libc/utils/MPFRWrapper/MPFRUtils.cpp

//===-- Utils which wrap MPFR ---------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//

#include "MPFRUtils.h"

#include "utils/FPUtil/FPBits.h"

#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringRef.h"

#include <mpfr.h>
#include <stdint.h>
#include <string>

template <typename T> using FPBits = __llvm_libc::fputil::FPBits<T>;

namespace __llvm_libc {
namespace testing {
namespace mpfr {

class MPFRNumber {
  // A precision value which allows sufficiently large additional
  // precision even compared to quad-precision floating point values.
  static constexpr unsigned int mpfrPrecision = 128;

  mpfr_t value;

public:
  MPFRNumber() { mpfr_init2(value, mpfrPrecision); }

  // We use explicit EnableIf specializations to disallow implicit
  // conversions. Implicit conversions can potentially lead to loss of
  // precision.
  template <typename XType,
            cpp::EnableIfType<cpp::IsSame<float, XType>::Value, int> = 0>
  explicit MPFRNumber(XType x) {
    mpfr_init2(value, mpfrPrecision);
    mpfr_set_flt(value, x, MPFR_RNDN);
  }

  template <typename XType,
            cpp::EnableIfType<cpp::IsSame<double, XType>::Value, int> = 0>
  explicit MPFRNumber(XType x) {
    mpfr_init2(value, mpfrPrecision);
    mpfr_set_d(value, x, MPFR_RNDN);
  }

  template <typename XType,
            cpp::EnableIfType<cpp::IsSame<long double, XType>::Value, int> = 0>
  explicit MPFRNumber(XType x) {
    mpfr_init2(value, mpfrPrecision);
    mpfr_set_ld(value, x, MPFR_RNDN);
  }

  template <typename XType,
            cpp::EnableIfType<cpp::IsIntegral<XType>::Value, int> = 0>
  explicit MPFRNumber(XType x) {
    mpfr_init2(value, mpfrPrecision);
    mpfr_set_sj(value, x, MPFR_RNDN);
  }

  template <typename XType> MPFRNumber(XType x, const Tolerance &t) {
    mpfr_init2(value, mpfrPrecision);
    mpfr_set_zero(value, 1); // Set to positive zero.
    MPFRNumber xExponent(fputil::FPBits<XType>(x).getExponent());
    // E = 2^E
    mpfr_exp2(xExponent.value, xExponent.value, MPFR_RNDN);
    uint32_t bitMask = 1 << (t.width - 1);
    for (int n = -t.basePrecision; bitMask > 0; bitMask >>= 1) {
      --n;
      if (t.bits & bitMask) {
        // delta = -n
        MPFRNumber delta(n);

        // delta = 2^(-n)
        mpfr_exp2(delta.value, delta.value, MPFR_RNDN);

        // delta = E * 2^(-n)
        mpfr_mul(delta.value, delta.value, xExponent.value, MPFR_RNDN);

        // tolerance += delta
        mpfr_add(value, value, delta.value, MPFR_RNDN);
      }
    }
  }

  template <typename XType,
            cpp::EnableIfType<cpp::IsFloatingPointType<XType>::Value, int> = 0>
  MPFRNumber(Operation op, XType rawValue) {
    mpfr_init2(value, mpfrPrecision);
    MPFRNumber mpfrInput(rawValue);
    switch (op) {
    case Operation::Abs:
      mpfr_abs(value, mpfrInput.value, MPFR_RNDN);
      break;
    case Operation::Ceil:
      mpfr_ceil(value, mpfrInput.value);
      break;
    case Operation::Cos:
      mpfr_cos(value, mpfrInput.value, MPFR_RNDN);
      break;
    case Operation::Exp:
      mpfr_exp(value, mpfrInput.value, MPFR_RNDN);
      break;
    case Operation::Exp2:
      mpfr_exp2(value, mpfrInput.value, MPFR_RNDN);
      break;
    case Operation::Floor:
      mpfr_floor(value, mpfrInput.value);
      break;
    case Operation::Round:
      mpfr_round(value, mpfrInput.value);
      break;
    case Operation::Sin:
      mpfr_sin(value, mpfrInput.value, MPFR_RNDN);
      break;
    case Operation::Trunc:
      mpfr_trunc(value, mpfrInput.value);
      break;
    }
  }

