allwpilib/wpiutil/src/main/native/cpp/llvm/SmallVector.cpp

//===- 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 "wpi/SmallVector.h"
#include <cstdint>
#ifdef LLVM_ENABLE_EXCEPTIONS
#include <stdexcept>
#endif
using namespace wpi;

// Check that no bytes are wasted and everything is well-aligned.
namespace {
struct Struct16B {
  alignas(16) void *X;
};
struct Struct32B {
  alignas(32) void *X;
};
}
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");

/// Report that MinSize doesn't fit into this vector's size type. Throws
/// std::length_error or calls report_fatal_error.
LLVM_ATTRIBUTE_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(Reason);
#endif
}

/// Report that this vector is already at maximum capacity. Throws
/// std::length_error or calls report_fatal_error.
LLVM_ATTRIBUTE_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(Reason);
#endif
}

// Note: Moving this function into the header may cause performance regression.
static size_t getNewCapacity(size_t MinSize, size_t TSize, size_t OldCapacity) {
  constexpr size_t MaxSize = std::numeric_limits<unsigned>::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.
void *SmallVectorBase::mallocForGrow(size_t MinSize, size_t TSize,
                                             size_t &NewCapacity) {
  NewCapacity = getNewCapacity(MinSize, TSize, this->capacity());
  return wpi::safe_malloc(NewCapacity * TSize);
}

// Note: Moving this function into the header may cause performance regression.
void SmallVectorBase::grow_pod(void *FirstEl, size_t MinSize,
                                       size_t TSize) {
  size_t NewCapacity = getNewCapacity(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;
}