Reapply [ELF] Only mark as DT_NEEDED libs that are strictly necessary (r219353)

When committed in r219353, this patch originally caused problems because it was
not tested in debug build. In such scenarios, Driver.cpp adds two additional
passes. These passes serialize all atoms via YAML and reads it back. Since the
patch changed ObjectAtom to hold a new reference, the serialization was removing
the extra data.

This commit implements r219853 in another way, similar to the original MIPS way,
by using a StringSet that holds the names of all copied atoms instead of
directly holding a reference to the copied atom. In this way, this commit is
simpler and eliminate the necessity of changing the DefinedAtom hierarchy to
hold a new data.

Reviewers: shankarke

http://reviews.llvm.org/D5713

llvm-svn: 219449

1 files changed, 11 insertions, 0 deletions

diff --git a/lld/lib/ReaderWriter/ELF/DefaultLayout.h b/lld/lib/ReaderWriter/ELF/DefaultLayout.h
index d198c5abc6f..87c6cfc1a29 100644
--- a/lld/lib/ReaderWriter/ELF/DefaultLayout.h
+++ b/lld/lib/ReaderWriter/ELF/DefaultLayout.h
@@ -10,6 +10,7 @@
 #ifndef LLD_READER_WRITER_ELF_DEFAULT_LAYOUT_H
 #define LLD_READER_WRITER_ELF_DEFAULT_LAYOUT_H
 
+#include "Atoms.h"
 #include "Chunk.h"
 #include "HeaderChunks.h"
 #include "Layout.h"
@@ -303,6 +304,10 @@ public:
     return _referencedDynAtoms.count(a);
   }
 
+  bool isCopied(const SharedLibraryAtom *sla) const {
+    return _copiedDynSymNames.count(sla->name());
+  }
+
 protected:
   /// \brief Allocate a new section.
   virtual AtomSection<ELFT> *createSection(
@@ -325,6 +330,7 @@ protected:
   LLD_UNIQUE_BUMP_PTR(RelocationTable<ELFT>) _pltRelocationTable;
   std::vector<lld::AtomLayout *> _absoluteAtoms;
   AtomSetT _referencedDynAtoms;
+  llvm::StringSet<> _copiedDynSymNames;
   const ELFLinkingContext &_context;
 };
 
@@ -582,6 +588,11 @@ ErrorOr<const lld::AtomLayout &> DefaultLayout<ELFT>::addAtom(const Atom *atom)
       if (isa<UndefinedAtom>(reloc->target()) && isLocalReloc)
         continue;
 
+      if (_context.isCopyRelocation(*reloc)) {
+        _copiedDynSymNames.insert(definedAtom->name());
+        continue;
+      }
+
       _referencedDynAtoms.insert(reloc->target());
     }