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//===-- lib/Evaluate/int-power.h --------------------------------*- 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 FORTRAN_EVALUATE_INT_POWER_H_
#define FORTRAN_EVALUATE_INT_POWER_H_
// Computes an integer power of a real or complex value.
#include "flang/Evaluate/target.h"
namespace Fortran::evaluate {
template <typename REAL, typename INT>
ValueWithRealFlags<REAL> TimesIntPowerOf(const REAL &factor, const REAL &base,
const INT &power,
Rounding rounding = TargetCharacteristics::defaultRounding) {
ValueWithRealFlags<REAL> result{factor};
if (base.IsNotANumber()) {
result.value = REAL::NotANumber();
result.flags.set(RealFlag::InvalidArgument);
} else if (power.IsZero()) {
if (base.IsZero() || base.IsInfinite()) {
result.flags.set(RealFlag::InvalidArgument);
}
} else {
bool negativePower{power.IsNegative()};
INT absPower{power.ABS().value};
REAL squares{base};
int nbits{INT::bits - absPower.LEADZ()};
for (int j{0}; j < nbits; ++j) {
if (j > 0) { // avoid spurious overflow on last iteration
squares =
squares.Multiply(squares, rounding).AccumulateFlags(result.flags);
}
if (absPower.BTEST(j)) {
if (negativePower) {
result.value = result.value.Divide(squares, rounding)
.AccumulateFlags(result.flags);
} else {
result.value = result.value.Multiply(squares, rounding)
.AccumulateFlags(result.flags);
}
}
}
}
return result;
}
template <typename REAL, typename INT>
ValueWithRealFlags<REAL> IntPower(const REAL &base, const INT &power,
Rounding rounding = TargetCharacteristics::defaultRounding) {
REAL one{REAL::FromInteger(INT{1}).value};
return TimesIntPowerOf(one, base, power, rounding);
}
} // namespace Fortran::evaluate
#endif // FORTRAN_EVALUATE_INT_POWER_H_
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