9dd6f0d089
MSVC 2015 and 2017 implement std::is_trivially_copyable, but not correctly. Hence, reimplement it using more low-level primitives. For stdlibc++ versions below 5.0, we already have a workaround for the missing support of std::is_trivially_copyable, but this is an unsound approximation, because it is ignoring move constructor, move assignment and copy assignment. Therefore, do not use this approximation for asserting trivial copyability of a type. Finally, add unittests for the new is_trivially_copyable implementations. R=mstarzinger@chromium.org CC=loorongjie@gmail.com Change-Id: I9ee56a65882e8c94b72c9a2d484edd27963a5d89 Reviewed-on: https://chromium-review.googlesource.com/941521 Reviewed-by: Michael Starzinger <mstarzinger@chromium.org> Commit-Queue: Clemens Hammacher <clemensh@chromium.org> Cr-Commit-Position: refs/heads/master@{#51651}
99 lines
3.2 KiB
C++
99 lines
3.2 KiB
C++
// Copyright 2017 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef V8_BOXED_FLOAT_H_
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#define V8_BOXED_FLOAT_H_
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#include <cmath>
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#include "src/base/macros.h"
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#include "src/globals.h"
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namespace v8 {
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namespace internal {
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// TODO(ahaas): Make these classes with the one in double.h
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// Safety wrapper for a 32-bit floating-point value to make sure we don't lose
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// the exact bit pattern during deoptimization when passing this value.
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class Float32 {
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public:
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Float32() = default;
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// This constructor does not guarantee that bit pattern of the input value
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// is preserved if the input is a NaN.
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explicit Float32(float value) : bit_pattern_(bit_cast<uint32_t>(value)) {
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// Check that the provided value is not a NaN, because the bit pattern of a
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// NaN may be changed by a bit_cast, e.g. for signalling NaNs on ia32.
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DCHECK(!std::isnan(value));
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}
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uint32_t get_bits() const { return bit_pattern_; }
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float get_scalar() const { return bit_cast<float>(bit_pattern_); }
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bool is_nan() const {
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// Even though {get_scalar()} might flip the quiet NaN bit, it's ok here,
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// because this does not change the is_nan property.
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return std::isnan(get_scalar());
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}
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// Return a pointer to the field storing the bit pattern. Used in code
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// generation tests to store generated values there directly.
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uint32_t* get_bits_address() { return &bit_pattern_; }
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static constexpr Float32 FromBits(uint32_t bits) { return Float32(bits); }
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private:
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uint32_t bit_pattern_ = 0;
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explicit constexpr Float32(uint32_t bit_pattern)
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: bit_pattern_(bit_pattern) {}
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};
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ASSERT_TRIVIALLY_COPYABLE(Float32);
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// Safety wrapper for a 64-bit floating-point value to make sure we don't lose
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// the exact bit pattern during deoptimization when passing this value.
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// TODO(ahaas): Unify this class with Double in double.h
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class Float64 {
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public:
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Float64() = default;
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// This constructor does not guarantee that bit pattern of the input value
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// is preserved if the input is a NaN.
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explicit Float64(double value) : bit_pattern_(bit_cast<uint64_t>(value)) {
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// Check that the provided value is not a NaN, because the bit pattern of a
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// NaN may be changed by a bit_cast, e.g. for signalling NaNs on ia32.
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DCHECK(!std::isnan(value));
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}
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uint64_t get_bits() const { return bit_pattern_; }
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double get_scalar() const { return bit_cast<double>(bit_pattern_); }
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bool is_hole_nan() const { return bit_pattern_ == kHoleNanInt64; }
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bool is_nan() const {
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// Even though {get_scalar()} might flip the quiet NaN bit, it's ok here,
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// because this does not change the is_nan property.
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return std::isnan(get_scalar());
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}
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// Return a pointer to the field storing the bit pattern. Used in code
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// generation tests to store generated values there directly.
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uint64_t* get_bits_address() { return &bit_pattern_; }
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static constexpr Float64 FromBits(uint64_t bits) { return Float64(bits); }
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private:
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uint64_t bit_pattern_ = 0;
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explicit constexpr Float64(uint64_t bit_pattern)
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: bit_pattern_(bit_pattern) {}
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};
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ASSERT_TRIVIALLY_COPYABLE(Float64);
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} // namespace internal
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} // namespace v8
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#endif // V8_BOXED_FLOAT_H_
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