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#include "llvm/ADT/SmallVector.h"
14#include "llvm/ADT/Twine.h"
15#include "llvm/Support/MemAlloc.h"
16#include <cstdint>
17#ifdef LLVM_ENABLE_EXCEPTIONS
18#include <stdexcept>
19#endif
20using namespace llvm;
21
22// Check that no bytes are wasted and everything is well-aligned.
23namespace {
24// These structures may cause binary compat warnings on AIX. Suppress the
25// warning since we are only using these types for the static assertions below.
26#if defined(_AIX)
27#pragma GCC diagnostic push
28#pragma GCC diagnostic ignored "-Waix-compat"
29#endif
30struct Struct16B {
31 alignas(16) void *X;
32};
33struct Struct32B {
34 alignas(32) void *X;
35};
36#if defined(_AIX)
37#pragma GCC diagnostic pop
38#endif
39}
40static_assert(sizeof(SmallVector<void *, 0>) ==
41 sizeof(unsigned) * 2 + sizeof(void *),
42 "wasted space in SmallVector size 0");
43static_assert(alignof(SmallVector<Struct16B, 0>) >= alignof(Struct16B),
44 "wrong alignment for 16-byte aligned T");
45static_assert(alignof(SmallVector<Struct32B, 0>) >= alignof(Struct32B),
46 "wrong alignment for 32-byte aligned T");
47static_assert(sizeof(SmallVector<Struct16B, 0>) >= alignof(Struct16B),
48 "missing padding for 16-byte aligned T");
49static_assert(sizeof(SmallVector<Struct32B, 0>) >= alignof(Struct32B),
50 "missing padding for 32-byte aligned T");
51static_assert(sizeof(SmallVector<void *, 1>) ==
52 sizeof(unsigned) * 2 + sizeof(void *) * 2,
53 "wasted space in SmallVector size 1");
54
55static_assert(sizeof(SmallVector<char, 0>) ==
56 sizeof(void *) * 2 + sizeof(void *),
57 "1 byte elements have word-sized type for size and capacity");
58
59/// Report that MinSize doesn't fit into this vector's size type. Throws
60/// std::length_error or calls report_fatal_error.
61[[noreturn]] static void report_size_overflow(size_t MinSize, size_t MaxSize);
62static void report_size_overflow(size_t MinSize, size_t MaxSize) {
63 std::string Reason = "SmallVector unable to grow. Requested capacity (" +
64 std::to_string(val: MinSize) +
65 ") is larger than maximum value for size type (" +
66 std::to_string(val: MaxSize) + ")";
67#ifdef LLVM_ENABLE_EXCEPTIONS
68 throw std::length_error(Reason);
69#else
70 report_fatal_error(reason: Twine(Reason));
71#endif
72}
73
74/// Report that this vector is already at maximum capacity. Throws
75/// std::length_error or calls report_fatal_error.
76[[noreturn]] static void report_at_maximum_capacity(size_t MaxSize);
77static void report_at_maximum_capacity(size_t MaxSize) {
78 std::string Reason =
79 "SmallVector capacity unable to grow. Already at maximum size " +
80 std::to_string(val: MaxSize);
81#ifdef LLVM_ENABLE_EXCEPTIONS
82 throw std::length_error(Reason);
83#else
84 report_fatal_error(reason: Twine(Reason));
85#endif
86}
87
88// Note: Moving this function into the header may cause performance regression.
89template <class Size_T>
90static size_t getNewCapacity(size_t MinSize, size_t TSize, size_t OldCapacity) {
91 constexpr size_t MaxSize = std::numeric_limits<Size_T>::max();
92
93 // Ensure we can fit the new capacity.
94 // This is only going to be applicable when the capacity is 32 bit.
95 if (MinSize > MaxSize)
96 report_size_overflow(MinSize, MaxSize);
97
98 // Ensure we can meet the guarantee of space for at least one more element.
99 // The above check alone will not catch the case where grow is called with a
100 // default MinSize of 0, but the current capacity cannot be increased.
101 // This is only going to be applicable when the capacity is 32 bit.
