| //===- SectionPriorities.h --------------------------------------*- C++ -*-===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLD_MACHO_SECTION_PRIORITIES_H |
| #define LLD_MACHO_SECTION_PRIORITIES_H |
| |
| #include "InputSection.h" |
| #include "llvm/ADT/DenseMap.h" |
| |
| namespace lld::macho { |
| |
| using SectionPair = std::pair<const InputSection *, const InputSection *>; |
| |
| class PriorityBuilder { |
| public: |
| // Reads every input section's call graph profile, and combines them into |
| // callGraphProfile. If an order file is present, any edges where one or both |
| // of the vertices are specified in the order file are discarded. |
| void extractCallGraphProfile(); |
| |
| // Reads the order file at `path` into config->priorities. |
| // |
| // An order file has one entry per line, in the following format: |
| // |
| // <cpu>:<object file>:<symbol name> |
| // |
| // <cpu> and <object file> are optional. If not specified, then that entry |
| // matches any symbol of that name. Parsing this format is not quite |
| // straightforward because the symbol name itself can contain colons, so when |
| // encountering a colon, we consider the preceding characters to decide if it |
| // can be a valid CPU type or file path. |
| // |
| // If a symbol is matched by multiple entries, then it takes the |
| // lowest-ordered entry (the one nearest to the front of the list.) |
| // |
| // The file can also have line comments that start with '#'. |
| void parseOrderFile(StringRef path); |
| |
| // Returns layout priorities for some or all input sections. Sections are laid |
| // out in decreasing order; that is, a higher priority section will be closer |
| // to the beginning of its output section. |
| // |
| // If either an order file or a call graph profile are present, this is used |
| // as the source of priorities. If both are present, the order file takes |
| // precedence, but the call graph profile is still used for symbols that don't |
| // appear in the order file. If neither is present, an empty map is returned. |
| // |
| // Each section gets assigned the priority of the highest-priority symbol it |
| // contains. |
| llvm::DenseMap<const InputSection *, size_t> buildInputSectionPriorities(); |
| |
| private: |
| // The symbol with the highest priority should be ordered first in the output |
| // section (modulo input section contiguity constraints). Using priority |
| // (highest first) instead of order (lowest first) has the convenient property |
| // that the default-constructed zero priority -- for symbols/sections without |
| // a user-defined order -- naturally ends up putting them at the end of the |
| // output. |
| struct SymbolPriorityEntry { |
| // The priority given to a matching symbol, regardless of which object file |
| // it originated from. |
| size_t anyObjectFile = 0; |
| // The priority given to a matching symbol from a particular object file. |
| llvm::DenseMap<llvm::StringRef, size_t> objectFiles; |
| }; |
| |
| std::optional<size_t> getSymbolPriority(const Defined *sym); |
| llvm::DenseMap<llvm::StringRef, SymbolPriorityEntry> priorities; |
| llvm::MapVector<SectionPair, uint64_t> callGraphProfile; |
| }; |
| |
| extern PriorityBuilder priorityBuilder; |
| } // namespace lld::macho |
| |
| #endif |