llvm-capstone/lld/MachO/OutputSegment.h
Jez Ng 3646ee503d [lld-macho] Refactor segment/section creation, sorting, and merging
Summary:
There were a few issues with the previous setup:

1. The section sorting comparator used a declarative map of section names to
  determine the correct order, but it turns out we need to match on more than
  just names -- in particular, an upcoming diff will sort based on whether the
  S_ZERO_FILL flag is set. This diff changes the sorter to a more imperative but
  flexible form.

2. We were sorting OutputSections stored in a MapVector, which left the
  MapVector in an inconsistent state -- the wrong keys map to the wrong values!
  In practice, we weren't doing key lookups (only container iteration) after the
  sort, so this was fine, but it was still a dubious state of affairs. This diff
  copies the OutputSections to a vector before sorting them.

3. We were adding unneeded OutputSections to OutputSegments and then filtering
  them out later, which meant that we had to remember whether an OutputSegment
  was in a pre- or post-filtered state. This diff only adds the sections to the
  segments if they are needed.

In addition to those major changes, two minor ones worth noting:

1. I renamed all OutputSection variable names to `osec`, to parallel `isec`.
  Previously we were using some inconsistent combination of `osec`, `os`, and
  `section`.

2. I added a check (and a test) for InputSections with names that clashed with
  those of our synthetic OutputSections.

Reviewers: #lld-macho

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D81887
2020-06-21 17:13:59 -07:00

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1.6 KiB
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//===- OutputSegment.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_OUTPUT_SEGMENT_H
#define LLD_MACHO_OUTPUT_SEGMENT_H
#include "OutputSection.h"
#include "lld/Common/LLVM.h"
namespace lld {
namespace macho {
namespace segment_names {
constexpr const char pageZero[] = "__PAGEZERO";
constexpr const char text[] = "__TEXT";
constexpr const char data[] = "__DATA";
constexpr const char linkEdit[] = "__LINKEDIT";
constexpr const char dataConst[] = "__DATA_CONST";
} // namespace segment_names
class OutputSection;
class InputSection;
class OutputSegment {
public:
const OutputSection *firstSection() const { return sections.front(); }
const OutputSection *lastSection() const { return sections.back(); }
void addOutputSection(OutputSection *os);
void sortOutputSections(
llvm::function_ref<bool(OutputSection *, OutputSection *)> comparator) {
llvm::stable_sort(sections, comparator);
}
const std::vector<OutputSection *> &getSections() const { return sections; }
size_t numNonHiddenSections() const;
uint64_t fileOff = 0;
StringRef name;
uint32_t maxProt = 0;
uint32_t initProt = 0;
uint8_t index;
private:
std::vector<OutputSection *> sections;
};
extern std::vector<OutputSegment *> outputSegments;
OutputSegment *getOrCreateOutputSegment(StringRef name);
} // namespace macho
} // namespace lld
#endif