diff --git a/include/llvm/ExecutionEngine/ExecutionEngine.h b/include/llvm/ExecutionEngine/ExecutionEngine.h
index 77c23b46d32..7932688290e 100644
--- a/include/llvm/ExecutionEngine/ExecutionEngine.h
+++ b/include/llvm/ExecutionEngine/ExecutionEngine.h
@@ -137,17 +137,15 @@ protected:
   virtual char *getMemoryForGV(const GlobalVariable *GV);
 
   static ExecutionEngine *(*MCJITCtor)(
-                                std::unique_ptr<Module> M,
-                                std::string *ErrorStr,
-                                std::shared_ptr<MCJITMemoryManager> MM,
-                                std::shared_ptr<JITSymbolResolver> SR,
-                                std::unique_ptr<TargetMachine> TM);
+      std::unique_ptr<Module> M, std::string *ErrorStr,
+      std::shared_ptr<MCJITMemoryManager> MM,
+      std::shared_ptr<LegacyJITSymbolResolver> SR,
+      std::unique_ptr<TargetMachine> TM);
 
   static ExecutionEngine *(*OrcMCJITReplacementCtor)(
-                                std::string *ErrorStr,
-                                std::shared_ptr<MCJITMemoryManager> MM,
-                                std::shared_ptr<JITSymbolResolver> SR,
-                                std::unique_ptr<TargetMachine> TM);
+      std::string *ErrorStr, std::shared_ptr<MCJITMemoryManager> MM,
+      std::shared_ptr<LegacyJITSymbolResolver> SR,
+      std::unique_ptr<TargetMachine> TM);
 
   static ExecutionEngine *(*InterpCtor)(std::unique_ptr<Module> M,
                                         std::string *ErrorStr);
@@ -532,7 +530,7 @@ private:
   std::string *ErrorStr;
   CodeGenOpt::Level OptLevel;
   std::shared_ptr<MCJITMemoryManager> MemMgr;
-  std::shared_ptr<JITSymbolResolver> Resolver;
+  std::shared_ptr<LegacyJITSymbolResolver> Resolver;
   TargetOptions Options;
   Optional<Reloc::Model> RelocModel;
   Optional<CodeModel::Model> CMModel;
@@ -571,8 +569,7 @@ public:
   EngineBuilder&
   setMemoryManager(std::unique_ptr<MCJITMemoryManager> MM);
 
-  EngineBuilder&
-  setSymbolResolver(std::unique_ptr<JITSymbolResolver> SR);
+  EngineBuilder &setSymbolResolver(std::unique_ptr<LegacyJITSymbolResolver> SR);
 
   /// setErrorStr - Set the error string to write to on error.  This option
   /// defaults to NULL.
diff --git a/include/llvm/ExecutionEngine/JITSymbol.h b/include/llvm/ExecutionEngine/JITSymbol.h
index d171f998e6f..6aba236b619 100644
--- a/include/llvm/ExecutionEngine/JITSymbol.h
+++ b/include/llvm/ExecutionEngine/JITSymbol.h
@@ -19,8 +19,11 @@
 #include <cstddef>
 #include <cstdint>
 #include <functional>
+#include <map>
+#include <set>
 #include <string>
 
+#include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Error.h"
 
 namespace llvm {
@@ -269,11 +272,50 @@ private:
   JITSymbolFlags Flags;
 };
 
-/// \brief Symbol resolution.
+/// @brief Symbol resolution interface.
+///
+/// Allows symbol flags and addresses to be looked up by name.
+/// Symbol queries are done in bulk (i.e. you request resolution of a set of
+/// symbols, rather than a single one) to reduce IPC overhead in the case of
+/// remote JITing, and expose opportunities for parallel compilation.
 class JITSymbolResolver {
 public:
+  using SymbolNameSet = std::set<StringRef>;
+  using LookupResult = std::map<StringRef, JITEvaluatedSymbol>;
+  using LookupFlagsResult = std::map<StringRef, JITSymbolFlags>;
+
   virtual ~JITSymbolResolver() = default;
 
+  /// @brief Returns the fully resolved address and flags for each of the given
+  ///        symbols.
+  ///
+  /// This method will return an error if any of the given symbols can not be
+  /// resolved, or if the resolution process itself triggers an error.
+  virtual Expected<LookupResult> lookup(const SymbolNameSet &Symbols) = 0;
+
+  /// @brief Returns the symbol flags for each of the given symbols.
+  ///
+  /// This method does NOT return an error if any of the given symbols is
+  /// missing. Instead, that symbol will be left out of the result map.
+  virtual Expected<LookupFlagsResult>
+  lookupFlags(const SymbolNameSet &Symbols) = 0;
+
+private:
+  virtual void anchor();
+};
+
+/// \brief Legacy symbol resolution interface.
+class LegacyJITSymbolResolver : public JITSymbolResolver {
+public:
+  /// @brief Performs lookup by, for each symbol, first calling
+  ///        findSymbolInLogicalDylib and if that fails calling
+  ///        findSymbol.
+  Expected<LookupResult> lookup(const SymbolNameSet &Symbols) final;
+
+  /// @brief Performs flags lookup by calling findSymbolInLogicalDylib and
+  ///        returning the flags value for that symbol.
+  Expected<LookupFlagsResult> lookupFlags(const SymbolNameSet &Symbols) final;
+
   /// This method returns the address of the specified symbol if it exists
   /// within the logical dynamic library represented by this JITSymbolResolver.
   /// Unlike findSymbol, queries through this interface should return addresses
diff --git a/include/llvm/ExecutionEngine/Orc/CompileOnDemandLayer.h b/include/llvm/ExecutionEngine/Orc/CompileOnDemandLayer.h
index a961992c214..3281c354676 100644
--- a/include/llvm/ExecutionEngine/Orc/CompileOnDemandLayer.h
+++ b/include/llvm/ExecutionEngine/Orc/CompileOnDemandLayer.h
@@ -183,7 +183,7 @@ private:
       return Error::success();
     }
 
