134 lines · c
1//===--------------------- BitcastBuffer.h ----------------------*- C++ -*-===//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-exception6//7//===----------------------------------------------------------------------===//8#ifndef LLVM_CLANG_AST_INTERP_BITCAST_BUFFER_H9#define LLVM_CLANG_AST_INTERP_BITCAST_BUFFER_H10 11#include "llvm/ADT/SmallVector.h"12#include <cassert>13#include <cstddef>14#include <memory>15 16namespace clang {17namespace interp {18 19enum class Endian { Little, Big };20 21struct Bytes;22 23/// A quantity in bits.24struct Bits {25 size_t N = 0;26 Bits() = default;27 static Bits zero() { return Bits(0); }28 explicit Bits(size_t Quantity) : N(Quantity) {}29 size_t getQuantity() const { return N; }30 size_t roundToBytes() const { return N / 8; }31 size_t getOffsetInByte() const { return N % 8; }32 bool isFullByte() const { return N % 8 == 0; }33 bool nonZero() const { return N != 0; }34 bool isZero() const { return N == 0; }35 Bytes toBytes() const;36 37 Bits operator-(Bits Other) const { return Bits(N - Other.N); }38 Bits operator+(Bits Other) const { return Bits(N + Other.N); }39 Bits operator+=(size_t O) {40 N += O;41 return *this;42 }43 Bits operator+=(Bits O) {44 N += O.N;45 return *this;46 }47 48 bool operator>=(Bits Other) const { return N >= Other.N; }49 bool operator<=(Bits Other) const { return N <= Other.N; }50 bool operator==(Bits Other) const { return N == Other.N; }51 bool operator!=(Bits Other) const { return N != Other.N; }52};53 54/// A quantity in bytes.55struct Bytes {56 size_t N;57 explicit Bytes(size_t Quantity) : N(Quantity) {}58 size_t getQuantity() const { return N; }59 Bits toBits() const { return Bits(N * 8); }60};61 62inline Bytes Bits::toBytes() const {63 assert(isFullByte());64 return Bytes(N / 8);65}66 67/// A bit range. Both Start and End are inclusive.68struct BitRange {69 Bits Start;70 Bits End;71 72 BitRange(Bits Start, Bits End) : Start(Start), End(End) {}73 Bits size() const { return End - Start + Bits(1); }74 bool operator<(BitRange Other) const { return Start.N < Other.Start.N; }75 76 bool contains(Bits B) { return Start <= B && End >= B; }77};78 79/// Track what bits have been initialized to known values and which ones80/// have indeterminate value.81struct BitcastBuffer {82 Bits FinalBitSize;83 std::unique_ptr<std::byte[]> Data;84 llvm::SmallVector<BitRange> InitializedBits;85 86 BitcastBuffer(Bits FinalBitSize) : FinalBitSize(FinalBitSize) {87 assert(FinalBitSize.isFullByte());88 unsigned ByteSize = FinalBitSize.roundToBytes();89 Data = std::make_unique<std::byte[]>(ByteSize);90 }91 92 /// Returns the byte at the given offset.93 std::byte *atByte(unsigned Offset) {94 assert(Offset < FinalBitSize.roundToBytes());95 return Data.get() + Offset;96 }97 98 /// Returns the buffer size in bits.99 Bits size() const { return FinalBitSize; }100 Bytes byteSize() const { return FinalBitSize.toBytes(); }101 102 /// Returns \c true if all bits in the buffer have been initialized.103 bool allInitialized() const;104 /// Marks the bits in the given range as initialized.105 /// FIXME: Can we do this automatically in pushData()?106 void markInitialized(Bits Start, Bits Length);107 bool rangeInitialized(Bits Offset, Bits Length) const;108 109 /// Push \p BitWidth bits at \p BitOffset from \p In into the buffer.110 /// \p TargetEndianness is the endianness of the target we're compiling for.111 /// \p In must hold at least \p BitWidth many bits.112 void pushData(const std::byte *In, Bits BitOffset, Bits BitWidth,113 Endian TargetEndianness);114 115 /// Copy \p BitWidth bits at offset \p BitOffset from the buffer.116 /// \p TargetEndianness is the endianness of the target we're compiling for.117 ///118 /// The returned output holds exactly (\p FullBitWidth / 8) bytes.119 std::unique_ptr<std::byte[]> copyBits(Bits BitOffset, Bits BitWidth,120 Bits FullBitWidth,121 Endian TargetEndianness) const;122 123 /// Dereferences the value at the given offset.124 template <typename T> T deref(Bytes Offset) const {125 assert(Offset.getQuantity() < FinalBitSize.roundToBytes());126 assert((Offset.getQuantity() + sizeof(T)) <= FinalBitSize.roundToBytes());127 return *reinterpret_cast<T *>(Data.get() + Offset.getQuantity());128 }129};130 131} // namespace interp132} // namespace clang133#endif134