1 //===- NonRelocatableStringpool.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-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #ifndef LLVM_CODEGEN_NONRELOCATABLESTRINGPOOL_H 10 #define LLVM_CODEGEN_NONRELOCATABLESTRINGPOOL_H 11 12 #include "llvm/CodeGen/DwarfStringPoolEntry.h" 13 #include "llvm/Support/Allocator.h" 14 #include <cstdint> 15 #include <vector> 16 17 namespace llvm { 18 19 /// A string table that doesn't need relocations. 20 /// 21 /// Use this class when a string table doesn't need relocations. 22 /// This class provides this ability by just associating offsets with strings. 23 class NonRelocatableStringpool { 24 public: 25 /// Entries are stored into the StringMap and simply linked together through 26 /// the second element of this pair in order to keep track of insertion 27 /// order. 28 using MapTy = StringMap<DwarfStringPoolEntry, BumpPtrAllocator>; 29 30 NonRelocatableStringpool(bool PutEmptyString = false) { 31 if (PutEmptyString) 32 getEntry(""); 33 } 34 35 DwarfStringPoolEntryRef getEntry(StringRef S); 36 37 /// Get the offset of string \p S in the string table. This can insert a new 38 /// element or return the offset of a pre-existing one. getStringOffset(StringRef S)39 uint64_t getStringOffset(StringRef S) { return getEntry(S).getOffset(); } 40 41 /// Get permanent storage for \p S (but do not necessarily emit \p S in the 42 /// output section). A latter call to getStringOffset() with the same string 43 /// will chain it though. 44 /// 45 /// \returns The StringRef that points to permanent storage to use 46 /// in place of \p S. 47 StringRef internString(StringRef S); 48 getSize()49 uint64_t getSize() { return CurrentEndOffset; } 50 51 /// Return the list of strings to be emitted. This does not contain the 52 /// strings which were added via internString only. 53 std::vector<DwarfStringPoolEntryRef> getEntriesForEmission() const; 54 55 private: 56 MapTy Strings; 57 uint64_t CurrentEndOffset = 0; 58 unsigned NumEntries = 0; 59 }; 60 61 /// Helper for making strong types. 62 template <typename T, typename S> class StrongType : public T { 63 public: 64 template <typename... Args> StrongType(Args...A)65 explicit StrongType(Args... A) : T(std::forward<Args>(A)...) {} 66 }; 67 68 /// It's very easy to introduce bugs by passing the wrong string pool. 69 /// By using strong types the interface enforces that the right 70 /// kind of pool is used. 71 struct UniqueTag {}; 72 struct OffsetsTag {}; 73 using UniquingStringPool = StrongType<NonRelocatableStringpool, UniqueTag>; 74 using OffsetsStringPool = StrongType<NonRelocatableStringpool, OffsetsTag>; 75 76 } // end namespace llvm 77 78 #endif // LLVM_CODEGEN_NONRELOCATABLESTRINGPOOL_H 79