LLVM 17.0.0git
SmallVector.cpp
Go to the documentation of this file.
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
14#include "llvm/ADT/Twine.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(MinSize) +
65 ") is larger than maximum value for size type (" +
66 std::to_string(MaxSize) + ")";
67#ifdef LLVM_ENABLE_EXCEPTIONS
68 throw std::length_error(Reason);
69#else
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(MaxSize);
81#ifdef LLVM_ENABLE_EXCEPTIONS
82 throw std::length_error(Reason);
83#else
85#endif
86}
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)
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(NewCapacity, MinSize, MaxSize);
109}
110
111template <class Size_T>
112void *SmallVectorBase<Size_T>::replaceAllocation(void *NewElts, size_t TSize,
113 size_t NewCapacity,
114 size_t VSize) {
115 void *NewEltsReplace = llvm::safe_malloc(NewCapacity * TSize);
116 if (VSize)
117 memcpy(NewEltsReplace, NewElts, VSize * TSize);
118 free(NewElts);
119 return NewEltsReplace;
120}
121
122// Note: Moving this function into the header may cause performance regression.
123template <class Size_T>
124void *SmallVectorBase<Size_T>::mallocForGrow(void *FirstEl, size_t MinSize,
125 size_t TSize,
126 size_t &NewCapacity) {
127 NewCapacity = getNewCapacity<Size_T>(MinSize, TSize, this->capacity());
128 // Even if capacity is not 0 now, if the vector was originally created with
129 // capacity 0, it's possible for the malloc to return FirstEl.
130 void *NewElts = llvm::safe_malloc(NewCapacity * TSize);
131 if (NewElts == FirstEl)
132 NewElts = replaceAllocation(NewElts, TSize, NewCapacity);
133 return NewElts;
134}
135
136// Note: Moving this function into the header may cause performance regression.
137template <class Size_T>
138void SmallVectorBase<Size_T>::grow_pod(void *FirstEl, size_t MinSize,
139 size_t TSize) {
140 size_t NewCapacity = getNewCapacity<Size_T>(MinSize, TSize, this->capacity());
141 void *NewElts;
142 if (BeginX == FirstEl) {
143 NewElts = llvm::safe_malloc(NewCapacity * TSize);
144 if (NewElts == FirstEl)
145 NewElts = replaceAllocation(NewElts, TSize, NewCapacity);
146
147 // Copy the elements over. No need to run dtors on PODs.
148 memcpy(NewElts, this->BeginX, size() * TSize);
149 } else {
150 // If this wasn't grown from the inline copy, grow the allocated space.
151 NewElts = llvm::safe_realloc(this->BeginX, NewCapacity * TSize);
152 if (NewElts == FirstEl)
153 NewElts = replaceAllocation(NewElts, TSize, NewCapacity, size());
154 }
155
156 this->BeginX = NewElts;
157 this->Capacity = NewCapacity;
158}
159
161
162// Disable the uint64_t instantiation for 32-bit builds.
163// Both uint32_t and uint64_t instantiations are needed for 64-bit builds.
164// This instantiation will never be used in 32-bit builds, and will cause
165// warnings when sizeof(Size_T) > sizeof(size_t).
166#if SIZE_MAX > UINT32_MAX
168
169// Assertions to ensure this #if stays in sync with SmallVectorSizeType.
170static_assert(sizeof(SmallVectorSizeType<char>) == sizeof(uint64_t),
171 "Expected SmallVectorBase<uint64_t> variant to be in use.");
172#else
173static_assert(sizeof(SmallVectorSizeType<char>) == sizeof(uint32_t),
174 "Expected SmallVectorBase<uint32_t> variant to be in use.");
175#endif
This file defines counterparts of C library allocation functions defined in the namespace 'std'.
return ToRemove size() > 0
static void report_size_overflow(size_t MinSize, size_t MaxSize)
Report that MinSize doesn't fit into this vector's size type.
Definition: SmallVector.cpp:62
static size_t getNewCapacity(size_t MinSize, size_t TSize, size_t OldCapacity)
Definition: SmallVector.cpp:90
static void report_at_maximum_capacity(size_t MaxSize)
Report that this vector is already at maximum capacity.
Definition: SmallVector.cpp:77
This file defines the SmallVector class.
This is all the stuff common to all SmallVectors.
Definition: SmallVector.h:52
void grow_pod(void *FirstEl, size_t MinSize, size_t TSize)
This is an implementation of the grow() method which only works on POD-like data types and is out of ...
void * mallocForGrow(void *FirstEl, size_t MinSize, size_t TSize, size_t &NewCapacity)
This is a helper for grow() that's out of line to reduce code duplication.
void * replaceAllocation(void *NewElts, size_t TSize, size_t NewCapacity, size_t VSize=0)
If vector was first created with capacity 0, getFirstEl() points to the memory right after,...
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small.
Definition: SmallVector.h:1200
Twine - A lightweight data structure for efficiently representing the concatenation of temporary valu...
Definition: Twine.h:81
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
std::conditional_t< sizeof(T)< 4 &&sizeof(void *) >=8, uint64_t, uint32_t > SmallVectorSizeType
Definition: SmallVector.h:110
void report_fatal_error(Error Err, bool gen_crash_diag=true)
Report a serious error, calling any installed error handler.
Definition: Error.cpp:145
LLVM_ATTRIBUTE_RETURNS_NONNULL void * safe_malloc(size_t Sz)
Definition: MemAlloc.h:25
LLVM_ATTRIBUTE_RETURNS_NONNULL void * safe_realloc(void *Ptr, size_t Sz)
Definition: MemAlloc.h:52