-    std::shared_ptr<JITSymbolResolver> ExternalSymbolResolver;
+    std::shared_ptr<LegacyJITSymbolResolver> ExternalSymbolResolver;
     std::unique_ptr<IndirectStubsMgrT> StubsMgr;
     StaticGlobalRenamer StaticRenamer;
     SourceModulesList SourceModules;
@@ -223,7 +223,7 @@ public:
   /// @brief Add a module to the compile-on-demand layer.
   Expected<ModuleHandleT>
   addModule(std::shared_ptr<Module> M,
-            std::shared_ptr<JITSymbolResolver> Resolver) {
+            std::shared_ptr<LegacyJITSymbolResolver> Resolver) {
 
     LogicalDylibs.push_back(LogicalDylib());
     auto &LD = LogicalDylibs.back();
diff --git a/include/llvm/ExecutionEngine/Orc/LambdaResolver.h b/include/llvm/ExecutionEngine/Orc/LambdaResolver.h
index 228392ae0d4..7b6f3d2f92a 100644
--- a/include/llvm/ExecutionEngine/Orc/LambdaResolver.h
+++ b/include/llvm/ExecutionEngine/Orc/LambdaResolver.h
@@ -23,7 +23,7 @@ namespace llvm {
 namespace orc {
 
 template <typename DylibLookupFtorT, typename ExternalLookupFtorT>
-class LambdaResolver : public JITSymbolResolver {
+class LambdaResolver : public LegacyJITSymbolResolver {
 public:
   LambdaResolver(DylibLookupFtorT DylibLookupFtor,
                  ExternalLookupFtorT ExternalLookupFtor)
diff --git a/include/llvm/ExecutionEngine/Orc/NullResolver.h b/include/llvm/ExecutionEngine/Orc/NullResolver.h
index 957b94912b3..fc5cb3e7c71 100644
--- a/include/llvm/ExecutionEngine/Orc/NullResolver.h
+++ b/include/llvm/ExecutionEngine/Orc/NullResolver.h
@@ -22,7 +22,7 @@ namespace orc {
 
 /// SymbolResolver impliementation that rejects all resolution requests.
 /// Useful for clients that have no cross-object fixups.
-class NullResolver : public JITSymbolResolver {
+class NullResolver : public LegacyJITSymbolResolver {
 public:
   JITSymbol findSymbol(const std::string &Name) final;
 
diff --git a/include/llvm/ExecutionEngine/Orc/RemoteObjectLayer.h b/include/llvm/ExecutionEngine/Orc/RemoteObjectLayer.h
index 17255954a99..21d0b68a771 100644
--- a/include/llvm/ExecutionEngine/Orc/RemoteObjectLayer.h
+++ b/include/llvm/ExecutionEngine/Orc/RemoteObjectLayer.h
@@ -328,7 +328,8 @@ public:
   /// @return A handle that can be used to refer to the loaded object (for
   ///         symbol searching, finalization, freeing memory, etc.).
   Expected<ObjHandleT>
-  addObject(ObjectPtr Object, std::shared_ptr<JITSymbolResolver> Resolver) {
+  addObject(ObjectPtr Object,
+            std::shared_ptr<LegacyJITSymbolResolver> Resolver) {
     StringRef ObjBuffer = Object->getBinary()->getData();
     if (auto HandleOrErr =
           this->Remote.template callB<AddObject>(ObjBuffer)) {
@@ -386,7 +387,8 @@ private:
   }
 
   std::map<remote::ResourceIdMgr::ResourceId,
-           std::shared_ptr<JITSymbolResolver>> Resolvers;
+           std::shared_ptr<LegacyJITSymbolResolver>>
+      Resolvers;
 };
 
