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 <cstdint>
  15 #ifdef LLVM_ENABLE_EXCEPTIONS
  16 #include <stdexcept>
  17 #endif
  18 using namespace llvm;
  19
  20 // Check that no bytes are wasted and everything is well-aligned.
  21 namespace {
  22 struct Struct16B {
  23   alignas(16) void *X;
  24 };
  25 struct Struct32B {
  26   alignas(32) void *X;
  27 };
  28 }
  29 static_assert(sizeof(SmallVector<void *, 0>) ==
  30                   sizeof(unsigned) * 2 + sizeof(void *),
  31               "wasted space in SmallVector size 0");
  32 static_assert(alignof(SmallVector<Struct16B, 0>) >= alignof(Struct16B),
  33               "wrong alignment for 16-byte aligned T");
  34 static_assert(alignof(SmallVector<Struct32B, 0>) >= alignof(Struct32B),
  35               "wrong alignment for 32-byte aligned T");
  36 static_assert(sizeof(SmallVector<Struct16B, 0>) >= alignof(Struct16B),
  37               "missing padding for 16-byte aligned T");
  38 static_assert(sizeof(SmallVector<Struct32B, 0>) >= alignof(Struct32B),
  39               "missing padding for 32-byte aligned T");
  40 static_assert(sizeof(SmallVector<void *, 1>) ==
  41                   sizeof(unsigned) * 2 + sizeof(void *) * 2,
  42               "wasted space in SmallVector size 1");
  43
  44 static_assert(sizeof(SmallVector<char, 0>) ==
  45                   sizeof(void *) * 2 + sizeof(void *),
  46               "1 byte elements have word-sized type for size and capacity");
  47
  48 /// Report that MinSize doesn't fit into this vector's size type. Throws
  49 /// std::length_error or calls report_fatal_error.
  50 [[noreturn]] static void report_size_overflow(size_t MinSize, size_t MaxSize);
  51 static void report_size_overflow(size_t MinSize, size_t MaxSize) {
  52   std::string Reason = "SmallVector unable to grow. Requested capacity (" +
  53                        std::to_string(MinSize) +
  54                        ") is larger than maximum value for size type (" +
  55                        std::to_string(MaxSize) + ")";
  56 #ifdef LLVM_ENABLE_EXCEPTIONS
  57   throw std::length_error(Reason);
  58 #else
  59   report_fatal_error(Reason);
  60 #endif
  61 }
  62
  63 /// Report that this vector is already at maximum capacity. Throws
  64 /// std::length_error or calls report_fatal_error.
  65 [[noreturn]] static void report_at_maximum_capacity(size_t MaxSize);
  66 static void report_at_maximum_capacity(size_t MaxSize) {
  67   std::string Reason =
  68       "SmallVector capacity unable to grow. Already at maximum size " +
  69       std::to_string(MaxSize);
  70 #ifdef LLVM_ENABLE_EXCEPTIONS
  71   throw std::length_error(Reason);
  72 #else
  73   report_fatal_error(Reason);
  74 #endif
  75 }
  76
  77 // Note: Moving this function into the header may cause performance regression.
  78 template <class Size_T>
  79 static size_t getNewCapacity(size_t MinSize, size_t TSize, size_t OldCapacity) {
  80   constexpr size_t MaxSize = std::numeric_limits<Size_T>::max();
  81
  82   // Ensure we can fit the new capacity.
  83   // This is only going to be applicable when the capacity is 32 bit.
  84   if (MinSize > MaxSize)
  85     report_size_overflow(MinSize, MaxSize);
  86
  87   // Ensure we can meet the guarantee of space for at least one more element.
  88   // The above check alone will not catch the case where grow is called with a
  89   // default MinSize of 0, but the current capacity cannot be increased.
  90   // This is only going to be applicable when the capacity is 32 bit.
  91   if (OldCapacity == MaxSize)
  92     report_at_maximum_capacity(MaxSize);
  93
  94   // In theory 2*capacity can overflow if the capacity is 64 bit, but the
  95   // original capacity would never be large enough for this to be a problem.
  96   size_t NewCapacity = 2 * OldCapacity + 1; // Always grow.
  97   return std::min(std::max(NewCapacity, MinSize), MaxSize);
  98 }
  99
 100 // Note: Moving this function into the header may cause performance regression.
 101 template <class Size_T>
 102 void *SmallVectorBase<Size_T>::mallocForGrow(size_t MinSize, size_t TSize,
 103                                              size_t &NewCapacity) {
 104   NewCapacity = getNewCapacity<Size_T>(MinSize, TSize, this->capacity());
 105   return llvm::safe_malloc(NewCapacity * TSize);
 106 }
 107
 108 // Note: Moving this function into the header may cause performance regression.
 109 template <class Size_T>
 110 void SmallVectorBase<Size_T>::grow_pod(void *FirstEl, size_t MinSize,
 111                                        size_t TSize) {
 112   size_t NewCapacity = getNewCapacity<Size_T>(MinSize, TSize, this->capacity());
 113   void *NewElts;
 114   if (BeginX == FirstEl) {
 115     NewElts = safe_malloc(NewCapacity * TSize);
 116
 117     // Copy the elements over.  No need to run dtors on PODs.
 118     memcpy(NewElts, this->BeginX, size() * TSize);
 119   } else {
 120     // If this wasn't grown from the inline copy, grow the allocated space.
 121     NewElts = safe_realloc(this->BeginX, NewCapacity * TSize);
 122   }
 123
 124   this->BeginX = NewElts;
 125   this->Capacity = NewCapacity;
 126 }
 127
 128 template class llvm::SmallVectorBase<uint32_t>;
 129
 130 // Disable the uint64_t instantiation for 32-bit builds.
 131 // Both uint32_t and uint64_t instantiations are needed for 64-bit builds.
 132 // This instantiation will never be used in 32-bit builds, and will cause
 133 // warnings when sizeof(Size_T) > sizeof(size_t).
 134 #if SIZE_MAX > UINT32_MAX
 135 template class llvm::SmallVectorBase<uint64_t>;
 136
 137 // Assertions to ensure this #if stays in sync with SmallVectorSizeType.
 138 static_assert(sizeof(SmallVectorSizeType<char>) == sizeof(uint64_t),
 139               "Expected SmallVectorBase<uint64_t> variant to be in use.");
 140 #else
 141 static_assert(sizeof(SmallVectorSizeType<char>) == sizeof(uint32_t),
 142               "Expected SmallVectorBase<uint32_t> variant to be in use.");
 143 #endif