[mach-o] Add support for -sectalign option

The -sectalign option is used to increase the alignment required for a section.
It required some reworking of how the __TEXT segment is laid out because that
segment also contains the mach_header and load commands. And the size of load
commands depend on the number of segments, sections, and dependent dylibs used.

Using this option will simplify some future test cases because the final
address of code can be pinned down, making tests of its content easier.

llvm-svn: 214268

1 files changed, 13 insertions, 0 deletions

diff --git a/lld/include/lld/ReaderWriter/MachOLinkingContext.h b/lld/include/lld/ReaderWriter/MachOLinkingContext.h
index 82c782147ed..fe13aab7dbc 100644
--- a/lld/include/lld/ReaderWriter/MachOLinkingContext.h
+++ b/lld/include/lld/ReaderWriter/MachOLinkingContext.h
@@ -166,6 +166,12 @@ public:
     _existingPaths.insert(path);
   }
 
+  /// Add section alignment constraint on final layout.
+  void addSectionAlignment(StringRef seg, StringRef sect, uint8_t align2);
+
+  /// Returns true if specified section had alignment constraints.
+  bool sectionAligned(StringRef seg, StringRef sect, uint8_t &align2) const;
+
   StringRef dyldPath() const { return "/usr/lib/dyld"; }
 
   /// Stub creation Pass should be run.
@@ -201,6 +207,12 @@ private:
     uint32_t                  cpusubtype;
   };
 
+  struct SectionAlign {
+    StringRef segmentName;
+    StringRef sectionName;
+    uint8_t   align2;
+  };
+
   static ArchInfo _s_archInfos[];
 
   std::set<StringRef> _existingPaths; // For testing only.
@@ -222,6 +234,7 @@ private:
   StringRef _bundleLoader;
   mutable std::unique_ptr<mach_o::ArchHandler> _archHandler;
   mutable std::unique_ptr<Writer> _writer;
+  std::vector<SectionAlign> _sectAligns;
 };
 
 } // end namespace lld