 /// RemoteObjectServerLayer acts as a server and handling RPC calls for the
diff --git a/include/llvm/ExecutionEngine/RTDyldMemoryManager.h b/include/llvm/ExecutionEngine/RTDyldMemoryManager.h
index 0c1862c5c3e..ee75202d2b6 100644
--- a/include/llvm/ExecutionEngine/RTDyldMemoryManager.h
+++ b/include/llvm/ExecutionEngine/RTDyldMemoryManager.h
@@ -56,7 +56,7 @@ public:
 // FIXME: As the RuntimeDyld fills out, additional routines will be needed
 //        for the varying types of objects to be allocated.
 class RTDyldMemoryManager : public MCJITMemoryManager,
-                            public JITSymbolResolver {
+                            public LegacyJITSymbolResolver {
 public:
   RTDyldMemoryManager() = default;
   RTDyldMemoryManager(const RTDyldMemoryManager&) = delete;
diff --git a/lib/ExecutionEngine/ExecutionEngine.cpp b/lib/ExecutionEngine/ExecutionEngine.cpp
index 233ece29422..e4efc15f2ae 100644
--- a/lib/ExecutionEngine/ExecutionEngine.cpp
+++ b/lib/ExecutionEngine/ExecutionEngine.cpp
@@ -49,14 +49,13 @@ STATISTIC(NumGlobals  , "Number of global vars initialized");
 ExecutionEngine *(*ExecutionEngine::MCJITCtor)(
     std::unique_ptr<Module> M, std::string *ErrorStr,
     std::shared_ptr<MCJITMemoryManager> MemMgr,
-
-    std::shared_ptr<JITSymbolResolver> Resolver,
+    std::shared_ptr<LegacyJITSymbolResolver> Resolver,
     std::unique_ptr<TargetMachine> TM) = nullptr;
 
 ExecutionEngine *(*ExecutionEngine::OrcMCJITReplacementCtor)(
-  std::string *ErrorStr, std::shared_ptr<MCJITMemoryManager> MemMgr,
-  std::shared_ptr<JITSymbolResolver> Resolver,
-  std::unique_ptr<TargetMachine> TM) = nullptr;
+    std::string *ErrorStr, std::shared_ptr<MCJITMemoryManager> MemMgr,
+    std::shared_ptr<LegacyJITSymbolResolver> Resolver,
+    std::unique_ptr<TargetMachine> TM) = nullptr;
 
 ExecutionEngine *(*ExecutionEngine::InterpCtor)(std::unique_ptr<Module> M,
                                                 std::string *ErrorStr) =nullptr;
@@ -502,9 +501,9 @@ EngineBuilder::setMemoryManager(std::unique_ptr<MCJITMemoryManager> MM) {
   return *this;
 }
 
-EngineBuilder&
-EngineBuilder::setSymbolResolver(std::unique_ptr<JITSymbolResolver> SR) {
-  Resolver = std::shared_ptr<JITSymbolResolver>(std::move(SR));
+EngineBuilder &
+EngineBuilder::setSymbolResolver(std::unique_ptr<LegacyJITSymbolResolver> SR) {
+  Resolver = std::shared_ptr<LegacyJITSymbolResolver>(std::move(SR));
   return *this;
 }
 
diff --git a/lib/ExecutionEngine/MCJIT/MCJIT.cpp b/lib/ExecutionEngine/MCJIT/MCJIT.cpp
index f7b8a3b657e..438e656b60f 100644
--- a/lib/ExecutionEngine/MCJIT/MCJIT.cpp
+++ b/lib/ExecutionEngine/MCJIT/MCJIT.cpp
@@ -39,11 +39,10 @@ static struct RegisterJIT {
 extern "C" void LLVMLinkInMCJIT() {
 }
 
-ExecutionEngine*
-MCJIT::createJIT(std::unique_ptr<Module> M,
-                 std::string *ErrorStr,
+ExecutionEngine *
+MCJIT::createJIT(std::unique_ptr<Module> M, std::string *ErrorStr,
                  std::shared_ptr<MCJITMemoryManager> MemMgr,
-                 std::shared_ptr<JITSymbolResolver> Resolver,
+                 std::shared_ptr<LegacyJITSymbolResolver> Resolver,
                  std::unique_ptr<TargetMachine> TM) {
   // Try to register the program as a source of symbols to resolve against.
   //
@@ -64,7 +63,7 @@ MCJIT::createJIT(std::unique_ptr<Module> M,
 
 MCJIT::MCJIT(std::unique_ptr<Module> M, std::unique_ptr<TargetMachine> TM,
              std::shared_ptr<MCJITMemoryManager> MemMgr,
-             std::shared_ptr<JITSymbolResolver> Resolver)
+             std::shared_ptr<LegacyJITSymbolResolver> Resolver)
     : ExecutionEngine(TM->createDataLayout(), std::move(M)), TM(std::move(TM)),
       Ctx(nullptr), MemMgr(std::move(MemMgr)),
       Resolver(*this, std::move(Resolver)), Dyld(*this->MemMgr, this->Resolver),
diff --git a/lib/ExecutionEngine/MCJIT/MCJIT.h b/lib/ExecutionEngine/MCJIT/MCJIT.h
index daf578f5daa..110cfa675cf 100644
--- a/lib/ExecutionEngine/MCJIT/MCJIT.h
+++ b/lib/ExecutionEngine/MCJIT/MCJIT.h
@@ -26,11 +26,11 @@ class MCJIT;
 // functions across modules that it owns.  It aggregates the memory manager
 // that is passed in to the MCJIT constructor and defers most functionality
 // to that object.
-class LinkingSymbolResolver : public JITSymbolResolver {
+class LinkingSymbolResolver : public LegacyJITSymbolResolver {
 public:
   LinkingSymbolResolver(MCJIT &Parent,
-                        std::shared_ptr<JITSymbolResolver> Resolver)
-    : ParentEngine(Parent), ClientResolver(std::move(Resolver)) {}
+                        std::shared_ptr<LegacyJITSymbolResolver> Resolver)
+      : ParentEngine(Parent), ClientResolver(std::move(Resolver)) {}
 
