text: //===- llvm/ADT/SmallVector.cpp - 'Normally small' vectors ----------------===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  //
  // This file implements the SmallVector class.
  //
  //===----------------------------------------------------------------------===//
  
  #include "llvm/ADT/SmallVector.h"
  #include "llvm/ADT/Twine.h"
  #include <cstdint>
  #ifdef LLVM_ENABLE_EXCEPTIONS
  #include <stdexcept>
  #endif
  using namespace llvm;
  
  // Check that no bytes are wasted and everything is well-aligned.
  namespace {
  // These structures may cause binary compat warnings on AIX. Suppress the
  // warning since we are only using these types for the static assertions below.
  #if defined(_AIX)
  #pragma GCC diagnostic push
  #pragma GCC diagnostic ignored "-Waix-compat"
  #endif
  struct Struct16B {
    alignas(16) void *X;
  };
  struct Struct32B {
    alignas(32) void *X;
  };
  #if defined(_AIX)
  #pragma GCC diagnostic pop
  #endif
  }
  static_assert(sizeof(SmallVector<void *, 0>) ==
                    sizeof(unsigned) * 2 + sizeof(void *),
                "wasted space in SmallVector size 0");
  static_assert(alignof(SmallVector<Struct16B, 0>) >= alignof(Struct16B),
                "wrong alignment for 16-byte aligned T");
  static_assert(alignof(SmallVector<Struct32B, 0>) >= alignof(Struct32B),
                "wrong alignment for 32-byte aligned T");
  static_assert(sizeof(SmallVector<Struct16B, 0>) >= alignof(Struct16B),
                "missing padding for 16-byte aligned T");
  static_assert(sizeof(SmallVector<Struct32B, 0>) >= alignof(Struct32B),
                "missing padding for 32-byte aligned T");
  static_assert(sizeof(SmallVector<void *, 1>) ==
                    sizeof(unsigned) * 2 + sizeof(void *) * 2,
                "wasted space in SmallVector size 1");
  
  static_assert(sizeof(SmallVector<char, 0>) ==
                    sizeof(void *) * 2 + sizeof(void *),
                "1 byte elements have word-sized type for size and capacity");
  
  /// Report that MinSize doesn't fit into this vector's size type. Throws
  /// std::length_error or calls report_fatal_error.
  [[noreturn]] static void report_size_overflow(size_t MinSize, size_t MaxSize);
  static void report_size_overflow(size_t MinSize, size_t MaxSize) {
    std::string Reason = "SmallVector unable to grow. Requested capacity (" +
                         std::to_string(MinSize) +
                         ") is larger than maximum value for size type (" +
                         std::to_string(MaxSize) + ")";
  #ifdef LLVM_ENABLE_EXCEPTIONS
    throw std::length_error(Reason);
  #else
    report_fatal_error(Twine(Reason));
  #endif
  }
  
  /// Report that this vector is already at maximum capacity. Throws
  /// std::length_error or calls report_fatal_error.
  [[noreturn]] static void report_at_maximum_capacity(size_t MaxSize);
  static void report_at_maximum_capacity(size_t MaxSize) {
    std::string Reason =
        "SmallVector capacity unable to grow. Already at maximum size " +
        std::to_string(MaxSize);
  #ifdef LLVM_ENABLE_EXCEPTIONS
    throw std::length_error(Reason);
  #else
    report_fatal_error(Twine(Reason));
  #endif
  }
  
  // Note: Moving this function into the header may cause performance regression.
  template <class Size_T>
  static size_t getNewCapacity(size_t MinSize, size_t TSize, size_t OldCapacity) {
    constexpr size_t MaxSize = std::numeric_limits<Size_T>::max();
  
    // Ensure we can fit the new capacity.
    // This is only going to be applicable when the capacity is 32 bit.
    if (MinSize > MaxSize)
      report_size_overflow(MinSize, MaxSize);
  
    // Ensure we can meet the guarantee of space for at least one more element.
    // The above check alone will not catch the case where grow is called with a
    // default MinSize of 0, but the current capacity cannot be increased.
    // This is only going to be applicable when the capacity is 32 bit.
    if (OldCapacity == MaxSize)
      report_at_maximum_capacity(MaxSize);
  
    // In theory 2*capacity can overflow if the capacity is 64 bit, but the
    // original capacity would never be large enough for this to be a problem.
    size_t NewCapacity = 2 * OldCapacity + 1; // Always grow.
    return std::min(std::max(NewCapacity, MinSize), MaxSize);
  }
  
  // Note: Moving this function into the header may cause performance regression.
  template <class Size_T>
  void *SmallVectorBase<Size_T>::mallocForGrow(size_t MinSize, size_t TSize,
                                               size_t &NewCapacity) {
    NewCapacity = getNewCapacity<Size_T>(MinSize, TSize, this->capacity());
    return llvm::safe_malloc(NewCapacity * TSize);
  }
  
  // Note: Moving this function into the header may cause performance regression.
  template <class Size_T>
  void SmallVectorBase<Size_T>::grow_pod(void *FirstEl, size_t MinSize,
                                         size_t TSize) {
    size_t NewCapacity = getNewCapacity<Size_T>(MinSize, TSize, this->capacity());
    void *NewElts;
    if (BeginX == FirstEl) {
      NewElts = safe_malloc(NewCapacity * TSize);
  
      // Copy the elements over.  No need to run dtors on PODs.
      memcpy(NewElts, this->BeginX, size() * TSize);
    } else {
      // If this wasn't grown from the inline copy, grow the allocated space.
      NewElts = safe_realloc(this->BeginX, NewCapacity * TSize);
    }
  
    this->BeginX = NewElts;
    this->Capacity = NewCapacity;
  }
  
  template class llvm::SmallVectorBase<uint32_t>;
  
  // Disable the uint64_t instantiation for 32-bit builds.
  // Both uint32_t and uint64_t instantiations are needed for 64-bit builds.
  // This instantiation will never be used in 32-bit builds, and will cause
  // warnings when sizeof(Size_T) > sizeof(size_t).
  #if SIZE_MAX > UINT32_MAX
  template class llvm::SmallVectorBase<uint64_t>;
  
  // Assertions to ensure this #if stays in sync with SmallVectorSizeType.
  static_assert(sizeof(SmallVectorSizeType<char>) == sizeof(uint64_t),
                "Expected SmallVectorBase<uint64_t> variant to be in use.");
  #else
  static_assert(sizeof(SmallVectorSizeType<char>) == sizeof(uint32_t),
                "Expected SmallVectorBase<uint32_t> variant to be in use.");
  #endif
  