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 41 static_assert(alignof(SmallVector<Struct16B, 0>) >= alignof(Struct16B), 42 "wrong alignment for 16-byte aligned T"); 43 static_assert(alignof(SmallVector<Struct32B, 0>) >= alignof(Struct32B), 44 "wrong alignment for 32-byte aligned T"); 45 static_assert(sizeof(SmallVector<Struct16B, 0>) >= alignof(Struct16B), 46 "missing padding for 16-byte aligned T"); 47 static_assert(sizeof(SmallVector<Struct32B, 0>) >= alignof(Struct32B), 48 "missing padding for 32-byte aligned T"); 49 50 static_assert(sizeof(SmallVector<void *, 0>) == 51 sizeof(unsigned) * 2 + sizeof(void *), 52 "wasted space in SmallVector size 0"); 53 static_assert(sizeof(SmallVector<void *, 1>) == 54 sizeof(unsigned) * 2 + sizeof(void *) * 2, 55 "wasted space in SmallVector size 1"); 56 static_assert(sizeof(SmallVector<char, 0>) == 57 sizeof(void *) * 2 + sizeof(void *), 58 "1 byte elements have word-sized type for size and capacity"); 59 static_assert(sizeof(SmallVector<int16_t, 0>) == 60 sizeof(unsigned) * 2 + sizeof(void *), 61 "2 byte elements have 32-bit type for size and capacity"); 62 63 /// Report that MinSize doesn't fit into this vector's size type. Throws 64 /// std::length_error or calls report_fatal_error. 65 [[noreturn]] static void report_size_overflow(size_t MinSize, size_t MaxSize); 66 static void report_size_overflow(size_t MinSize, size_t MaxSize) { 67 std::string Reason = "SmallVector unable to grow. Requested capacity (" + 68 std::to_string(MinSize) + 69 ") is larger than maximum value for size type (" + 70 std::to_string(MaxSize) + ")"; 71 #ifdef LLVM_ENABLE_EXCEPTIONS 72 throw std::length_error(Reason); 73 #else 74 report_fatal_error(Twine(Reason)); 75 #endif 76 } 77 78 /// Report that this vector is already at maximum capacity. Throws 79 /// std::length_error or calls report_fatal_error. 80 [[noreturn]] static void report_at_maximum_capacity(size_t MaxSize); 81 static void report_at_maximum_capacity(size_t MaxSize) { 82 std::string Reason = 83 "SmallVector capacity unable to grow. Already at maximum size " + 84 std::to_string(MaxSize); 85 #ifdef LLVM_ENABLE_EXCEPTIONS 86 throw std::length_error(Reason); 87 #else 88 report_fatal_error(Twine(Reason)); 89 #endif 90 } 91 92 // Note: Moving this function into the header may cause performance regression. 93 template <class Size_T> 94 static size_t getNewCapacity(size_t MinSize, size_t TSize, size_t OldCapacity) { 95 constexpr size_t MaxSize = std::numeric_limits<Size_T>::max(); 96 97 // Ensure we can fit the new capacity. 98 // This is only going to be applicable when the capacity is 32 bit. 99 if (MinSize > MaxSize) 100 report_size_overflow(MinSize, MaxSize); 101 102 // Ensure we can meet the guarantee of space for at least one more element. 103 // The above check alone will not catch the case where grow is called with a 104 // default MinSize of 0, but the current capacity cannot be increased. 105 // This is only going to be applicable when the capacity is 32 bit. 106 if (OldCapacity == MaxSize) 107 report_at_maximum_capacity(MaxSize); 108 109 // In theory 2*capacity can overflow if the capacity is 64 bit, but the 110 // original capacity would never be large enough for this to be a problem. 111 size_t NewCapacity = 2 * OldCapacity + 1; // Always grow. 112 return std::clamp(NewCapacity, MinSize, MaxSize); 113 } 114 115 template <class Size_T> 116 void *SmallVectorBase<Size_T>::replaceAllocation(void *NewElts, size_t TSize, 117 size_t NewCapacity, 118 size_t VSize) { 119 void *NewEltsReplace = llvm::safe_malloc(NewCapacity * TSize); 120 if (VSize) 121 memcpy(NewEltsReplace, NewElts, VSize * TSize); 122 free(NewElts); 123 return NewEltsReplace; 124 } 125 126 // Note: Moving this function into the header may cause performance regression. 127 template <class Size_T> 128 void *SmallVectorBase<Size_T>::mallocForGrow(void *FirstEl, size_t MinSize, 129 size_t TSize, 130 size_t &NewCapacity) { 131 NewCapacity = getNewCapacity<Size_T>(MinSize, TSize, this->capacity()); 132 // Even if capacity is not 0 now, if the vector was originally created with 133 // capacity 0, it's possible for the malloc to return FirstEl. 134 void *NewElts = llvm::safe_malloc(NewCapacity * TSize); 135 if (NewElts == FirstEl) 136 NewElts = replaceAllocation(NewElts, TSize, NewCapacity); 137 return NewElts; 138 } 139 140 // Note: Moving this function into the header may cause performance regression. 141 template <class Size_T> 142 void SmallVectorBase<Size_T>::grow_pod(void *FirstEl, size_t MinSize, 143 size_t TSize) { 144 size_t NewCapacity = getNewCapacity<Size_T>(MinSize, TSize, this->capacity()); 145 void *NewElts; 146 if (BeginX == FirstEl) { 147 NewElts = llvm::safe_malloc(NewCapacity * TSize); 148 if (NewElts == FirstEl) 149 NewElts = replaceAllocation(NewElts, TSize, NewCapacity); 150 151 // Copy the elements over. No need to run dtors on PODs. 152 memcpy(NewElts, this->BeginX, size() * TSize); 153 } else { 154 // If this wasn't grown from the inline copy, grow the allocated space. 155 NewElts = llvm::safe_realloc(this->BeginX, NewCapacity * TSize); 156 if (NewElts == FirstEl) 157 NewElts = replaceAllocation(NewElts, TSize, NewCapacity, size()); 158 } 159 160 this->set_allocation_range(NewElts, NewCapacity); 161 } 162 163 template class llvm::SmallVectorBase<uint32_t>; 164 165 // Disable the uint64_t instantiation for 32-bit builds. 166 // Both uint32_t and uint64_t instantiations are needed for 64-bit builds. 167 // This instantiation will never be used in 32-bit builds, and will cause 168 // warnings when sizeof(Size_T) > sizeof(size_t). 169 #if SIZE_MAX > UINT32_MAX 170 template class llvm::SmallVectorBase<uint64_t>; 171 172 // Assertions to ensure this #if stays in sync with SmallVectorSizeType. 173 static_assert(sizeof(SmallVectorSizeType<char>) == sizeof(uint64_t), 174 "Expected SmallVectorBase<uint64_t> variant to be in use."); 175 #else 176 static_assert(sizeof(SmallVectorSizeType<char>) == sizeof(uint32_t), 177 "Expected SmallVectorBase<uint32_t> variant to be in use."); 178 #endif 179