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

12 files changed, 58 insertions, 36 deletions

diff --git a/lld/include/lld/ReaderWriter/ELFLinkingContext.h b/lld/include/lld/ReaderWriter/ELFLinkingContext.h
index 1ace8b93a07..582b345bc93 100644
--- a/lld/include/lld/ReaderWriter/ELFLinkingContext.h
+++ b/lld/include/lld/ReaderWriter/ELFLinkingContext.h
@@ -90,6 +90,15 @@ public:
                                    const Reference &) const {
     return false;
   }
+
+  /// \brief Is this a copy relocation?
+  ///
+  /// If this is a copy relocation, its target must be an ObjectAtom. We must
+  /// include in DT_NEEDED the name of the library where this object came from.
+  virtual bool isCopyRelocation(const Reference &) const {
+    return false;
+  }
+
   bool validateImpl(raw_ostream &diagnostics) override;
 
   /// \brief Does the linker allow dynamic libraries to be linked with?
diff --git a/lld/lib/ReaderWriter/ELF/AArch64/AArch64LinkingContext.h b/lld/lib/ReaderWriter/ELF/AArch64/AArch64LinkingContext.h
index 07ec6c1a2b3..2ae5b394556 100644
--- a/lld/lib/ReaderWriter/ELF/AArch64/AArch64LinkingContext.h
+++ b/lld/lib/ReaderWriter/ELF/AArch64/AArch64LinkingContext.h
@@ -59,6 +59,15 @@ public:
     }
   }
 
+  bool isCopyRelocation(const Reference &r) const override {
+    if (r.kindNamespace() != Reference::KindNamespace::ELF)
+      return false;
+    assert(r.kindArch() == Reference::KindArch::AArch64);
+    if (r.kindValue() == llvm::ELF::R_AARCH64_COPY)
+      return true;
+    return false;
+  }
+
   bool isPLTRelocation(const DefinedAtom &,
                                const Reference &r) const override {
     if (r.kindNamespace() != Reference::KindNamespace::ELF)
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());
     }
 
diff --git a/lld/lib/ReaderWriter/ELF/ExecutableWriter.h b/lld/lib/ReaderWriter/ELF/ExecutableWriter.h
index 5be96cc8f21..991fadb3665 100644
--- a/lld/lib/ReaderWriter/ELF/ExecutableWriter.h
+++ b/lld/lib/ReaderWriter/ELF/ExecutableWriter.h
@@ -35,6 +35,11 @@ protected:
   virtual bool createImplicitFiles(std::vector<std::unique_ptr<File> > &);
   virtual void finalizeDefaultAtomValues();
   virtual void createDefaultSections();
+
+  virtual bool isNeededTagRequired(const SharedLibraryAtom *sla) const {
+    return this->_layout.isCopied(sla);
+  }
+
   LLD_UNIQUE_BUMP_PTR(InterpSection<ELFT>) _interpSection;
   std::unique_ptr<CRuntimeFile<ELFT> > _runtimeFile;
 };
diff --git a/lld/lib/ReaderWriter/ELF/Mips/MipsDynamicLibraryWriter.h b/lld/lib/ReaderWriter/ELF/Mips/MipsDynamicLibraryWriter.h
index 5d895d52bc5..819c0869e7a 100644
--- a/lld/lib/ReaderWriter/ELF/Mips/MipsDynamicLibraryWriter.h
+++ b/lld/lib/ReaderWriter/ELF/Mips/MipsDynamicLibraryWriter.h
@@ -37,10 +37,6 @@ protected:
     return std::error_code();
   }
 
-  bool isNeededTagRequired(const SharedLibraryAtom *sla) const override {
-    return _writeHelper.isNeededTagRequired(sla);
-  }
-
   LLD_UNIQUE_BUMP_PTR(DynamicTable<ELFT>) createDynamicTable();
 