   JITSymbol findSymbol(const std::string &Name) override;
 
@@ -41,7 +41,7 @@ public:
 
 private:
   MCJIT &ParentEngine;
-  std::shared_ptr<JITSymbolResolver> ClientResolver;
+  std::shared_ptr<LegacyJITSymbolResolver> ClientResolver;
 };
 
 // About Module states: added->loaded->finalized.
@@ -67,7 +67,7 @@ private:
 class MCJIT : public ExecutionEngine {
   MCJIT(std::unique_ptr<Module> M, std::unique_ptr<TargetMachine> tm,
         std::shared_ptr<MCJITMemoryManager> MemMgr,
-        std::shared_ptr<JITSymbolResolver> Resolver);
+        std::shared_ptr<LegacyJITSymbolResolver> Resolver);
 
   typedef llvm::SmallPtrSet<Module *, 4> ModulePtrSet;
 
@@ -300,11 +300,10 @@ public:
     MCJITCtor = createJIT;
   }
 
-  static ExecutionEngine*
-  createJIT(std::unique_ptr<Module> M,
-            std::string *ErrorStr,
+  static ExecutionEngine *
+  createJIT(std::unique_ptr<Module> M, std::string *ErrorStr,
             std::shared_ptr<MCJITMemoryManager> MemMgr,
-            std::shared_ptr<JITSymbolResolver> Resolver,
+            std::shared_ptr<LegacyJITSymbolResolver> Resolver,
             std::unique_ptr<TargetMachine> TM);
 
   // @}
diff --git a/lib/ExecutionEngine/Orc/OrcCBindingsStack.h b/lib/ExecutionEngine/Orc/OrcCBindingsStack.h
index 405970e063d..05b1f47eb5b 100644
--- a/lib/ExecutionEngine/Orc/OrcCBindingsStack.h
+++ b/lib/ExecutionEngine/Orc/OrcCBindingsStack.h
@@ -196,7 +196,7 @@ public:
     return mapError(IndirectStubsMgr->updatePointer(Name, Addr));
   }
 
-  std::shared_ptr<JITSymbolResolver>
+  std::shared_ptr<LegacyJITSymbolResolver>
   createResolver(LLVMOrcSymbolResolverFn ExternalResolver,
                  void *ExternalResolverCtx) {
     return orc::createLambdaResolver(
diff --git a/lib/ExecutionEngine/Orc/OrcMCJITReplacement.h b/lib/ExecutionEngine/Orc/OrcMCJITReplacement.h
index 1dc8d4ac7bc..166d1369c72 100644
--- a/lib/ExecutionEngine/Orc/OrcMCJITReplacement.h
+++ b/lib/ExecutionEngine/Orc/OrcMCJITReplacement.h
@@ -138,7 +138,7 @@ class OrcMCJITReplacement : public ExecutionEngine {
     std::shared_ptr<MCJITMemoryManager> ClientMM;
   };
 
-  class LinkingResolver : public JITSymbolResolver {
+  class LinkingResolver : public LegacyJITSymbolResolver {
   public:
     LinkingResolver(OrcMCJITReplacement &M) : M(M) {}
 
@@ -160,20 +160,19 @@ private:
   static ExecutionEngine *
   createOrcMCJITReplacement(std::string *ErrorMsg,
                             std::shared_ptr<MCJITMemoryManager> MemMgr,
-                            std::shared_ptr<JITSymbolResolver> Resolver,
+                            std::shared_ptr<LegacyJITSymbolResolver> Resolver,
                             std::unique_ptr<TargetMachine> TM) {
     return new OrcMCJITReplacement(std::move(MemMgr), std::move(Resolver),
                                    std::move(TM));
   }
 
 public:
-  OrcMCJITReplacement(
-      std::shared_ptr<MCJITMemoryManager> MemMgr,
-      std::shared_ptr<JITSymbolResolver> ClientResolver,
-      std::unique_ptr<TargetMachine> TM)
+  OrcMCJITReplacement(std::shared_ptr<MCJITMemoryManager> MemMgr,
+                      std::shared_ptr<LegacyJITSymbolResolver> ClientResolver,
+                      std::unique_ptr<TargetMachine> TM)
       : ExecutionEngine(TM->createDataLayout()), TM(std::move(TM)),
-        MemMgr(std::make_shared<MCJITReplacementMemMgr>(*this,
-                                                        std::move(MemMgr))),
+        MemMgr(
+            std::make_shared<MCJITReplacementMemMgr>(*this, std::move(MemMgr))),
         Resolver(std::make_shared<LinkingResolver>(*this)),
         ClientResolver(std::move(ClientResolver)), NotifyObjectLoaded(*this),
         NotifyFinalized(*this),
@@ -378,7 +377,7 @@ private:
   std::unique_ptr<TargetMachine> TM;
   std::shared_ptr<MCJITReplacementMemMgr> MemMgr;
   std::shared_ptr<LinkingResolver> Resolver;
-  std::shared_ptr<JITSymbolResolver> ClientResolver;
+  std::shared_ptr<LegacyJITSymbolResolver> ClientResolver;
   Mangler Mang;
 
