1 //===- SectionPriorities.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_SECTION_PRIORITIES_H 10 #define LLD_MACHO_SECTION_PRIORITIES_H 11 12 #include "InputSection.h" 13 #include "llvm/ADT/DenseMap.h" 14 15 namespace lld { 16 namespace macho { 17 18 using SectionPair = std::pair<const InputSection *, const InputSection *>; 19 20 class PriorityBuilder { 21 public: 22 // Reads every input section's call graph profile, and combines them into 23 // callGraphProfile. If an order file is present, any edges where one or both 24 // of the vertices are specified in the order file are discarded. 25 void extractCallGraphProfile(); 26 27 // Reads the order file at `path` into config->priorities. 28 // 29 // An order file has one entry per line, in the following format: 30 // 31 // <cpu>:<object file>:<symbol name> 32 // 33 // <cpu> and <object file> are optional. If not specified, then that entry 34 // matches any symbol of that name. Parsing this format is not quite 35 // straightforward because the symbol name itself can contain colons, so when 36 // encountering a colon, we consider the preceding characters to decide if it 37 // can be a valid CPU type or file path. 38 // 39 // If a symbol is matched by multiple entries, then it takes the 40 // lowest-ordered entry (the one nearest to the front of the list.) 41 // 42 // The file can also have line comments that start with '#'. 43 void parseOrderFile(StringRef path); 44 45 // Returns layout priorities for some or all input sections. Sections are laid 46 // out in decreasing order; that is, a higher priority section will be closer 47 // to the beginning of its output section. 48 // 49 // If either an order file or a call graph profile are present, this is used 50 // as the source of priorities. If both are present, the order file takes 51 // precedence, but the call graph profile is still used for symbols that don't 52 // appear in the order file. If neither is present, an empty map is returned. 53 // 54 // Each section gets assigned the priority of the highest-priority symbol it 55 // contains. 56 llvm::DenseMap<const InputSection *, size_t> buildInputSectionPriorities(); 57 58 private: 59 // The symbol with the highest priority should be ordered first in the output 60 // section (modulo input section contiguity constraints). Using priority 61 // (highest first) instead of order (lowest first) has the convenient property 62 // that the default-constructed zero priority -- for symbols/sections without 63 // a user-defined order -- naturally ends up putting them at the end of the 64 // output. 65 struct SymbolPriorityEntry { 66 // The priority given to a matching symbol, regardless of which object file 67 // it originated from. 68 size_t anyObjectFile = 0; 69 // The priority given to a matching symbol from a particular object file. 70 llvm::DenseMap<llvm::StringRef, size_t> objectFiles; 71 }; 72 73 llvm::Optional<size_t> getSymbolPriority(const Defined *sym); 74 llvm::DenseMap<llvm::StringRef, SymbolPriorityEntry> priorities; 75 llvm::MapVector<SectionPair, uint64_t> callGraphProfile; 76 }; 77 78 extern PriorityBuilder priorityBuilder; 79 } // namespace macho 80 } // namespace lld 81 82 #endif 83