reference, declarationdefinition
definition → references, declarations, derived classes, virtual overrides
reference to multiple definitions → definitions
unreferenced
    1
    2
    3
    4
    5
    6
    7
    8
    9
   10
   11
   12
   13
   14
   15
   16
   17
   18
   19
   20
   21
   22
   23
   24
   25
   26
   27
   28
   29
   30
   31
   32
   33
   34
   35
   36
   37
   38
   39
   40
   41
   42
   43
   44
   45
   46
   47
   48
   49
   50
   51
   52
   53
   54
   55
   56
   57
   58
   59
   60
   61
   62
   63
   64
   65
   66
   67
   68
   69
   70
   71
   72
   73
   74
   75
   76
   77
   78
   79
   80
   81
   82
   83
   84
   85
   86
   87
   88
   89
   90
   91
   92
   93
   94
   95
   96
   97
   98
   99
  100
  101
  102
  103
  104
  105
  106
  107
  108
  109
  110
  111
  112
  113
  114
  115
  116
  117
  118
  119
  120
  121
  122
  123
  124
  125
  126
  127
  128
  129
  130
  131
  132
  133
  134
  135
  136
  137
  138
  139
  140
  141
  142
  143
  144
  145
  146
  147
  148
  149
  150
  151
  152
  153
  154
  155
  156
  157
  158
  159
  160
  161
  162
  163
  164
  165
  166
  167
  168
  169
  170
  171
  172
  173
  174
  175
  176
  177
  178
  179
  180
  181
  182
  183
  184
  185
  186
  187
  188
  189
  190
  191
  192
  193
  194
  195
  196
  197
  198
  199
  200
  201
  202
  203
  204
  205
  206
  207
  208
  209
  210
  211
  212
  213
  214
  215
  216
  217
  218
  219
  220
  221
  222
  223
  224
  225
  226
  227
  228
  229
  230
  231
  232
  233
  234
  235
  236
  237
  238
  239
  240
  241
  242
  243
  244
  245
  246
  247
  248
  249
  250
  251
  252
  253
  254
  255
  256
  257
  258
  259
  260
  261
  262
  263
  264
  265
  266
  267
  268
  269
  270
  271
  272
  273
  274
  275
  276
  277
  278
  279
  280
  281
  282
  283
  284
  285
  286
  287
  288
  289
  290
  291
  292
  293
  294
  295
  296
  297
  298
  299
  300
  301
  302
  303
  304
  305
  306
  307
  308
  309
  310
  311
  312
  313
  314
  315
  316
  317
  318
  319
  320
  321
  322
  323
  324
  325
  326
  327
  328
  329
  330
  331
  332
  333
  334
  335
  336
  337
  338
  339
  340
  341
  342
  343
  344
  345
  346
  347
  348
  349
//===-- llvm/Support/Alignment.h - Useful alignment functions ---*- C++ -*-===//
//
// 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 contains types to represent alignments.
// They are instrumented to guarantee some invariants are preserved and prevent
// invalid manipulations.
//
// - Align represents an alignment in bytes, it is always set and always a valid
// power of two, its minimum value is 1 which means no alignment requirements.
//
// - MaybeAlign is an optional type, it may be undefined or set. When it's set
// you can get the underlying Align type by using the getValue() method.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_SUPPORT_ALIGNMENT_H_
#define LLVM_SUPPORT_ALIGNMENT_H_

#include "llvm/ADT/Optional.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/MathExtras.h"
#include <cassert>
#include <limits>

namespace llvm {

#define ALIGN_CHECK_ISPOSITIVE(decl)                                           \
  assert(decl > 0 && (#decl " should be defined"))
#define ALIGN_CHECK_ISSET(decl)                                                \
  assert(decl.hasValue() && (#decl " should be defined"))

/// This struct is a compact representation of a valid (non-zero power of two)
/// alignment.
/// It is suitable for use as static global constants.
struct Align {
private:
  uint8_t ShiftValue = 0; /// The log2 of the required alignment.
                          /// ShiftValue is less than 64 by construction.

