1 //===- ConcatOutputSection.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 LLD_MACHO_MERGED_OUTPUT_SECTION_H 10 #define LLD_MACHO_MERGED_OUTPUT_SECTION_H 11 12 #include "InputSection.h" 13 #include "OutputSection.h" 14 #include "lld/Common/LLVM.h" 15 #include "llvm/ADT/DenseMap.h" 16 #include "llvm/ADT/MapVector.h" 17 18 namespace lld { 19 namespace macho { 20 21 class Defined; 22 23 // Linking multiple files will inevitably mean resolving sections in different 24 // files that are labeled with the same segment and section name. This class 25 // contains all such sections and writes the data from each section sequentially 26 // in the final binary. 27 class ConcatOutputSection final : public OutputSection { 28 public: 29 explicit ConcatOutputSection(StringRef name) 30 : OutputSection(ConcatKind, name) {} 31 32 const ConcatInputSection *firstSection() const { return inputs.front(); } 33 const ConcatInputSection *lastSection() const { return inputs.back(); } 34 bool isNeeded() const override { return !inputs.empty(); } 35 36 // These accessors will only be valid after finalizing the section 37 uint64_t getSize() const override { return size; } 38 uint64_t getFileSize() const override { return fileSize; } 39 40 void addInput(ConcatInputSection *input); 41 void finalize() override; 42 bool needsThunks() const; 43 uint64_t estimateStubsInRangeVA(size_t callIdx) const; 44 45 void writeTo(uint8_t *buf) const override; 46 47 std::vector<ConcatInputSection *> inputs; 48 std::vector<ConcatInputSection *> thunks; 49 50 static bool classof(const OutputSection *sec) { 51 return sec->kind() == ConcatKind; 52 } 53 54 static ConcatOutputSection *getOrCreateForInput(const InputSection *); 55 56 private: 57 void finalizeFlags(InputSection *input); 58 59 size_t size = 0; 60 uint64_t fileSize = 0; 61 }; 62 63 // We maintain one ThunkInfo per real function. 64 // 65 // The "active thunk" is represented by the sym/isec pair that 66 // turns-over during finalize(): as the call-site address advances, 67 // the active thunk goes out of branch-range, and we create a new 68 // thunk to take its place. 69 // 70 // The remaining members -- bools and counters -- apply to the 71 // collection of thunks associated with the real function. 72 73 struct ThunkInfo { 74 // These denote the active thunk: 75 Defined *sym = nullptr; // private-extern symbol for active thunk 76 ConcatInputSection *isec = nullptr; // input section for active thunk 77 78 // The following values are cumulative across all thunks on this function 79 uint32_t callSiteCount = 0; // how many calls to the real function? 80 uint32_t callSitesUsed = 0; // how many call sites processed so-far? 81 uint32_t thunkCallCount = 0; // how many call sites went to thunk? 82 uint8_t sequence = 0; // how many thunks created so-far? 83 }; 84 85 NamePair maybeRenameSection(NamePair key); 86 87 // Output sections are added to output segments in iteration order 88 // of ConcatOutputSection, so must have deterministic iteration order. 89 extern llvm::MapVector<NamePair, ConcatOutputSection *> concatOutputSections; 90 91 extern llvm::DenseMap<Symbol *, ThunkInfo> thunkMap; 92 93 } // namespace macho 94 } // namespace lld 95 96 #endif 97