183 lines · cpp
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-exception6//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_EXCEPTIONS18#include <stdexcept>19#endif20using 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 the25// warning since we are only using these types for the static assertions below.26#if defined(_AIX)27#pragma GCC diagnostic push28#pragma GCC diagnostic ignored "-Waix-compat"29#endif30struct Struct16B {31 alignas(16) void *X;32};33struct Struct32B {34 alignas(32) void *X;35};36#if defined(_AIX)37#pragma GCC diagnostic pop38#endif39}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. Throws60/// 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_EXCEPTIONS68 throw std::length_error(Reason);69#else70 report_fatal_error(Twine(Reason));71#endif72}73 74/// Report that this vector is already at maximum capacity. Throws75/// 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_EXCEPTIONS82 throw std::length_error(Reason);83#else84 report_fatal_error(Twine(Reason));85#endif86}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 a100 // 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 the106 // 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 the112/// 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 no115/// allocation was done (true) and the memory will not be freed in the116/// destructor. If a VSize is given (vector size), also copy that many117/// elements to the new allocation - used if realloca fails to increase118/// space, and happens to allocate precisely at BeginX.119/// This is unlikely to be called often, but resolves a memory leak when the120/// 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(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.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 with137 // 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.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(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 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 cause172// warnings when sizeof(Size_T) > sizeof(size_t).173#if SIZE_MAX > UINT32_MAX174template 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#else180static_assert(sizeof(SmallVectorSizeType<char>) == sizeof(uint32_t),181 "Expected SmallVectorBase<uint32_t> variant to be in use.");182#endif183