   // IMPORTANT: ShouldDelete *must* come before LocalModules: The shared_ptr
diff --git a/lib/ExecutionEngine/RuntimeDyld/JITSymbol.cpp b/lib/ExecutionEngine/RuntimeDyld/JITSymbol.cpp
index 87059ef2b88..670c6d2fa3f 100644
--- a/lib/ExecutionEngine/RuntimeDyld/JITSymbol.cpp
+++ b/lib/ExecutionEngine/RuntimeDyld/JITSymbol.cpp
@@ -47,3 +47,53 @@ ARMJITSymbolFlags llvm::ARMJITSymbolFlags::fromObjectSymbol(
     Flags |= ARMJITSymbolFlags::Thumb;
   return Flags;
 }
+
+/// @brief Performs lookup by, for each symbol, first calling
+///        findSymbolInLogicalDylib and if that fails calling
+///        findSymbol.
+Expected<JITSymbolResolver::LookupResult>
+LegacyJITSymbolResolver::lookup(const SymbolNameSet &Symbols) {
+  JITSymbolResolver::LookupResult Result;
+  for (auto &Symbol : Symbols) {
+    std::string SymName = Symbol.str();
+    if (auto Sym = findSymbolInLogicalDylib(SymName)) {
+      if (auto AddrOrErr = Sym.getAddress())
+        Result[Symbol] = JITEvaluatedSymbol(*AddrOrErr, Sym.getFlags());
+      else
+        return AddrOrErr.takeError();
+    } else if (auto Err = Sym.takeError())
+      return std::move(Err);
+    else {
+      // findSymbolInLogicalDylib failed. Lets try findSymbol.
+      if (auto Sym = findSymbol(SymName)) {
+        if (auto AddrOrErr = Sym.getAddress())
+          Result[Symbol] = JITEvaluatedSymbol(*AddrOrErr, Sym.getFlags());
+        else
+          return AddrOrErr.takeError();
+      } else if (auto Err = Sym.takeError())
+        return std::move(Err);
+      else
+        return make_error<StringError>("Symbol not found: " + Symbol,
+                                       inconvertibleErrorCode());
+    }
+  }
+
+  return std::move(Result);
+}
+
+/// @brief Performs flags lookup by calling findSymbolInLogicalDylib and
+///        returning the flags value for that symbol.
+Expected<JITSymbolResolver::LookupFlagsResult>
+LegacyJITSymbolResolver::lookupFlags(const SymbolNameSet &Symbols) {
+  JITSymbolResolver::LookupFlagsResult Result;
+
+  for (auto &Symbol : Symbols) {
+    std::string SymName = Symbol.str();
+    if (auto Sym = findSymbolInLogicalDylib(SymName))
+      Result[Symbol] = Sym.getFlags();
+    else if (auto Err = Sym.takeError())
+      return std::move(Err);
+  }
+
+  return std::move(Result);
+}
diff --git a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
index 3a025f4c026..ce8d480a408 100644
--- a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
+++ b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
@@ -202,7 +202,33 @@ RuntimeDyldImpl::loadObjectImpl(const object::ObjectFile &Obj) {
   ObjSectionToIDMap LocalSections;
 
   // Common symbols requiring allocation, with their sizes and alignments
-  CommonSymbolList CommonSymbols;
+  CommonSymbolList CommonSymbolsToAllocate;
+
+  uint64_t CommonSize = 0;
+  uint32_t CommonAlign = 0;
+
+  // First, collect all weak and common symbols. We need to know if stronger
+  // definitions occur elsewhere.
+  JITSymbolResolver::LookupFlagsResult SymbolFlags;
+  {
+    JITSymbolResolver::SymbolNameSet Symbols;
+    for (auto &Sym : Obj.symbols()) {
+      uint32_t Flags = Sym.getFlags();
+      if ((Flags & SymbolRef::SF_Common) || (Flags & SymbolRef::SF_Weak)) {
+        // Get symbol name.
+        StringRef Name;
+        if (auto NameOrErr = Sym.getName())
+          Symbols.insert(*NameOrErr);
+        else
+          return NameOrErr.takeError();
+      }
+    }
+
+    if (auto FlagsResultOrErr = Resolver.lookupFlags(Symbols))
+      SymbolFlags = std::move(*FlagsResultOrErr);
+    else
+      return FlagsResultOrErr.takeError();
+  }
 
   // Parse symbols
   DEBUG(dbgs() << "Parse symbols:\n");
@@ -214,102 +240,108 @@ RuntimeDyldImpl::loadObjectImpl(const object::ObjectFile &Obj) {
     if (Flags & SymbolRef::SF_Undefined)
       continue;
 
