0, 0}, // x = 0x1.31fc9ep80, tan(x) = 0x1.3c13eep13 (RZ)
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{0xbf62b097, 0, 1,
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0}, // x = 0x1.a6ce12p86, tan(x) = -0x1.c5612ep-1 (RZ)
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{0xbff2150f, 0, 1,
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0}, // x = 0x1.6a0b76p102, tan(x) = -0x1.e42a1ep0 (RZ)
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}};
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static constexpr fputil::ExceptValues<float, N_EXCEPTS> TANF_EXCEPTS{{
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// (inputs, RZ output, RU offset, RD offset, RN offset)
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// x = 0x1.3ae898p39, tan(x) = 0x1.23d43cp12 (RZ)
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{0x531d744c, 0x4591ea1e, 1, 0, 1},
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// x = 0x1.af61dap48, tan(x) = 0x1.60d1c6p-2 (RZ)
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{0x57d7b0ed, 0x3eb068e3, 1, 0, 1},
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// x = 0x1.dd0d2ap76, tan(x) = -0x1.465f1cp22 (RZ)
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{0x65ee8695, 0xcaa32f8e, 0, 1, 0},
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// x = 0x1.31fc9ep80, tan(x) = 0x1.3c13eep13 (RZ)
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{0x6798fe4f, 0x461e09f7, 1, 0, 0},
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// x = 0x1.a6ce12p86, tan(x) = -0x1.c5612ep-1 (RZ)
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{0x6ad36709, 0xbf62b097, 0, 1, 0},
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// x = 0x1.6a0b76p102, tan(x) = -0x1.e42a1ep0 (RZ)
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{0x72b505bb, 0xbff2150f, 0, 1, 0},
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}};
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LLVM_LIBC_FUNCTION(float, tanf, (float x)) {
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using FPBits = typename fputil::FPBits<float>;
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@ -200,14 +194,9 @@ LLVM_LIBC_FUNCTION(float, tanf, (float x)) {
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k = small_range_reduction(xd, y);
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} else {
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using ExceptChecker =
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typename fputil::ExceptionChecker<float, TANF_EXCEPTS>;
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{
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float result;
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if (ExceptChecker::check_odd_func(TanfExcepts, x_abs, x_sign <= 0.0,
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result))
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return result;
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}
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if (auto r = TANF_EXCEPTS.lookup_odd(x_abs, x_sign <= 0.0);
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unlikely(r.has_value()))
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return r.value();
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fputil::FPBits<float> x_bits(x_abs);
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k = large_range_reduction(xd, x_bits.get_exponent(), y);
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