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1 //===- ConcatOutputSection.h ------------------------------------*- C++ -*-===//
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2 //
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3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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4 // See https://llvm.org/LICENSE.txt for license information.
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5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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6 //
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7 //===----------------------------------------------------------------------===//
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8
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9 #ifndef LLD_MACHO_MERGED_OUTPUT_SECTION_H
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10 #define LLD_MACHO_MERGED_OUTPUT_SECTION_H
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11
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12 #include "InputSection.h"
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13 #include "OutputSection.h"
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14 #include "lld/Common/LLVM.h"
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15 #include "llvm/ADT/DenseMap.h"
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16 #include "llvm/ADT/MapVector.h"
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17
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18 namespace lld {
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19 namespace macho {
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20
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21 class Defined;
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22
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23 // Linking multiple files will inevitably mean resolving sections in different
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24 // files that are labeled with the same segment and section name. This class
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25 // contains all such sections and writes the data from each section sequentially
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26 // in the final binary.
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27 class ConcatOutputSection : public OutputSection {
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28 public:
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29 explicit ConcatOutputSection(StringRef name)
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30 : OutputSection(ConcatKind, name) {}
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31
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32 const InputSection *firstSection() const { return inputs.front(); }
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33 const InputSection *lastSection() const { return inputs.back(); }
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34
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35 // These accessors will only be valid after finalizing the section
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36 uint64_t getSize() const override { return size; }
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37 uint64_t getFileSize() const override { return fileSize; }
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38
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39 void addInput(InputSection *input);
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40 void finalize() override;
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41 bool needsThunks() const;
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42 uint64_t estimateStubsInRangeVA(size_t callIdx) const;
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43
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44 void writeTo(uint8_t *buf) const override;
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45
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46 std::vector<InputSection *> inputs;
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47 std::vector<InputSection *> thunks;
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48
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49 static bool classof(const OutputSection *sec) {
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50 return sec->kind() == ConcatKind;
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51 }
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52
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53 private:
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54 void mergeFlags(InputSection *input);
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55
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56 size_t size = 0;
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57 uint64_t fileSize = 0;
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58 };
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59
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60 // We maintain one ThunkInfo per real function.
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61 //
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62 // The "active thunk" is represented by the sym/isec pair that
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63 // turns-over during finalize(): as the call-site address advances,
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64 // the active thunk goes out of branch-range, and we create a new
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65 // thunk to take its place.
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66 //
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67 // The remaining members -- bools and counters -- apply to the
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68 // collection of thunks associated with the real function.
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69
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70 struct ThunkInfo {
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71 // These denote the active thunk:
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72 Defined *sym = nullptr; // private-extern symbol for active thunk
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73 InputSection *isec = nullptr; // input section for active thunk
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74
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75 // The following values are cumulative across all thunks on this function
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76 uint32_t callSiteCount = 0; // how many calls to the real function?
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77 uint32_t callSitesUsed = 0; // how many call sites processed so-far?
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78 uint32_t thunkCallCount = 0; // how many call sites went to thunk?
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79 uint8_t sequence = 0; // how many thunks created so-far?
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80 };
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81
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82 extern llvm::DenseMap<Symbol *, ThunkInfo> thunkMap;
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83
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84 } // namespace macho
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85 } // namespace lld
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86
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87 #endif
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