1 //===- llvm/ADT/SmallVector.cpp - 'Normally small' vectors ----------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements the SmallVector class.
10 //
11 //===----------------------------------------------------------------------===//
12
13 // ATen: modified from llvm::SmallVector.
14 // replaced llvm::safe_malloc with std::bad_alloc
15 // deleted LLVM_ENABLE_EXCEPTIONS
16
17 #include <c10/util/SmallVector.h>
18 #include <cstdint>
19 #include <stdexcept>
20 #include <string>
21 using namespace c10;
22
23 // Check that no bytes are wasted and everything is well-aligned.
24 namespace {
25 // These structures may cause binary compat warnings on AIX. Suppress the
26 // warning since we are only using these types for the static assertions below.
27 #if defined(_AIX)
28 #pragma GCC diagnostic push
29 #pragma GCC diagnostic ignored "-Waix-compat"
30 #endif
31 struct Struct16B {
32 alignas(16) void* X;
33 };
34 struct Struct32B {
35 alignas(32) void* X;
36 };
37 #if defined(_AIX)
38 #pragma GCC diagnostic pop
39 #endif
40 } // namespace
41 static_assert(
42 sizeof(SmallVector<void*, 0>) == sizeof(unsigned) * 2 + sizeof(void*),
43 "wasted space in SmallVector size 0");
44 static_assert(
45 alignof(SmallVector<Struct16B, 0>) >= alignof(Struct16B),
46 "wrong alignment for 16-byte aligned T");
47 static_assert(
48 alignof(SmallVector<Struct32B, 0>) >= alignof(Struct32B),
49 "wrong alignment for 32-byte aligned T");
50 static_assert(
51 sizeof(SmallVector<Struct16B, 0>) >= alignof(Struct16B),
52 "missing padding for 16-byte aligned T");
53 static_assert(
54 sizeof(SmallVector<Struct32B, 0>) >= alignof(Struct32B),
55 "missing padding for 32-byte aligned T");
56 static_assert(
57 sizeof(SmallVector<void*, 1>) == sizeof(unsigned) * 2 + sizeof(void*) * 2,
58 "wasted space in SmallVector size 1");
59
60 static_assert(
61 sizeof(SmallVector<char, 0>) == sizeof(void*) * 2 + sizeof(void*),
62 "1 byte elements have word-sized type for size and capacity");
63
64 /// Report that MinSize doesn't fit into this vector's size type. Throws
65 /// std::length_error or calls report_fatal_error.
66 [[noreturn]] static void report_size_overflow(size_t MinSize, size_t MaxSize);
report_size_overflow(size_t MinSize,size_t MaxSize)67 static void report_size_overflow(size_t MinSize, size_t MaxSize) {
68 std::string Reason = "SmallVector unable to grow. Requested capacity (" +
69 std::to_string(MinSize) +
70 ") is larger than maximum value for size type (" +
71 std::to_string(MaxSize) + ")";
72 throw std::length_error(Reason);
73 }
74
75 /// Report that this vector is already at maximum capacity. Throws
76 /// std::length_error or calls report_fatal_error.
77 [[noreturn]] static void report_at_maximum_capacity(size_t MaxSize);
report_at_maximum_capacity(size_t MaxSize)78 static void report_at_maximum_capacity(size_t MaxSize) {
79 std::string Reason =
80 "SmallVector capacity unable to grow. Already at maximum size " +
81 std::to_string(MaxSize);
82 throw std::length_error(Reason);
83 }
84
85 // Note: Moving this function into the header may cause performance regression.
86 template <class Size_T>
getNewCapacity(size_t MinSize,size_t TSize,size_t OldCapacity)87 static size_t getNewCapacity(size_t MinSize, size_t TSize, size_t OldCapacity) {
88 constexpr size_t MaxSize = std::numeric_limits<Size_T>::max();
89
90 // Ensure we can fit the new capacity.
91 // This is only going to be applicable when the capacity is 32 bit.
92 if (MinSize > MaxSize)
93 report_size_overflow(MinSize, MaxSize);
94
95 // Ensure we can meet the guarantee of space for at least one more element.
96 // The above check alone will not catch the case where grow is called with a
97 // default MinSize of 0, but the current capacity cannot be increased.
98 // This is only going to be applicable when the capacity is 32 bit.
99 if (OldCapacity == MaxSize)
100 report_at_maximum_capacity(MaxSize);
101
102 // In theory 2*capacity can overflow if the capacity is 64 bit, but the
103 // original capacity would never be large enough for this to be a problem.
104 size_t NewCapacity = 2 * OldCapacity + 1; // Always grow.
105 return std::min(std::max(NewCapacity, MinSize), MaxSize);
106 }
107
108 // Note: Moving this function into the header may cause performance regression.
109 template <class Size_T>
mallocForGrow(size_t MinSize,size_t TSize,size_t & NewCapacity)110 void* SmallVectorBase<Size_T>::mallocForGrow(
111 size_t MinSize,
112 size_t TSize,
113 size_t& NewCapacity) {
114 NewCapacity = getNewCapacity<Size_T>(MinSize, TSize, this->capacity());
115 // NOLINTNEXTLINE(cppcoreguidelines-no-malloc)
116 auto Result = std::malloc(NewCapacity * TSize);
117 if (Result == nullptr) {
118 throw std::bad_alloc();
119 }
120 return Result;
121 }
122
123 // Note: Moving this function into the header may cause performance regression.
124 template <class Size_T>
grow_pod(const void * FirstEl,size_t MinSize,size_t TSize)125 void SmallVectorBase<Size_T>::grow_pod(
126 const void* FirstEl,
127 size_t MinSize,
128 size_t TSize) {
129 size_t NewCapacity = getNewCapacity<Size_T>(MinSize, TSize, this->capacity());
130 void* NewElts = nullptr;
131 if (BeginX == FirstEl) {
132 // NOLINTNEXTLINE(cppcoreguidelines-no-malloc)
133 NewElts = std::malloc(NewCapacity * TSize);
134 if (NewElts == nullptr) {
135 throw std::bad_alloc();
136 }
137
138 // Copy the elements over. No need to run dtors on PODs.
139 memcpy(NewElts, this->BeginX, size() * TSize);
140 } else {
141 // If this wasn't grown from the inline copy, grow the allocated space.
142 // NOLINTNEXTLINE(cppcoreguidelines-no-malloc)
143 NewElts = std::realloc(this->BeginX, NewCapacity * TSize);
144 if (NewElts == nullptr) {
145 throw std::bad_alloc();
146 }
147 }
148
149 this->BeginX = NewElts;
150 this->Capacity = NewCapacity;
151 }
152
153 template class c10::SmallVectorBase<uint32_t>;
154
155 // Disable the uint64_t instantiation for 32-bit builds.
156 // Both uint32_t and uint64_t instantiations are needed for 64-bit builds.
157 // This instantiation will never be used in 32-bit builds, and will cause
158 // warnings when sizeof(Size_T) > sizeof(size_t).
159 #if SIZE_MAX > UINT32_MAX
160 template class c10::SmallVectorBase<uint64_t>;
161
162 // Assertions to ensure this #if stays in sync with SmallVectorSizeType.
163 static_assert(
164 sizeof(SmallVectorSizeType<char>) == sizeof(uint64_t),
165 "Expected SmallVectorBase<uint64_t> variant to be in use.");
166 #else
167 static_assert(
168 sizeof(SmallVectorSizeType<char>) == sizeof(uint32_t),
169 "Expected SmallVectorBase<uint32_t> variant to be in use.");
170 #endif
171