-    if (Flags & SymbolRef::SF_Common)
-      CommonSymbols.push_back(*I);
-    else {
+    // Get the symbol type.
+    object::SymbolRef::Type SymType;
+    if (auto SymTypeOrErr = I->getType())
+      SymType = *SymTypeOrErr;
+    else
+      return SymTypeOrErr.takeError();
 
-      // Get the symbol type.
-      object::SymbolRef::Type SymType;
-      if (auto SymTypeOrErr = I->getType())
-        SymType =  *SymTypeOrErr;
+    // Get symbol name.
+    StringRef Name;
+    if (auto NameOrErr = I->getName())
+      Name = *NameOrErr;
+    else
+      return NameOrErr.takeError();
+
+    // Compute JIT symbol flags.
+    JITSymbolFlags JITSymFlags = getJITSymbolFlags(*I);
+
+    // If this is a weak definition, check to see if there's a strong one.
+    // If there is, skip this symbol (we won't be providing it: the strong
+    // definition will). If there's no strong definition, make this definition
+    // strong.
+    if (JITSymFlags.isWeak() || JITSymFlags.isCommon()) {
+      // First check whether there's already a definition in this instance.
+      // FIXME: Override existing weak definitions with strong ones.
+      if (GlobalSymbolTable.count(Name))
+        continue;
+
+      // Then check whether we found flags for an existing symbol during the
+      // flags lookup earlier.
+      auto FlagsI = SymbolFlags.find(Name);
+      if (FlagsI == SymbolFlags.end() ||
+          (JITSymFlags.isWeak() && !FlagsI->second.isStrong()) ||
+          (JITSymFlags.isCommon() && FlagsI->second.isCommon())) {
+        if (JITSymFlags.isWeak())
+          JITSymFlags &= ~JITSymbolFlags::Weak;
+        if (JITSymFlags.isCommon()) {
+          JITSymFlags &= ~JITSymbolFlags::Common;
+          uint32_t Align = I->getAlignment();
+          uint64_t Size = I->getCommonSize();
+          if (!CommonAlign)
+            CommonAlign = Align;
+          CommonSize += alignTo(CommonSize, Align) + Size;
+          CommonSymbolsToAllocate.push_back(*I);
+        }
+      } else
+        continue;
+    }
+
+    if (Flags & SymbolRef::SF_Absolute &&
+        SymType != object::SymbolRef::ST_File) {
+      uint64_t Addr = 0;
+      if (auto AddrOrErr = I->getAddress())
+        Addr = *AddrOrErr;
       else
-        return SymTypeOrErr.takeError();
+        return AddrOrErr.takeError();
 
-      // Get symbol name.
-      StringRef Name;
-      if (auto NameOrErr = I->getName())
-        Name = *NameOrErr;
+      unsigned SectionID = AbsoluteSymbolSection;
+
+      DEBUG(dbgs() << "\tType: " << SymType << " (absolute) Name: " << Name
+                   << " SID: " << SectionID
+                   << " Offset: " << format("%p", (uintptr_t)Addr)
+                   << " flags: " << Flags << "\n");
+      GlobalSymbolTable[Name] = SymbolTableEntry(SectionID, Addr, JITSymFlags);
+    } else if (SymType == object::SymbolRef::ST_Function ||
+               SymType == object::SymbolRef::ST_Data ||
+               SymType == object::SymbolRef::ST_Unknown ||
+               SymType == object::SymbolRef::ST_Other) {
+
+      section_iterator SI = Obj.section_end();
+      if (auto SIOrErr = I->getSection())
+        SI = *SIOrErr;
       else
-        return NameOrErr.takeError();
+        return SIOrErr.takeError();
 
-      // Compute JIT symbol flags.
-      JITSymbolFlags JITSymFlags = getJITSymbolFlags(*I);
+      if (SI == Obj.section_end())
+        continue;
 
-      // If this is a weak definition, check to see if there's a strong one.
-      // If there is, skip this symbol (we won't be providing it: the strong
-      // definition will). If there's no strong definition, make this definition
-      // strong.
-      if (JITSymFlags.isWeak()) {
-        // First check whether there's already a definition in this instance.
-        // FIXME: Override existing weak definitions with strong ones.
-        if (GlobalSymbolTable.count(Name))
-          continue;
-        // Then check the symbol resolver to see if there's a definition
-        // elsewhere in this logical dylib.
-        if (auto Sym = Resolver.findSymbolInLogicalDylib(Name)) {
-          if (Sym.getFlags().isStrong())
-            continue;
-        } else if (auto Err = Sym.takeError())
-          return std::move(Err);
-        // else
-        JITSymFlags &= ~JITSymbolFlags::Weak;
-      }
+      // Get symbol offset.
+      uint64_t SectOffset;
+      if (auto Err = getOffset(*I, *SI, SectOffset))
+        return std::move(Err);
 
