| //===-- 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/MathExtras.h" |
| #include <cassert> |
| #ifndef NDEBUG |
| #include <string> |
| #endif // NDEBUG |
| |
| namespace llvm { |
| |
| #define ALIGN_CHECK_ISPOSITIVE(decl) \ |
| assert(decl > 0 && (#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); |
| |
| /// A trivial type to allow construction of constexpr Align. |
| /// This is currently needed to workaround a bug in GCC 5.3 which prevents |
| /// definition of constexpr assign operators. |
| /// https://stackoverflow.com/questions/46756288/explicitly-defaulted-function-cannot-be-declared-as-constexpr-because-the-implic |
| /// FIXME: Remove this, make all assign operators constexpr and introduce user |
| /// defined literals when we don't have to support GCC 5.3 anymore. |
| /// https://llvm.org/docs/GettingStarted.html#getting-a-modern-host-c-toolchain |
| struct LogValue { |
| uint8_t Log; |
| }; |
| |
| 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`. |
| constexpr Align(const Align &Other) = default; |
| constexpr Align(Align &&Other) = default; |
| Align &operator=(const 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. |
| /// It was decided to deprecate Align::None because it's too close to |
| /// llvm::None which can be used to initialize `MaybeAlign`. |
| /// MaybeAlign = llvm::None means unspecified alignment, |
| /// Align = Align::None() means alignment of one byte. |
| LLVM_ATTRIBUTE_DEPRECATED(constexpr static const Align None(), |
| "Use Align() or Align(1) instead") { |
| return Align(); |
| } |
| |
| /// Allow constructions of constexpr Align. |
| template <size_t kValue> constexpr static LogValue Constant() { |
| return LogValue{static_cast<uint8_t>(CTLog2<kValue>())}; |
| } |
| |
| /// Allow constructions of constexpr Align from types. |
| /// Compile time equivalent to Align(alignof(T)). |
| template <typename T> constexpr static LogValue Of() { |
| return Constant<std::alignment_of<T>::value>(); |
| } |
| |
| /// Constexpr constructor from LogValue type. |
| constexpr Align(LogValue CA) : ShiftValue(CA.Log) {} |
| }; |
| |
| /// 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 Addr is a multiple of the alignment. |
| inline bool isAddrAligned(Align Lhs, const void *Addr) { |
| return isAligned(Lhs, reinterpret_cast<uintptr_t>(Addr)); |
| } |
| |
| /// Returns a multiple of A needed to store `Size` bytes. |
| inline uint64_t alignTo(uint64_t Size, Align A) { |
| const uint64_t Value = A.value(); |
| // The following line is equivalent to `(Size + Value - 1) / Value * Value`. |
| |
| // The division followed by a multiplication can be thought of as a right |
| // shift followed by a left shift which zeros out the extra bits produced in |
| // the bump; `~(Value - 1)` is a mask where all those bits being zeroed out |
| // are just zero. |
| |
| // Most compilers can generate this code but the pattern may be missed when |
| // multiple functions gets inlined. |
| return (Size + Value - 1) & ~(Value - 1U); |
| } |
| |
| /// If non-zero \p Skew is specified, the return value will be a minimal integer |
| /// that is greater than or equal to \p Size and equal to \p A * N + \p Skew for |
| /// some integer N. If \p Skew is larger than \p A, its value is adjusted to '\p |
| /// Skew mod \p A'. |
| /// |
| /// Examples: |
| /// \code |
| /// alignTo(5, Align(8), 7) = 7 |
| /// alignTo(17, Align(8), 1) = 17 |
| /// alignTo(~0LL, Align(8), 3) = 3 |
| /// \endcode |
| inline uint64_t alignTo(uint64_t Size, Align A, uint64_t Skew) { |
| const uint64_t Value = A.value(); |
| Skew %= Value; |
| return ((Size + Value - 1 - Skew) & ~(Value - 1U)) + Skew; |
| } |
| |
| /// 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; |
| } |
| |
| /// Aligns `Addr` to `Alignment` bytes, rounding up. |
| inline uintptr_t alignAddr(const void *Addr, Align Alignment) { |
| uintptr_t ArithAddr = reinterpret_cast<uintptr_t>(Addr); |
| assert(static_cast<uintptr_t>(ArithAddr + Alignment.value() - 1) >= |
| ArithAddr && |
| "Overflow"); |
| return alignTo(ArithAddr, Alignment); |
| } |
| |
| /// 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 necessary adjustment for aligning `Addr` to `Alignment` |
| /// bytes, rounding up. |
| inline uint64_t offsetToAlignedAddr(const void *Addr, Align Alignment) { |
| return offsetToAlignment(reinterpret_cast<uintptr_t>(Addr), Alignment); |
| } |
| |
| /// Returns the log2 of the alignment. |
| inline unsigned Log2(Align A) { return A.ShiftValue; } |
| |
| /// 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; |
| } |
| |
| /// 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; |
| } |
| |
| // Don't allow relational comparisons with MaybeAlign. |
| bool operator<=(Align Lhs, MaybeAlign Rhs) = delete; |
| bool operator>=(Align Lhs, MaybeAlign Rhs) = delete; |
| bool operator<(Align Lhs, MaybeAlign Rhs) = delete; |
| bool operator>(Align Lhs, MaybeAlign Rhs) = delete; |
| |
| bool operator<=(MaybeAlign Lhs, Align Rhs) = delete; |
| bool operator>=(MaybeAlign Lhs, Align Rhs) = delete; |
| bool operator<(MaybeAlign Lhs, Align Rhs) = delete; |
| bool operator>(MaybeAlign Lhs, Align Rhs) = delete; |
| |
| bool operator<=(MaybeAlign Lhs, MaybeAlign Rhs) = delete; |
| bool operator>=(MaybeAlign Lhs, MaybeAlign Rhs) = delete; |
| bool operator<(MaybeAlign Lhs, MaybeAlign Rhs) = delete; |
| bool operator>(MaybeAlign Lhs, MaybeAlign Rhs) = delete; |
| |
| inline Align operator*(Align Lhs, uint64_t Rhs) { |
| assert(Rhs > 0 && "Rhs must be positive"); |
| return Align(Lhs.value() * Rhs); |
| } |
| |
| inline MaybeAlign operator*(MaybeAlign Lhs, uint64_t Rhs) { |
| assert(Rhs > 0 && "Rhs must be positive"); |
| return Lhs ? Lhs.getValue() * Rhs : MaybeAlign(); |
| } |
| |
| 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; |
| } |
| |
| #ifndef NDEBUG |
| // For usage in LLVM_DEBUG macros. |
| inline std::string DebugStr(const Align &A) { |
| return std::to_string(A.value()); |
| } |
| // For usage in LLVM_DEBUG macros. |
| inline std::string DebugStr(const MaybeAlign &MA) { |
| if (MA) |
| return std::to_string(MA->value()); |
| return "None"; |
| } |
| #endif // NDEBUG |
| |
| #undef ALIGN_CHECK_ISPOSITIVE |
| |
| } // namespace llvm |
| |
| #endif // LLVM_SUPPORT_ALIGNMENT_H_ |