102 if (OldCapacity == MaxSize)
103 report_at_maximum_capacity(MaxSize);
104
105 // In theory 2*capacity can overflow if the capacity is 64 bit, but the
106 // original capacity would never be large enough for this to be a problem.
107 size_t NewCapacity = 2 * OldCapacity + 1; // Always grow.
108 return std::clamp(val: NewCapacity, lo: MinSize, hi: MaxSize);
109}
110
111/// If vector was first created with capacity 0, getFirstEl() points to the
112/// memory right after, an area unallocated. If a subsequent allocation,
113/// that grows the vector, happens to return the same pointer as getFirstEl(),
114/// get a new allocation, otherwise isSmall() will falsely return that no
115/// allocation was done (true) and the memory will not be freed in the
116/// destructor. If a VSize is given (vector size), also copy that many
117/// elements to the new allocation - used if realloca fails to increase
118/// space, and happens to allocate precisely at BeginX.
119/// This is unlikely to be called often, but resolves a memory leak when the
120/// situation does occur.
121static void *replaceAllocation(void *NewElts, size_t TSize, size_t NewCapacity,
122 size_t VSize = 0) {
123 void *NewEltsReplace = llvm::safe_malloc(Sz: NewCapacity * TSize);
124 if (VSize)
125 memcpy(dest: NewEltsReplace, src: NewElts, n: VSize * TSize);
126 free(ptr: NewElts);
127 return NewEltsReplace;
128}
129
130// Note: Moving this function into the header may cause performance regression.
131template <class Size_T>
132void *SmallVectorBase<Size_T>::mallocForGrow(void *FirstEl, size_t MinSize,
133 size_t TSize,
134 size_t &NewCapacity) {
135 NewCapacity = getNewCapacity<Size_T>(MinSize, TSize, this->capacity());
136 // Even if capacity is not 0 now, if the vector was originally created with
137 // capacity 0, it's possible for the malloc to return FirstEl.
138 void *NewElts = llvm::safe_malloc(Sz: NewCapacity * TSize);
139 if (NewElts == FirstEl)
140 NewElts = replaceAllocation(NewElts, TSize, NewCapacity);
141 return NewElts;
142}
143
144// Note: Moving this function into the header may cause performance regression.
145template <class Size_T>
146void SmallVectorBase<Size_T>::grow_pod(void *FirstEl, size_t MinSize,
147 size_t TSize) {
148 size_t NewCapacity = getNewCapacity<Size_T>(MinSize, TSize, this->capacity());
149 void *NewElts;
150 if (BeginX == FirstEl) {
151 NewElts = llvm::safe_malloc(Sz: NewCapacity * TSize);
152 if (NewElts == FirstEl)
153 NewElts = replaceAllocation(NewElts, TSize, NewCapacity);
154
155 // Copy the elements over. No need to run dtors on PODs.
156 memcpy(NewElts, this->BeginX, size() * TSize);
157 } else {
158 // If this wasn't grown from the inline copy, grow the allocated space.
159 NewElts = llvm::safe_realloc(Ptr: this->BeginX, Sz: NewCapacity * TSize);
160 if (NewElts == FirstEl)
161 NewElts = replaceAllocation(NewElts, TSize, NewCapacity, size());
162 }
163
164 this->set_allocation_range(NewElts, NewCapacity);
165}
166
167template class llvm::SmallVectorBase<uint32_t>;
168
169// Disable the uint64_t instantiation for 32-bit builds.
170// Both uint32_t and uint64_t instantiations are needed for 64-bit builds.
171// This instantiation will never be used in 32-bit builds, and will cause
172// warnings when sizeof(Size_T) > sizeof(size_t).
173#if SIZE_MAX > UINT32_MAX
174template class llvm::SmallVectorBase<uint64_t>;
175
176// Assertions to ensure this #if stays in sync with SmallVectorSizeType.
177static_assert(sizeof(SmallVectorSizeType<char>) == sizeof(uint64_t),
178 "Expected SmallVectorBase<uint64_t> variant to be in use.");
179#else
180static_assert(sizeof(SmallVectorSizeType<char>) == sizeof(uint32_t),
181 "Expected SmallVectorBase<uint32_t> variant to be in use.");
182#endif
183