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//===- 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
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