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