   LLD_UNIQUE_BUMP_PTR(DynamicSymbolTable<ELFT>) createDynamicSymbolTable();
diff --git a/lld/lib/ReaderWriter/ELF/Mips/MipsELFWriters.h b/lld/lib/ReaderWriter/ELF/Mips/MipsELFWriters.h
index 3b26816885a..4f4f22662fb 100644
--- a/lld/lib/ReaderWriter/ELF/Mips/MipsELFWriters.h
+++ b/lld/lib/ReaderWriter/ELF/Mips/MipsELFWriters.h
@@ -69,11 +69,6 @@ public:
     return file;
   }
 
-  bool isNeededTagRequired(const SharedLibraryAtom *sla) const {
-    return _targetLayout.isReferencedByDefinedAtom(sla) ||
-           _targetLayout.isCopied(sla);
-  }
-
 private:
   MipsLinkingContext &_ctx;
   MipsTargetLayout<ELFT> &_targetLayout;
diff --git a/lld/lib/ReaderWriter/ELF/Mips/MipsExecutableWriter.h b/lld/lib/ReaderWriter/ELF/Mips/MipsExecutableWriter.h
index a220428582b..07b155e7f47 100644
--- a/lld/lib/ReaderWriter/ELF/Mips/MipsExecutableWriter.h
+++ b/lld/lib/ReaderWriter/ELF/Mips/MipsExecutableWriter.h
@@ -38,10 +38,6 @@ protected:
     return std::error_code();
   }
 
-  bool isNeededTagRequired(const SharedLibraryAtom *sla) const override {
-    return _writeHelper.isNeededTagRequired(sla);
-  }
-
   LLD_UNIQUE_BUMP_PTR(DynamicTable<ELFT>) createDynamicTable();
 
   LLD_UNIQUE_BUMP_PTR(DynamicSymbolTable<ELFT>) createDynamicSymbolTable();
diff --git a/lld/lib/ReaderWriter/ELF/Mips/MipsLinkingContext.cpp b/lld/lib/ReaderWriter/ELF/Mips/MipsLinkingContext.cpp
index 946c96c7fa2..af3f8ad31cf 100644
--- a/lld/lib/ReaderWriter/ELF/Mips/MipsLinkingContext.cpp
+++ b/lld/lib/ReaderWriter/ELF/Mips/MipsLinkingContext.cpp
@@ -65,6 +65,15 @@ bool MipsLinkingContext::isDynamicRelocation(const DefinedAtom &,
   }
 }
 
+bool MipsLinkingContext::isCopyRelocation(const Reference &r) const {
+  if (r.kindNamespace() != Reference::KindNamespace::ELF)
+    return false;
+  assert(r.kindArch() == Reference::KindArch::Mips);
+  if (r.kindValue() == llvm::ELF::R_MIPS_COPY)
+    return true;
+  return false;
+}
+
 bool MipsLinkingContext::isPLTRelocation(const DefinedAtom &,
                                          const Reference &r) const {
   if (r.kindNamespace() != Reference::KindNamespace::ELF)
diff --git a/lld/lib/ReaderWriter/ELF/Mips/MipsLinkingContext.h b/lld/lib/ReaderWriter/ELF/Mips/MipsLinkingContext.h
index d39e403ccfc..ef8ff42b6d7 100644
--- a/lld/lib/ReaderWriter/ELF/Mips/MipsLinkingContext.h
+++ b/lld/lib/ReaderWriter/ELF/Mips/MipsLinkingContext.h
@@ -47,6 +47,7 @@ public:
   bool isRelaOutputFormat() const override { return false; }
   bool isDynamicRelocation(const DefinedAtom &,
                            const Reference &r) const override;
+  bool isCopyRelocation(const Reference &r) const override;
   bool isPLTRelocation(const DefinedAtom &, const Reference &r) const override;
 };
 
diff --git a/lld/lib/ReaderWriter/ELF/Mips/MipsTargetHandler.h b/lld/lib/ReaderWriter/ELF/Mips/MipsTargetHandler.h
index 1a3d6a3ebb3..04cc076fe62 100644
--- a/lld/lib/ReaderWriter/ELF/Mips/MipsTargetHandler.h
+++ b/lld/lib/ReaderWriter/ELF/Mips/MipsTargetHandler.h
@@ -62,26 +62,6 @@ public:
     }
   }
 
