Revert r360194 "[JITLink] Add support for MachO .alt_entry atoms."

The testcase is asserting on some bots - reverting while I investigate.

llvm-svn: 360200

3 files changed, 11 insertions, 110 deletions

diff --git a/llvm/lib/ExecutionEngine/JITLink/MachOAtomGraphBuilder.cpp b/llvm/lib/ExecutionEngine/JITLink/MachOAtomGraphBuilder.cpp
index 4054f66b5c1..670fc3ecf7a 100644
--- a/llvm/lib/ExecutionEngine/JITLink/MachOAtomGraphBuilder.cpp
+++ b/llvm/lib/ExecutionEngine/JITLink/MachOAtomGraphBuilder.cpp
@@ -44,33 +44,6 @@ void MachOAtomGraphBuilder::addCustomAtomizer(StringRef SectionName,
   CustomAtomizeFunctions[SectionName] = std::move(Atomizer);
 }
 
-bool MachOAtomGraphBuilder::areLayoutLocked(const Atom &A, const Atom &B) {
-  // If these atoms are the same then they're trivially "locked".
-  if (&A == &B)
-    return true;
-
-  // If A and B are different, check whether either is undefined. (in which
-  // case they are not locked).
-  if (!A.isDefined() || !B.isDefined())
-    return false;
-
-  // A and B are different, but they're both defined atoms. We need to check
-  // whether they're part of the same alt_entry chain.
-  auto &DA = static_cast<const DefinedAtom &>(A);
-  auto &DB = static_cast<const DefinedAtom &>(B);
-
-  auto AStartItr = AltEntryStarts.find(&DA);
-  if (AStartItr == AltEntryStarts.end()) // If A is not in a chain bail out.
-    return false;
-
-  auto BStartItr = AltEntryStarts.find(&DB);
-  if (BStartItr == AltEntryStarts.end()) // If B is not in a chain bail out.
-    return false;
-
-  // A and B are layout locked if they're in the same chain.
-  return AStartItr->second == BStartItr->second;
-}
-
 unsigned
 MachOAtomGraphBuilder::getPointerSize(const object::MachOObjectFile &Obj) {
   return Obj.is64Bit() ? 8 : 4;
@@ -153,9 +126,6 @@ Error MachOAtomGraphBuilder::addNonCustomAtoms() {
   DenseMap<MachOSection *, AddrToAtomMap> SecToAtoms;
 
   DenseMap<MachOSection *, unsigned> FirstOrdinal;
-  std::vector<DefinedAtom *> AltEntryAtoms;
-
-  DenseSet<StringRef> ProcessedSymbols; // Used to check for duplicate defs.
 
   for (auto SymI = Obj.symbol_begin(), SymE = Obj.symbol_end(); SymI != SymE;
        ++SymI) {
@@ -165,14 +135,6 @@ Error MachOAtomGraphBuilder::addNonCustomAtoms() {
     if (!Name)
       return Name.takeError();
 
-    // Bail out on duplicate definitions: There should never be more than one
-    // definition for a symbol in a given object file.
-    if (ProcessedSymbols.count(*Name))
-      return make_error<JITLinkError>("Duplicate definition within object: " +
-                                      *Name);
-    else
-      ProcessedSymbols.insert(*Name);
-
     auto Addr = Sym.getAddress();
     if (!Addr)
       return Addr.takeError();
@@ -227,35 +189,24 @@ Error MachOAtomGraphBuilder::addNonCustomAtoms() {
 
     auto &Sec = SecByIndexItr->second;
 
-    auto &DA = G->addDefinedAtom(Sec.getGenericSection(), *Name, *Addr,
-                                 std::max(Sym.getAlignment(), 1U));
-
-    DA.setGlobal(Flags & object::SymbolRef::SF_Global);
-    DA.setExported(Flags & object::SymbolRef::SF_Exported);
-    DA.setWeak(Flags & object::SymbolRef::SF_Weak);
+    auto &A = G->addDefinedAtom(Sec.getGenericSection(), *Name, *Addr,
+                                std::max(Sym.getAlignment(), 1U));
 
-    DA.setCallable(*SymType & object::SymbolRef::ST_Function);
+    A.setGlobal(Flags & object::SymbolRef::SF_Global);
+    A.setExported(Flags & object::SymbolRef::SF_Exported);
+    A.setWeak(Flags & object::SymbolRef::SF_Weak);
 
-    // Check alt-entry.
-    {
-      uint16_t NDesc = 0;
-      if (Obj.is64Bit())
-        NDesc = Obj.getSymbolTableEntry(SymI->getRawDataRefImpl()).n_desc;
-      else
-        NDesc = Obj.getSymbolTableEntry(SymI->getRawDataRefImpl()).n_desc;
-      if (NDesc & MachO::N_ALT_ENTRY)
-        AltEntryAtoms.push_back(&DA);
-    }
+    A.setCallable(*SymType & object::SymbolRef::ST_Function);
 
     LLVM_DEBUG({
       dbgs() << "  Added " << *Name
              << " addr: " << format("0x%016" PRIx64, *Addr)
-             << ", align: " << DA.getAlignment()
+             << ", align: " << A.getAlignment()
              << ", section: " << Sec.getGenericSection().getName() << "\n";
     });
 
     auto &SecAtoms = SecToAtoms[&Sec];
-    SecAtoms[DA.getAddress() - Sec.getAddress()] = &DA;
+    SecAtoms[A.getAddress() - Sec.getAddress()] = &A;
   }
 
