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 20 using namespace llvm; 21 22 // Check that no bytes are wasted and everything is well-aligned. 23 namespace { 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 30 struct Struct16B { 31 alignas(16) void *X; 32 }; 33 struct Struct32B { 34 alignas(32) void *X; 35 }; 36 #if defined(_AIX) 37 #pragma GCC diagnostic pop 38 #endif 39 } 40 static_assert(sizeof(SmallVector<void *, 0>) == 41 sizeof(unsigned) * 2 + sizeof(void *), 42 "wasted space in SmallVector size 0"); 43 static_assert(alignof(SmallVector<Struct16B, 0>) >= alignof(Struct16B), 44 "wrong alignment for 16-byte aligned T"); 45 static_assert(alignof(SmallVector<Struct32B, 0>) >= alignof(Struct32B), 46 "wrong alignment for 32-byte aligned T"); 47 static_assert(sizeof(SmallVector<Struct16B, 0>) >= alignof(Struct16B), 48 "missing padding for 16-byte aligned T"); 49 static_assert(sizeof(SmallVector<Struct32B, 0>) >= alignof(Struct32B), 50 "missing padding for 32-byte aligned T"); 51 static_assert(sizeof(SmallVector<void *, 1>) == 52 sizeof(unsigned) * 2 + sizeof(void *) * 2, 53 "wasted space in SmallVector size 1"); 54 55 static_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); 62 static 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 70 report_fatal_error(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); 77 static 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 84 report_fatal_error(Twine(Reason)); 85 #endif 86 } 87 88 // Note: Moving this function into the header may cause performance regression. 89 template <class Size_T> 90 static 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(NewCapacity, MinSize, 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. 121 static void *replaceAllocation(void *NewElts, size_t TSize, size_t NewCapacity, 122 size_t VSize = 0) { 123 void *NewEltsReplace = llvm::safe_malloc(NewCapacity * TSize); 124 if (VSize) 125 memcpy(NewEltsReplace, NewElts, VSize * TSize); 126 free(NewElts); 127 return NewEltsReplace; 128 } 129 130 // Note: Moving this function into the header may cause performance regression. 131 template <class Size_T> 132 void *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(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. 145 template <class Size_T> 146 void 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(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(this->BeginX, NewCapacity * TSize); 160 if (NewElts == FirstEl) 161 NewElts = replaceAllocation(NewElts, TSize, NewCapacity, size()); 162 } 163 164 this->set_allocation_range(NewElts, NewCapacity); 165 } 166 167 template 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 174 template class llvm::SmallVectorBase<uint64_t>; 175 176 // Assertions to ensure this #if stays in sync with SmallVectorSizeType. 177 static_assert(sizeof(SmallVectorSizeType<char>) == sizeof(uint64_t), 178 "Expected SmallVectorBase<uint64_t> variant to be in use."); 179 #else 180 static_assert(sizeof(SmallVectorSizeType<char>) == sizeof(uint32_t), 181 "Expected SmallVectorBase<uint32_t> variant to be in use."); 182 #endif 183