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//===-- Common header for helpers to set exceptional values -----*- C++ -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_LIBC_SRC_SUPPORT_FPUTIL_EXCEPT_VALUE_UTILS_H
#define LLVM_LIBC_SRC_SUPPORT_FPUTIL_EXCEPT_VALUE_UTILS_H
#include "FEnvImpl.h"
#include "FPBits.h"
#include "src/__support/CPP/optional.h"
#include "src/__support/macros/optimization.h" // LIBC_UNLIKELY
namespace __llvm_libc {
namespace fputil {
// This file contains utility functions and classes to manage exceptional values
// when there are many of them.
//
// Example usage:
//
// Define list of exceptional inputs and outputs:
// static constexpr int N = ...; // Number of exceptional values.
// static constexpr fputil::ExceptValues<UIntType, N> Excepts {
// <list of input bits, output bits and offsets>
// };
//
// Check for exceptional inputs:
// if (auto r = Excepts.lookup(x_bits); LIBC_UNLIKELY(r.has_value()))
// return r.value();
template <typename T, size_t N> struct ExceptValues {
static_assert(cpp::is_floating_point_v<T>, "Must be a floating point type.");
using UIntType = typename FPBits<T>::UIntType;
struct Mapping {
UIntType input;
UIntType rnd_towardzero_result;
UIntType rnd_upward_offset;
UIntType rnd_downward_offset;
UIntType rnd_tonearest_offset;
};
Mapping values[N];
LIBC_INLINE constexpr cpp::optional<T> lookup(UIntType x_bits) const {
for (size_t i = 0; i < N; ++i) {
if (LIBC_UNLIKELY(x_bits == values[i].input)) {
UIntType out_bits = values[i].rnd_towardzero_result;
switch (fputil::get_round()) {
case FE_UPWARD:
out_bits += values[i].rnd_upward_offset;
break;
case FE_DOWNWARD:
out_bits += values[i].rnd_downward_offset;
break;
case FE_TONEAREST:
out_bits += values[i].rnd_tonearest_offset;
break;
}
return FPBits<T>(out_bits).get_val();
}
}
return cpp::nullopt;
}
LIBC_INLINE constexpr cpp::optional<T> lookup_odd(UIntType x_abs,
bool sign) const {
for (size_t i = 0; i < N; ++i) {
if (LIBC_UNLIKELY(x_abs == values[i].input)) {
UIntType out_bits = values[i].rnd_towardzero_result;
switch (fputil::get_round()) {
case FE_UPWARD:
out_bits += sign ? values[i].rnd_downward_offset
: values[i].rnd_upward_offset;
break;
case FE_DOWNWARD:
out_bits += sign ? values[i].rnd_upward_offset
: values[i].rnd_downward_offset;
break;
case FE_TONEAREST:
out_bits += values[i].rnd_tonearest_offset;
break;
}
T result = FPBits<T>(out_bits).get_val();
if (sign)
result = -result;
return result;
}
}
return cpp::nullopt;
}
};
// Helper functions to set results for exceptional cases.
LIBC_INLINE float round_result_slightly_down(float value_rn) {
volatile float tmp = value_rn;
tmp = tmp - 0x1.0p-100f;
return tmp;
}
LIBC_INLINE float round_result_slightly_up(float value_rn) {
volatile float tmp = value_rn;
tmp = tmp + 0x1.0p-100f;
return tmp;
}
} // namespace fputil
} // namespace __llvm_libc
#endif // LLVM_LIBC_SRC_SUPPORT_FPUTIL_EXCEPT_VALUE_UTILS_H
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