   // Add anonymous atoms.
@@ -312,50 +263,6 @@ Error MachOAtomGraphBuilder::addNonCustomAtoms() {
     }
   }
 
-  LLVM_DEBUG(dbgs() << "Adding alt-entry starts\n");
-
-  // Sort alt-entry atoms by address in ascending order.
-  llvm::sort(AltEntryAtoms.begin(), AltEntryAtoms.end(),
-             [](const DefinedAtom *LHS, const DefinedAtom *RHS) {
-               return LHS->getAddress() < RHS->getAddress();
-             });
-
-  // Process alt-entry atoms in address order to build the table of alt-entry
-  // atoms to alt-entry chain starts.
-  for (auto *DA : AltEntryAtoms) {
-    assert(!AltEntryStarts.count(DA) && "Duplicate entry in AltEntryStarts");
-
-    // DA is an alt-entry atom. Look for the predecessor atom that it is locked
-    // to, bailing out if we do not find one.
-    auto AltEntryPred = G->findAtomByAddress(DA->getAddress() - 1);
-    if (!AltEntryPred)
-      return AltEntryPred.takeError();
-
-    // Add a LayoutNext edge from the predecessor to this atom.
-    AltEntryPred->addEdge(Edge::LayoutNext, 0, *DA, 0);
-
-    // Check to see whether the predecessor itself is an alt-entry atom.
-    auto AltEntryStartItr = AltEntryStarts.find(&*AltEntryPred);
-    if (AltEntryStartItr != AltEntryStarts.end()) {
-      // If the predecessor was an alt-entry atom then re-use its value.
-      AltEntryStarts[DA] = AltEntryStartItr->second;
-      LLVM_DEBUG({
-        dbgs() << "  " << *DA << " -> " << *AltEntryStartItr->second
-               << " (based on existing entry for " << *AltEntryPred << ")\n";
-      });
-    } else {
-      // If the predecessor does not have an entry then add an entry for this
-      // atom (i.e. the alt_entry atom) and a self-reference entry for the
-      /// predecessory atom that is the start of this chain.
-      AltEntryStarts[&*AltEntryPred] = &*AltEntryPred;
-      AltEntryStarts[DA] = &*AltEntryPred;
-      LLVM_DEBUG({
-        dbgs() << "  " << *AltEntryPred << " -> " << *AltEntryPred << "\n"
-               << "  " << *DA << " -> " << *AltEntryPred << "\n";
-      });
-    }
-  }
-
   return Error::success();
 }
 
diff --git a/llvm/lib/ExecutionEngine/JITLink/MachOAtomGraphBuilder.h b/llvm/lib/ExecutionEngine/JITLink/MachOAtomGraphBuilder.h
index 540e2c366f0..340a11dfc0e 100644
--- a/llvm/lib/ExecutionEngine/JITLink/MachOAtomGraphBuilder.h
+++ b/llvm/lib/ExecutionEngine/JITLink/MachOAtomGraphBuilder.h
@@ -96,10 +96,6 @@ protected:
 
   virtual Error addRelocations() = 0;
 
-  /// Returns true if Atom A and Atom B are at a fixed offset from one another
-  /// (i.e. if they're part of the same alt-entry chain).
-  bool areLayoutLocked(const Atom &A, const Atom &B);
-
 private:
   static unsigned getPointerSize(const object::MachOObjectFile &Obj);
   static support::endianness getEndianness(const object::MachOObjectFile &Obj);
@@ -112,7 +108,6 @@ private:
 
   const object::MachOObjectFile &Obj;
   std::unique_ptr<AtomGraph> G;
-  DenseMap<const DefinedAtom *, const DefinedAtom *> AltEntryStarts;
   DenseMap<unsigned, MachOSection> Sections;
   StringMap<CustomAtomizeFunction> CustomAtomizeFunctions;
   Optional<MachOSection> CommonSymbolsSection;
diff --git a/llvm/lib/ExecutionEngine/JITLink/MachO_x86_64.cpp b/llvm/lib/ExecutionEngine/JITLink/MachO_x86_64.cpp
index d9472e40ead..75725dbc526 100644
--- a/llvm/lib/ExecutionEngine/JITLink/MachO_x86_64.cpp
+++ b/llvm/lib/ExecutionEngine/JITLink/MachO_x86_64.cpp
@@ -181,20 +181,19 @@ private:
     MachOX86RelocationKind DeltaKind;
     Atom *TargetAtom;
     uint64_t Addend;
-    if (areLayoutLocked(AtomToFix, *FromAtom)) {
+    if (&AtomToFix == &*FromAtom) {
       TargetAtom = ToAtom;
       DeltaKind = (SubRI.r_length == 3) ? Delta64 : Delta32;
       Addend = FixupValue + (FixupAddress - FromAtom->getAddress());
       // FIXME: handle extern 'from'.
-    } else if (areLayoutLocked(AtomToFix, *ToAtom)) {
+    } else if (&AtomToFix == ToAtom) {
       TargetAtom = &*FromAtom;
       DeltaKind = (SubRI.r_length == 3) ? NegDelta64 : NegDelta32;
       Addend = FixupValue - (FixupAddress - ToAtom->getAddress());
     } else {
       // AtomToFix was neither FromAtom nor ToAtom.
       return make_error<JITLinkError>("SUBTRACTOR relocation must fix up "
-                                      "either 'A' or 'B' (or an atom in one "
-                                      "of their alt-entry groups)");
+                                      "either 'A' or 'B'");
     }
 
     return PairRelocInfo(DeltaKind, TargetAtom, Addend);