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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-exception6//7//===----------------------------------------------------------------------===//8 9#ifndef LLD_MACHO_CONCAT_OUTPUT_SECTION_H10#define LLD_MACHO_CONCAT_OUTPUT_SECTION_H11 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 18namespace lld::macho {19 20class Defined;21 22// Linking multiple files will inevitably mean resolving sections in different23// files that are labeled with the same segment and section name. This class24// contains all such sections and writes the data from each section sequentially25// in the final binary.26class ConcatOutputSection : public OutputSection {27public:28 explicit ConcatOutputSection(StringRef name,29 OutputSection::Kind kind = ConcatKind)30 : OutputSection(kind, 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 section37 uint64_t getSize() const override { return size; }38 uint64_t getFileSize() const override { return fileSize; }39 40 // Assign values to InputSection::outSecOff. In contrast to TextOutputSection,41 // which does this in its implementation of `finalize()`, we can do this42 // without `finalize()`'s sequential guarantees detailed in the block comment43 // of `OutputSection::finalize()`.44 virtual void finalizeContents();45 46 void addInput(ConcatInputSection *input);47 void writeTo(uint8_t *buf) const override;48 49 static bool classof(const OutputSection *sec) {50 return sec->kind() == ConcatKind || sec->kind() == TextKind;51 }52 53 static ConcatOutputSection *getOrCreateForInput(const InputSection *);54 55 std::vector<ConcatInputSection *> inputs;56 57protected:58 size_t size = 0;59 uint64_t fileSize = 0;60 void finalizeOne(ConcatInputSection *);61 62private:63 void finalizeFlags(InputSection *input);64};65 66// ConcatOutputSections that contain code (text) require special handling to67// support thunk insertion.68class TextOutputSection : public ConcatOutputSection {69public:70 explicit TextOutputSection(StringRef name)71 : ConcatOutputSection(name, TextKind) {}72 void finalizeContents() override {}73 void finalize() override;74 bool needsThunks() const;75 ArrayRef<ConcatInputSection *> getThunks() const { return thunks; }76 void writeTo(uint8_t *buf) const override;77 78 static bool classof(const OutputSection *sec) {79 return sec->kind() == TextKind;80 }81 82private:83 uint64_t estimateBranchTargetThresholdVA(size_t callIdx) const;84 85 std::vector<ConcatInputSection *> thunks;86};87 88// We maintain one ThunkInfo per real function.89//90// The "active thunk" is represented by the sym/isec pair that91// turns-over during finalize(): as the call-site address advances,92// the active thunk goes out of branch-range, and we create a new93// thunk to take its place.94//95// The remaining members -- bools and counters -- apply to the96// collection of thunks associated with the real function.97 98struct ThunkInfo {99 // These denote the active thunk:100 Defined *sym = nullptr; // private-extern symbol for active thunk101 ConcatInputSection *isec = nullptr; // input section for active thunk102 103 // The following values are cumulative across all thunks on this function104 uint32_t callSiteCount = 0; // how many calls to the real function?105 uint32_t callSitesUsed = 0; // how many call sites processed so-far?106 uint32_t thunkCallCount = 0; // how many call sites went to thunk?107 uint8_t sequence = 0; // how many thunks created so-far?108};109 110NamePair maybeRenameSection(NamePair key);111 112// Output sections are added to output segments in iteration order113// of ConcatOutputSection, so must have deterministic iteration order.114extern llvm::MapVector<NamePair, ConcatOutputSection *> concatOutputSections;115 116extern llvm::DenseMap<Symbol *, ThunkInfo> thunkMap;117 118} // namespace lld::macho119 120#endif121