-  ErrorOr<const lld::AtomLayout &> addAtom(const Atom *atom) override {
-    // Maintain:
-    // 1. Set of shared library atoms referenced by regular defined atoms.
-    // 2. Set of shared library atoms have corresponding R_MIPS_COPY copies.
-    if (const auto *da = dyn_cast<DefinedAtom>(atom))
-      for (const Reference *ref : *da) {
-        if (ref->kindNamespace() == lld::Reference::KindNamespace::ELF) {
-          assert(ref->kindArch() == Reference::KindArch::Mips);
-          if (ref->kindValue() == llvm::ELF::R_MIPS_COPY)
-            _copiedDynSymNames.insert(atom->name());
-        }
-      }
-
-    return TargetLayout<ELFType>::addAtom(atom);
-  }
-
-  bool isCopied(const SharedLibraryAtom *sla) const {
-    return _copiedDynSymNames.count(sla->name());
-  }
-
   /// \brief GP offset relative to .got section.
   uint64_t getGPOffset() const { return 0x7FF0; }
 
@@ -109,7 +89,6 @@ private:
   MipsPLTSection<ELFType> *_pltSection;
   llvm::Optional<AtomLayout *> _gpAtom;
   llvm::Optional<AtomLayout *> _gpDispAtom;
-  llvm::StringSet<> _copiedDynSymNames;
 };
 
 /// \brief Mips Runtime file.
diff --git a/lld/lib/ReaderWriter/ELF/OutputELFWriter.h b/lld/lib/ReaderWriter/ELF/OutputELFWriter.h
index 30b1e573a66..dfb9a1a4a6e 100644
--- a/lld/lib/ReaderWriter/ELF/OutputELFWriter.h
+++ b/lld/lib/ReaderWriter/ELF/OutputELFWriter.h
@@ -116,7 +116,7 @@ protected:
 
   /// \brief Create DT_NEEDED dynamic tage for the shared library.
   virtual bool isNeededTagRequired(const SharedLibraryAtom *sla) const {
-    return true;
+    return false;
   }
 
   llvm::BumpPtrAllocator _alloc;
@@ -180,8 +180,11 @@ template <class ELFT>
 void OutputELFWriter<ELFT>::buildDynamicSymbolTable(const File &file) {
   ScopedTask task(getDefaultDomain(), "buildDynamicSymbolTable");
   for (const auto &sla : file.sharedLibrary()) {
-    if (isDynSymEntryRequired(sla))
+    if (isDynSymEntryRequired(sla)) {
       _dynamicSymbolTable->addSymbol(sla, ELF::SHN_UNDEF);
+      _soNeeded.insert(sla->loadName());
+      continue;
+    }
     if (isNeededTagRequired(sla))
       _soNeeded.insert(sla->loadName());
   }
diff --git a/lld/lib/ReaderWriter/ELF/X86_64/X86_64LinkingContext.h b/lld/lib/ReaderWriter/ELF/X86_64/X86_64LinkingContext.h
index a25c1eb4a59..4a40b33c00a 100644
--- a/lld/lib/ReaderWriter/ELF/X86_64/X86_64LinkingContext.h
+++ b/lld/lib/ReaderWriter/ELF/X86_64/X86_64LinkingContext.h
@@ -58,6 +58,15 @@ public:
     }
   }
 
+  bool isCopyRelocation(const Reference &r) const override {
+    if (r.kindNamespace() != Reference::KindNamespace::ELF)
+      return false;
+    assert(r.kindArch() == Reference::KindArch::x86_64);
+    if (r.kindValue() == llvm::ELF::R_X86_64_COPY)
+      return true;
+    return false;
+  }
+
   virtual bool isPLTRelocation(const DefinedAtom &,
                                const Reference &r) const override {
     if (r.kindNamespace() != Reference::KindNamespace::ELF)