-      if (Flags & SymbolRef::SF_Absolute &&
-          SymType != object::SymbolRef::ST_File) {
-        uint64_t Addr = 0;
-        if (auto AddrOrErr = I->getAddress())
-          Addr = *AddrOrErr;
-        else
-          return AddrOrErr.takeError();
+      bool IsCode = SI->isText();
+      unsigned SectionID;
+      if (auto SectionIDOrErr =
+              findOrEmitSection(Obj, *SI, IsCode, LocalSections))
+        SectionID = *SectionIDOrErr;
+      else
+        return SectionIDOrErr.takeError();
 
-        unsigned SectionID = AbsoluteSymbolSection;
-
-        DEBUG(dbgs() << "\tType: " << SymType << " (absolute) Name: " << Name
-                     << " SID: " << SectionID << " Offset: "
-                     << format("%p", (uintptr_t)Addr)
-                     << " flags: " << Flags << "\n");
-        GlobalSymbolTable[Name] =
-          SymbolTableEntry(SectionID, Addr, JITSymFlags);
-      } else if (SymType == object::SymbolRef::ST_Function ||
-                 SymType == object::SymbolRef::ST_Data ||
-                 SymType == object::SymbolRef::ST_Unknown ||
-                 SymType == object::SymbolRef::ST_Other) {
-
-        section_iterator SI = Obj.section_end();
-        if (auto SIOrErr = I->getSection())
-          SI = *SIOrErr;
-        else
-          return SIOrErr.takeError();
-
-        if (SI == Obj.section_end())
-          continue;
-
-        // Get symbol offset.
-        uint64_t SectOffset;
-        if (auto Err = getOffset(*I, *SI, SectOffset))
-          return std::move(Err);
-
-        bool IsCode = SI->isText();
-        unsigned SectionID;
-        if (auto SectionIDOrErr = findOrEmitSection(Obj, *SI, IsCode,
-                                                    LocalSections))
-          SectionID = *SectionIDOrErr;
-        else
-          return SectionIDOrErr.takeError();
-
-        DEBUG(dbgs() << "\tType: " << SymType << " Name: " << Name
-                     << " SID: " << SectionID << " Offset: "
-                     << format("%p", (uintptr_t)SectOffset)
-                     << " flags: " << Flags << "\n");
-        GlobalSymbolTable[Name] =
+      DEBUG(dbgs() << "\tType: " << SymType << " Name: " << Name
+                   << " SID: " << SectionID
+                   << " Offset: " << format("%p", (uintptr_t)SectOffset)
+                   << " flags: " << Flags << "\n");
+      GlobalSymbolTable[Name] =
           SymbolTableEntry(SectionID, SectOffset, JITSymFlags);
-      }
     }
   }
 
   // Allocate common symbols
-  if (auto Err = emitCommonSymbols(Obj, CommonSymbols))
+  if (auto Err = emitCommonSymbols(Obj, CommonSymbolsToAllocate, CommonSize,
+                                   CommonAlign))
     return std::move(Err);
 
   // Parse and process relocations
@@ -621,45 +653,12 @@ JITSymbolFlags RuntimeDyldImpl::getJITSymbolFlags(const BasicSymbolRef &SR) {
 }
 
 Error RuntimeDyldImpl::emitCommonSymbols(const ObjectFile &Obj,
-                                         CommonSymbolList &CommonSymbols) {
-  if (CommonSymbols.empty())
+                                         CommonSymbolList &SymbolsToAllocate,
+                                         uint64_t CommonSize,
+                                         uint32_t CommonAlign) {
+  if (SymbolsToAllocate.empty())
     return Error::success();
 
-  uint64_t CommonSize = 0;
-  uint32_t CommonAlign = CommonSymbols.begin()->getAlignment();
-  CommonSymbolList SymbolsToAllocate;
-
-  DEBUG(dbgs() << "Processing common symbols...\n");
-
-  for (const auto &Sym : CommonSymbols) {
-    StringRef Name;
-    if (auto NameOrErr = Sym.getName())
-      Name = *NameOrErr;
-    else
-      return NameOrErr.takeError();
-
-    // Skip common symbols already elsewhere.
-    if (GlobalSymbolTable.count(Name)) {
-      DEBUG(dbgs() << "\tSkipping already emitted common symbol '" << Name
-                   << "'\n");
-      continue;
-    }
-
-    if (auto Sym = Resolver.findSymbolInLogicalDylib(Name)) {
-      if (!Sym.getFlags().isCommon()) {
-        DEBUG(dbgs() << "\tSkipping common symbol '" << Name
-                     << "' in favor of stronger definition.\n");
-        continue;
-      }
-    }
-    uint32_t Align = Sym.getAlignment();
-    uint64_t Size = Sym.getCommonSize();
-
-    CommonSize = alignTo(CommonSize, Align) + Size;
-
-    SymbolsToAllocate.push_back(Sym);
-  }
-
   // Allocate memory for the section
   unsigned SectionID = Sections.size();
   uint8_t *Addr = MemMgr.allocateDataSection(CommonSize, CommonAlign, SectionID,
@@ -997,7 +996,40 @@ void RuntimeDyldImpl::resolveRelocationList(const RelocationList &Relocs,
 }
 
