Ryan Macnak
7d5361ab02
TEST=ci Change-Id: Icb198c9d0eb11c11f9fa61f41c37c8705f68001c Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/481165 Commit-Queue: Ryan Macnak <rmacnak@google.com> Reviewed-by: Alexander Markov <alexmarkov@google.com>
80 lines
2.2 KiB
C++
80 lines
2.2 KiB
C++
// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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#ifndef RUNTIME_VM_DOUBLE_INTERNALS_H_
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#define RUNTIME_VM_DOUBLE_INTERNALS_H_
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#include "platform/utils.h"
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namespace dart {
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// We assume that doubles and uint64_t have the same endianness.
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static uint64_t double_to_uint64(double d) {
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return bit_cast<uint64_t>(d);
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}
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// Helper functions for doubles.
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class DoubleInternals {
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public:
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static constexpr int kSignificandSize = 53;
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explicit DoubleInternals(double d) : d64_(double_to_uint64(d)) {}
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// Returns the double's bit as uint64.
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uint64_t AsUint64() const { return d64_; }
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int Exponent() const {
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if (IsDenormal()) return kDenormalExponent;
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uint64_t d64 = AsUint64();
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int biased_e =
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static_cast<int>((d64 & kExponentMask) >> kPhysicalSignificandSize);
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return biased_e - kExponentBias;
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}
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uint64_t Significand() const {
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uint64_t d64 = AsUint64();
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uint64_t significand = d64 & kSignificandMask;
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if (!IsDenormal()) {
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return significand + kHiddenBit;
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} else {
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return significand;
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}
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}
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// Returns true if the double is a denormal.
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bool IsDenormal() const {
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uint64_t d64 = AsUint64();
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return (d64 & kExponentMask) == 0;
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}
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// We consider denormals not to be special.
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// Hence only Infinity and NaN are special.
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bool IsSpecial() const {
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uint64_t d64 = AsUint64();
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return (d64 & kExponentMask) == kExponentMask;
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}
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int Sign() const {
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uint64_t d64 = AsUint64();
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return (d64 & kSignMask) == 0 ? 1 : -1;
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}
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private:
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static constexpr uint64_t kSignMask = 0x8000000000000000;
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static constexpr uint64_t kExponentMask = 0x7FF0000000000000;
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static constexpr uint64_t kSignificandMask = 0x000FFFFFFFFFFFFF;
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static constexpr uint64_t kHiddenBit = 0x0010000000000000;
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static constexpr int kPhysicalSignificandSize =
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52; // Excludes the hidden bit.
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static constexpr int kExponentBias = 0x3FF + kPhysicalSignificandSize;
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static constexpr int kDenormalExponent = -kExponentBias + 1;
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const uint64_t d64_;
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};
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} // namespace dart
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#endif // RUNTIME_VM_DOUBLE_INTERNALS_H_
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