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//===-- Utilities for double-double data type. ------------------*- 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_DOUBLEDOUBLE_H
#define LLVM_LIBC_SRC_SUPPORT_FPUTIL_DOUBLEDOUBLE_H
#include "multiply_add.h"
#include "src/__support/common.h"
#include "src/__support/number_pair.h"
namespace __llvm_libc::fputil {
using DoubleDouble = __llvm_libc::NumberPair<double>;
// Assumption: |a| >= |b|
LIBC_INLINE constexpr DoubleDouble exact_add(double a, double b) {
DoubleDouble r{0.0, 0.0};
r.hi = a + b;
double t = r.hi - a;
r.lo = b - t;
return r;
}
// Assumption: |a.hi| >= |b.hi|
LIBC_INLINE constexpr DoubleDouble add(DoubleDouble a, DoubleDouble b) {
DoubleDouble r = exact_add(a.hi, b.hi);
double lo = a.lo + b.lo;
return exact_add(r.hi, r.lo + lo);
}
// Assumption: |a.hi| >= |b|
LIBC_INLINE constexpr DoubleDouble add(DoubleDouble a, double b) {
DoubleDouble r = exact_add(a.hi, b);
return exact_add(r.hi, r.lo + a.lo);
}
// TODO(lntue): add a correct multiplication when FMA instructions are not
// available.
LIBC_INLINE DoubleDouble exact_mult(double a, double b) {
DoubleDouble r{0.0, 0.0};
r.hi = a * b;
r.lo = fputil::multiply_add(a, b, -r.hi);
return r;
}
} // namespace __llvm_libc::fputil
#endif // LLVM_LIBC_SRC_SUPPORT_FPUTIL_DOUBLEDOUBLE_H
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