object-introspection/oi/OITraceCode.cpp

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/*
* Copyright (c) Meta Platforms, Inc. and affiliates.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
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#define NDEBUG 1
// Required for compatibility with new glibc headers
#define __malloc__(x, y) __malloc__
#if !__has_builtin(__builtin_free)
#define __builtin_free(x) free(x)
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#endif
#pragma clang diagnostic ignored "-Wunknown-attributes"
// clang-format off
// The header xmmintrin.h must come first. Otherwise it results in errors
// jemalloc during JIT compilation
#include <xmmintrin.h>
#include <cstdint>
#include <utility>
#include <unistd.h>
// clang-format on
#define C10_USING_CUSTOM_GENERATED_MACROS
constexpr int oidMagicId = 0x01DE8;
#include <array>
namespace {
class {
private:
// 1 MiB of pointers
std::array<uintptr_t, (1 << 20) / sizeof(uintptr_t)> data;
// twang_mix64 hash function, taken from Folly where it is used
// as the default hash function for 64-bit integers
constexpr static uint64_t twang_mix64(uint64_t key) noexcept {
key = (~key) + (key << 21); // key *= (1 << 21) - 1; key -= 1;
key = key ^ (key >> 24);
key = key + (key << 3) + (key << 8); // key *= 1 + (1 << 3) + (1 << 8)
key = key ^ (key >> 14);
key = key + (key << 2) + (key << 4); // key *= 1 + (1 << 2) + (1 << 4)
key = key ^ (key >> 28);
key = key + (key << 31); // key *= 1 + (1 << 31)
return key;
}
public:
void initialize() noexcept {
data.fill(0);
}
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// Adds the pointer to the set.
// Returns `true` if the value was newly added,
// or `false` if the value was already present.
bool add(uintptr_t pointer) noexcept {
__builtin_assume(pointer > 0);
uint64_t index = twang_mix64(pointer) % data.size();
while (true) {
uintptr_t entry = data[index];
if (entry == 0) {
data[index] = pointer;
return true;
}
if (entry == pointer) {
return false;
}
index = (index + 1) % data.size();
}
}
} static pointers;
} // namespace
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// alignas(0) is ignored according to docs so can be default
template <unsigned int N, unsigned int align = 0>
struct alignas(align) DummySizedOperator {
char c[N];
};
// The empty class specialization is, unfortunately, necessary. When this
// operator is passed as a template parameter to something like unordered_map,
// even though an empty class and a class with a single character have size one,
// there is some empty class optimization that changes the static size of the
// container if an empty class is passed.
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// DummySizedOperator<0,0> also collapses to this
template <>
struct DummySizedOperator<0> {};
template <template <typename, size_t, size_t> typename DerivedT,
typename T,
size_t N,
size_t Align>
struct DummyAllocatorBase {
using value_type = T;
T* allocate(std::size_t n) {
return nullptr;
}
void deallocate(T* p, std::size_t n) noexcept {
}
template <typename U>
struct rebind {
using other = DerivedT<U, N, Align>;
};
};
template <typename T, size_t N, size_t Align = 0>
struct alignas(Align) DummyAllocator
: DummyAllocatorBase<DummyAllocator, T, N, Align> {
char c[N];
};
template <typename T>
struct DummyAllocator<T, 0> : DummyAllocatorBase<DummyAllocator, T, 0, 0> {};
template <typename Type, size_t ExpectedSize, size_t ActualSize = 0>
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struct validate_size {
static constexpr bool value = true;
static_assert(ExpectedSize == ActualSize);
};
template <typename Type, size_t ExpectedSize>
struct validate_size<Type, ExpectedSize>
: validate_size<Type, ExpectedSize, sizeof(Type)> {};
template <size_t ExpectedOffset, size_t ActualOffset>
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struct validate_offset {
static constexpr bool value = true;
static_assert(ExpectedOffset == ActualOffset);
};