llvm/lib/Support/SmallVector.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-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