  friend struct MaybeAlign;
  friend unsigned Log2(Align);
  friend bool operator==(Align Lhs, Align Rhs);
  friend bool operator!=(Align Lhs, Align Rhs);
  friend bool operator<=(Align Lhs, Align Rhs);
  friend bool operator>=(Align Lhs, Align Rhs);
  friend bool operator<(Align Lhs, Align Rhs);
  friend bool operator>(Align Lhs, Align Rhs);
  friend unsigned encode(struct MaybeAlign A);
  friend struct MaybeAlign decodeMaybeAlign(unsigned Value);

public:
  /// Default is byte-aligned.
  constexpr Align() = default;
  /// Do not perform checks in case of copy/move construct/assign, because the
  /// checks have been performed when building `Other`.
  Align(const Align &Other) = default;
  Align &operator=(const Align &Other) = default;
  Align(Align &&Other) = default;
  Align &operator=(Align &&Other) = default;

  explicit Align(uint64_t Value) {
    assert(Value > 0 && "Value must not be 0");
    assert(llvm::isPowerOf2_64(Value) && "Alignment is not a power of 2");
    ShiftValue = Log2_64(Value);
    assert(ShiftValue < 64 && "Broken invariant");
  }

  /// This is a hole in the type system and should not be abused.
  /// Needed to interact with C for instance.
  uint64_t value() const { return uint64_t(1) << ShiftValue; }

  /// Returns a default constructed Align which corresponds to no alignment.
  /// This is useful to test for unalignment as it conveys clear semantic.
  /// `if (A != Align::None())`
  /// would be better than
  /// `if (A > Align(1))`
  constexpr static const Align None() { return Align(); }
};

/// Treats the value 0 as a 1, so Align is always at least 1.
inline Align assumeAligned(uint64_t Value) {
  return Value ? Align(Value) : Align();
}

/// This struct is a compact representation of a valid (power of two) or
/// undefined (0) alignment.
struct MaybeAlign : public llvm::Optional<Align> {
private:
  using UP = llvm::Optional<Align>;

public:
  /// Default is undefined.
  MaybeAlign() = default;
  /// Do not perform checks in case of copy/move construct/assign, because the
  /// checks have been performed when building `Other`.
  MaybeAlign(const MaybeAlign &Other) = default;
  MaybeAlign &operator=(const MaybeAlign &Other) = default;
  MaybeAlign(MaybeAlign &&Other) = default;
  MaybeAlign &operator=(MaybeAlign &&Other) = default;

  /// Use llvm::Optional<Align> constructor.
  using UP::UP;

  explicit MaybeAlign(uint64_t Value) {
    assert((Value == 0 || llvm::isPowerOf2_64(Value)) &&
           "Alignment is neither 0 nor a power of 2");
    if (Value)
      emplace(Value);
  }

  /// For convenience, returns a valid alignment or 1 if undefined.
  Align valueOrOne() const { return hasValue() ? getValue() : Align(); }
};

/// Checks that SizeInBytes is a multiple of the alignment.
inline bool isAligned(Align Lhs, uint64_t SizeInBytes) {
  return SizeInBytes % Lhs.value() == 0;
}

/// Checks that SizeInBytes is a multiple of the alignment.
/// Returns false if the alignment is undefined.
inline bool isAligned(MaybeAlign Lhs, uint64_t SizeInBytes) {
  ALIGN_CHECK_ISSET(Lhs);
  return SizeInBytes % (*Lhs).value() == 0;
}

/// Returns a multiple of A needed to store `Size` bytes.
inline uint64_t alignTo(uint64_t Size, Align A) {
  return (Size + A.value() - 1) / A.value() * A.value();
}

/// Returns a multiple of A needed to store `Size` bytes.
/// Returns `Size` if current alignment is undefined.
inline uint64_t alignTo(uint64_t Size, MaybeAlign A) {
  return A ? alignTo(Size, A.getValue()) : Size;
}

/// Returns the offset to the next integer (mod 2**64) that is greater than
/// or equal to \p Value and is a multiple of \p Align.
inline uint64_t offsetToAlignment(uint64_t Value, Align Alignment) {
  return alignTo(Value, Alignment) - Value;
}

/// Returns the log2 of the alignment.
inline unsigned Log2(Align A) { return A.ShiftValue; }

/// Returns the log2 of the alignment.
/// \pre A must be defined.
inline unsigned Log2(MaybeAlign A) {
  ALIGN_CHECK_ISSET(A);
  return Log2(A.getValue());
}