  MPFRNumber(const MPFRNumber &other) {
    mpfr_set(value, other.value, MPFR_RNDN);
  }

  ~MPFRNumber() { mpfr_clear(value); }

  // Returns true if |other| is within the |tolerance| value of this
  // number.
  bool isEqual(const MPFRNumber &other, const MPFRNumber &tolerance) const {
    MPFRNumber difference;
    if (mpfr_cmp(value, other.value) >= 0)
      mpfr_sub(difference.value, value, other.value, MPFR_RNDN);
    else
      mpfr_sub(difference.value, other.value, value, MPFR_RNDN);

    return mpfr_lessequal_p(difference.value, tolerance.value);
  }

  std::string str() const {
    // 200 bytes should be more than sufficient to hold a 100-digit number
    // plus additional bytes for the decimal point, '-' sign etc.
    constexpr size_t printBufSize = 200;
    char buffer[printBufSize];
    mpfr_snprintf(buffer, printBufSize, "%100.50Rf", value);
    llvm::StringRef ref(buffer);
    ref = ref.trim();
    return ref.str();
  }

  // These functions are useful for debugging.
  float asFloat() const { return mpfr_get_flt(value, MPFR_RNDN); }
  double asDouble() const { return mpfr_get_d(value, MPFR_RNDN); }
  void dump(const char *msg) const { mpfr_printf("%s%.128Rf\n", msg, value); }
};

namespace internal {

template <typename T>
void MPFRMatcher<T>::explainError(testutils::StreamWrapper &OS) {
  MPFRNumber mpfrResult(operation, input);
  MPFRNumber mpfrInput(input);
  MPFRNumber mpfrMatchValue(matchValue);
  MPFRNumber mpfrToleranceValue(matchValue, tolerance);
  FPBits<T> inputBits(input);
  FPBits<T> matchBits(matchValue);
  // TODO: Call to llvm::utohexstr implicitly converts __uint128_t values to
  // uint64_t values. This can be fixed using a custom wrapper for
  // llvm::utohexstr to handle __uint128_t values correctly.
  OS << "Match value not within tolerance value of MPFR result:\n"
     << "  Input decimal: " << mpfrInput.str() << '\n'
     << "     Input bits: 0x" << llvm::utohexstr(inputBits.bitsAsUInt()) << '\n'
     << "  Match decimal: " << mpfrMatchValue.str() << '\n'
     << "     Match bits: 0x" << llvm::utohexstr(matchBits.bitsAsUInt()) << '\n'
     << "    MPFR result: " << mpfrResult.str() << '\n'
     << "Tolerance value: " << mpfrToleranceValue.str() << '\n';
}

template void MPFRMatcher<float>::explainError(testutils::StreamWrapper &);
template void MPFRMatcher<double>::explainError(testutils::StreamWrapper &);
template void
MPFRMatcher<long double>::explainError(testutils::StreamWrapper &);

template <typename T>
bool compare(Operation op, T input, T libcResult, const Tolerance &t) {
  MPFRNumber mpfrResult(op, input);
  MPFRNumber mpfrLibcResult(libcResult);
  MPFRNumber mpfrToleranceValue(libcResult, t);

  return mpfrResult.isEqual(mpfrLibcResult, mpfrToleranceValue);
};

template bool compare<float>(Operation, float, float, const Tolerance &);
template bool compare<double>(Operation, double, double, const Tolerance &);
template bool compare<long double>(Operation, long double, long double,
                                   const Tolerance &);

} // namespace internal

} // namespace mpfr
} // namespace testing
} // namespace __llvm_libc