--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lld/MachO/OutputSection.h	Mon May 25 11:55:54 2020 +0900
@@ -0,0 +1,109 @@
+//===- OutputSection.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_SECTION_H
+#define LLD_MACHO_OUTPUT_SECTION_H
+
+#include "lld/Common/LLVM.h"
+#include "llvm/ADT/DenseMap.h"
+
+namespace lld {
+namespace macho {
+
+class InputSection;
+class OutputSegment;
+
+// Output sections represent the finalized sections present within the final
+// linked executable. They can represent special sections (like the symbol
+// table), or represent coalesced sections from the various inputs given to the
+// linker with the same segment / section name.
+class OutputSection {
+public:
+  enum Kind {
+    MergedKind,
+    SyntheticKind,
+  };
+
+  OutputSection(Kind kind, StringRef name) : name(name), sectionKind(kind) {}
+  virtual ~OutputSection() = default;
+  Kind kind() const { return sectionKind; }
+
+  // These accessors will only be valid after finalizing the section.
+  uint64_t getSegmentOffset() const;
+
+  // How much space the section occupies in the address space.
+  virtual size_t getSize() const = 0;
+  // How much space the section occupies in the file. Most sections are copied
+  // as-is so their file size is the same as their address space size.
+  virtual uint64_t getFileSize() const { return getSize(); }
+
+  // Hidden sections omit header content, but body content may still be present.
+  virtual bool isHidden() const { return false; }
+  // Unneeded sections are omitted entirely (header and body).
+  virtual bool isNeeded() const { return true; }
+
+  // Some sections may allow coalescing other raw input sections.
+  virtual void mergeInput(InputSection *input);
+
+  // Specifically finalizes addresses and section size, not content.
+  virtual void finalize() {
+    // TODO investigate refactoring synthetic section finalization logic into
+    // overrides of this function.
+  }
+
+  virtual void writeTo(uint8_t *buf) const = 0;
+
+  StringRef name;
+  OutputSegment *parent = nullptr;
+
+  uint32_t index = 0;
+  uint64_t addr = 0;
+  uint64_t fileOff = 0;
+  uint32_t align = 1;
+  uint32_t flags = 0;
+
+private:
+  Kind sectionKind;
+};
+
+class OutputSectionComparator {
+public:
+  OutputSectionComparator(uint32_t segmentOrder,
+                          const std::vector<StringRef> &sectOrdering)
+      : segmentOrder(segmentOrder) {
+    for (uint32_t j = 0, m = sectOrdering.size(); j < m; ++j)
+      sectionOrdering[sectOrdering[j]] = j;
+  }
+
+  uint32_t sectionOrder(StringRef secname) {
+    auto sectIt = sectionOrdering.find(secname);
+    if (sectIt != sectionOrdering.end())
+      return sectIt->second;
+    return sectionOrdering.size();
+  }
+
+  // Sort sections within a common segment, which stores them in
+  // a MapVector of section name -> section
+  bool operator()(const std::pair<StringRef, OutputSection *> &a,
+                  const std::pair<StringRef, OutputSection *> &b) {
+    return sectionOrder(a.first) < sectionOrder(b.first);
+  }
+
+  bool operator<(const OutputSectionComparator &b) {
+    return segmentOrder < b.segmentOrder;
+  }
+
+private:
+  uint32_t segmentOrder;
+  llvm::DenseMap<StringRef, uint32_t> sectionOrdering;
+};
+
+} // namespace macho
+} // namespace lld
+
+#endif