/// Returns the alignment that satisfies both alignments.
/// Same semantic as MinAlign.
inline Align commonAlignment(Align A, Align B) { return std::min(A, B); }

/// Returns the alignment that satisfies both alignments.
/// Same semantic as MinAlign.
inline Align commonAlignment(Align A, uint64_t Offset) {
  return Align(MinAlign(A.value(), Offset));
}

/// Returns the alignment that satisfies both alignments.
/// Same semantic as MinAlign.
inline MaybeAlign commonAlignment(MaybeAlign A, MaybeAlign B) {
  return A && B ? commonAlignment(*A, *B) : A ? A : B;
}

/// Returns the alignment that satisfies both alignments.
/// Same semantic as MinAlign.
inline MaybeAlign commonAlignment(MaybeAlign A, uint64_t Offset) {
  return MaybeAlign(MinAlign((*A).value(), Offset));
}

/// Returns a representation of the alignment that encodes undefined as 0.
inline unsigned encode(MaybeAlign A) { return A ? A->ShiftValue + 1 : 0; }

/// Dual operation of the encode function above.
inline MaybeAlign decodeMaybeAlign(unsigned Value) {
  if (Value == 0)
    return MaybeAlign();
  Align Out;
  Out.ShiftValue = Value - 1;
  return Out;
}

/// Returns a representation of the alignment, the encoded value is positive by
/// definition.
inline unsigned encode(Align A) { return encode(MaybeAlign(A)); }

/// Comparisons between Align and scalars. Rhs must be positive.
inline bool operator==(Align Lhs, uint64_t Rhs) {
  ALIGN_CHECK_ISPOSITIVE(Rhs);
  return Lhs.value() == Rhs;
}
inline bool operator!=(Align Lhs, uint64_t Rhs) {
  ALIGN_CHECK_ISPOSITIVE(Rhs);
  return Lhs.value() != Rhs;
}
inline bool operator<=(Align Lhs, uint64_t Rhs) {
  ALIGN_CHECK_ISPOSITIVE(Rhs);
  return Lhs.value() <= Rhs;
}
inline bool operator>=(Align Lhs, uint64_t Rhs) {
  ALIGN_CHECK_ISPOSITIVE(Rhs);
  return Lhs.value() >= Rhs;
}
inline bool operator<(Align Lhs, uint64_t Rhs) {
  ALIGN_CHECK_ISPOSITIVE(Rhs);
  return Lhs.value() < Rhs;
}
inline bool operator>(Align Lhs, uint64_t Rhs) {
  ALIGN_CHECK_ISPOSITIVE(Rhs);
  return Lhs.value() > Rhs;
}

/// Comparisons between MaybeAlign and scalars.
inline bool operator==(MaybeAlign Lhs, uint64_t Rhs) {
  return Lhs ? (*Lhs).value() == Rhs : Rhs == 0;
}
inline bool operator!=(MaybeAlign Lhs, uint64_t Rhs) {
  return Lhs ? (*Lhs).value() != Rhs : Rhs != 0;
}
inline bool operator<=(MaybeAlign Lhs, uint64_t Rhs) {
  ALIGN_CHECK_ISSET(Lhs);
  ALIGN_CHECK_ISPOSITIVE(Rhs);
  return (*Lhs).value() <= Rhs;
}
inline bool operator>=(MaybeAlign Lhs, uint64_t Rhs) {
  ALIGN_CHECK_ISSET(Lhs);
  ALIGN_CHECK_ISPOSITIVE(Rhs);
  return (*Lhs).value() >= Rhs;
}
inline bool operator<(MaybeAlign Lhs, uint64_t Rhs) {
  ALIGN_CHECK_ISSET(Lhs);
  ALIGN_CHECK_ISPOSITIVE(Rhs);
  return (*Lhs).value() < Rhs;
}
inline bool operator>(MaybeAlign Lhs, uint64_t Rhs) {
  ALIGN_CHECK_ISSET(Lhs);
  ALIGN_CHECK_ISPOSITIVE(Rhs);
  return (*Lhs).value() > Rhs;
}

/// Comparisons operators between Align.
inline bool operator==(Align Lhs, Align Rhs) {
  return Lhs.ShiftValue == Rhs.ShiftValue;
}
inline bool operator!=(Align Lhs, Align Rhs) {
  return Lhs.ShiftValue != Rhs.ShiftValue;
}
inline bool operator<=(Align Lhs, Align Rhs) {
  return Lhs.ShiftValue <= Rhs.ShiftValue;
}
inline bool operator>=(Align Lhs, Align Rhs) {
  return Lhs.ShiftValue >= Rhs.ShiftValue;
}
inline bool operator<(Align Lhs, Align Rhs) {
  return Lhs.ShiftValue < Rhs.ShiftValue;
}
inline bool operator>(Align Lhs, Align Rhs) {
  return Lhs.ShiftValue > Rhs.ShiftValue;
}

/// Comparisons operators between Align and MaybeAlign.
inline bool operator==(Align Lhs, MaybeAlign Rhs) {
  ALIGN_CHECK_ISSET(Rhs);
  return Lhs.value() == (*Rhs).value();
}
inline bool operator!=(Align Lhs, MaybeAlign Rhs) {
  ALIGN_CHECK_ISSET(Rhs);
  return Lhs.value() != (*Rhs).value();
}
inline bool operator<=(Align Lhs, MaybeAlign Rhs) {
  ALIGN_CHECK_ISSET(Rhs);
  return Lhs.value() <= (*Rhs).value();
}
inline bool operator>=(Align Lhs, MaybeAlign Rhs) {
  ALIGN_CHECK_ISSET(Rhs);
  return Lhs.value() >= (*Rhs).value();
}
inline bool operator<(Align Lhs, MaybeAlign Rhs) {
  ALIGN_CHECK_ISSET(Rhs);
  return Lhs.value() < (*Rhs).value();
}
inline bool operator>(Align Lhs, MaybeAlign Rhs) {
  ALIGN_CHECK_ISSET(Rhs);
  return Lhs.value() > (*Rhs).value();
}

/// Comparisons operators between MaybeAlign and Align.
inline bool operator==(MaybeAlign Lhs, Align Rhs) {
  ALIGN_CHECK_ISSET(Lhs);
  return Lhs && (*Lhs).value() == Rhs.value();
}
inline bool operator!=(MaybeAlign Lhs, Align Rhs) {
  ALIGN_CHECK_ISSET(Lhs);
  return Lhs && (*Lhs).value() != Rhs.value();
}
inline bool operator<=(MaybeAlign Lhs, Align Rhs) {
  ALIGN_CHECK_ISSET(Lhs);
  return Lhs && (*Lhs).value() <= Rhs.value();
}
inline bool operator>=(MaybeAlign Lhs, Align Rhs) {
  ALIGN_CHECK_ISSET(Lhs);
  return Lhs && (*Lhs).value() >= Rhs.value();
}
inline bool operator<(MaybeAlign Lhs, Align Rhs) {
  ALIGN_CHECK_ISSET(Lhs);
  return Lhs && (*Lhs).value() < Rhs.value();
}
inline bool operator>(MaybeAlign Lhs, Align Rhs) {
  ALIGN_CHECK_ISSET(Lhs);
  return Lhs && (*Lhs).value() > Rhs.value();
}

inline Align operator/(Align Lhs, uint64_t Divisor) {
  assert(llvm::isPowerOf2_64(Divisor) &&
         "Divisor must be positive and a power of 2");
  assert(Lhs != 1 && "Can't halve byte alignment");
  return Align(Lhs.value() / Divisor);
}

inline MaybeAlign operator/(MaybeAlign Lhs, uint64_t Divisor) {
  assert(llvm::isPowerOf2_64(Divisor) &&
         "Divisor must be positive and a power of 2");
  return Lhs ? Lhs.getValue() / Divisor : MaybeAlign();
}

inline Align max(MaybeAlign Lhs, Align Rhs) {
  return Lhs && *Lhs > Rhs ? *Lhs : Rhs;
}

inline Align max(Align Lhs, MaybeAlign Rhs) {
  return Rhs && *Rhs > Lhs ? *Rhs : Lhs;
}

#undef ALIGN_CHECK_ISPOSITIVE
#undef ALIGN_CHECK_ISSET

} // namespace llvm

#endif // LLVM_SUPPORT_ALIGNMENT_H_