 Error RuntimeDyldImpl::resolveExternalSymbols() {
+  JITSymbolResolver::LookupResult ExternalSymbolMap;
+
+  // Resolution can trigger emission of more symbols, so iterate until
+  // we've resolved *everything*.
+  {
+    JITSymbolResolver::SymbolNameSet ResolvedSymbols;
+
+    while (true) {
+      JITSymbolResolver::SymbolNameSet NewSymbols;
+
+      for (auto &RelocKV : ExternalSymbolRelocations) {
+        StringRef Name = RelocKV.first();
+        if (!Name.empty() && !GlobalSymbolTable.count(Name) &&
+            !ResolvedSymbols.count(Name))
+          NewSymbols.insert(Name);
+      }
+
+      if (NewSymbols.empty())
+        break;
+
+      auto NewResolverResults = Resolver.lookup(NewSymbols);
+      if (!NewResolverResults)
+        return NewResolverResults.takeError();
+
+      for (auto &RRKV : *NewResolverResults) {
+        assert(!ResolvedSymbols.count(RRKV.first) && "Redundant resolution?");
+        ExternalSymbolMap.insert(RRKV);
+        ResolvedSymbols.insert(RRKV.first);
+      }
+    }
+  }
+
   while (!ExternalSymbolRelocations.empty()) {
+
     StringMap<RelocationList>::iterator i = ExternalSymbolRelocations.begin();
 
     StringRef Name = i->first();
@@ -1012,29 +1044,10 @@ Error RuntimeDyldImpl::resolveExternalSymbols() {
       JITSymbolFlags Flags;
       RTDyldSymbolTable::const_iterator Loc = GlobalSymbolTable.find(Name);
       if (Loc == GlobalSymbolTable.end()) {
-        // This is an external symbol, try to get its address from the symbol
-        // resolver.
-        // First search for the symbol in this logical dylib.
-        if (auto Sym = Resolver.findSymbolInLogicalDylib(Name.data())) {
-          if (auto AddrOrErr = Sym.getAddress()) {
-            Addr = *AddrOrErr;
-            Flags = Sym.getFlags();
-          } else
-            return AddrOrErr.takeError();
-        } else if (auto Err = Sym.takeError())
-          return Err;
-
-        // If that fails, try searching for an external symbol.
-        if (!Addr) {
-          if (auto Sym = Resolver.findSymbol(Name.data())) {
-            if (auto AddrOrErr = Sym.getAddress()) {
-              Addr = *AddrOrErr;
-              Flags = Sym.getFlags();
-            } else
-              return AddrOrErr.takeError();
-          } else if (auto Err = Sym.takeError())
-            return Err;
-        }
+        auto RRI = ExternalSymbolMap.find(Name);
+        assert(RRI != ExternalSymbolMap.end() && "No result for symbol");
+        Addr = RRI->second.getAddress();
+        Flags = RRI->second.getFlags();
         // The call to getSymbolAddress may have caused additional modules to
         // be loaded, which may have added new entries to the
         // ExternalSymbolRelocations map.  Consquently, we need to update our
@@ -1095,6 +1108,7 @@ uint64_t RuntimeDyld::LoadedObjectInfo::getSectionLoadAddress(
 
 void RuntimeDyld::MemoryManager::anchor() {}
 void JITSymbolResolver::anchor() {}
+void LegacyJITSymbolResolver::anchor() {}
 
 RuntimeDyld::RuntimeDyld(RuntimeDyld::MemoryManager &MemMgr,
                          JITSymbolResolver &Resolver)
diff --git a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldChecker.cpp b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldChecker.cpp
index 5bc7434e703..0f4534f2c9f 100644
--- a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldChecker.cpp
+++ b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldChecker.cpp
@@ -731,7 +731,14 @@ bool RuntimeDyldCheckerImpl::checkAllRulesInBuffer(StringRef RulePrefix,
 bool RuntimeDyldCheckerImpl::isSymbolValid(StringRef Symbol) const {
   if (getRTDyld().getSymbol(Symbol))
     return true;
-  return !!getRTDyld().Resolver.findSymbol(Symbol);
+  JITSymbolResolver::SymbolNameSet Symbols({Symbol});
+  auto Result = getRTDyld().Resolver.lookup(Symbols);
+  if (!Result) {
+    logAllUnhandledErrors(Result.takeError(), errs(), "RTDyldChecker: ");
+    return false;
+  }
+  assert(Result->count(Symbol) && "Missing symbol result");
+  return true;
 }
 
 uint64_t RuntimeDyldCheckerImpl::getSymbolLocalAddr(StringRef Symbol) const {
@@ -742,7 +749,16 @@ uint64_t RuntimeDyldCheckerImpl::getSymbolLocalAddr(StringRef Symbol) const {
 uint64_t RuntimeDyldCheckerImpl::getSymbolRemoteAddr(StringRef Symbol) const {
   if (auto InternalSymbol = getRTDyld().getSymbol(Symbol))
     return InternalSymbol.getAddress();
-  return cantFail(getRTDyld().Resolver.findSymbol(Symbol).getAddress());
+
+  JITSymbolResolver::SymbolNameSet Symbols({Symbol});
+  auto Result = getRTDyld().Resolver.lookup(Symbols);
+  if (!Result) {
+    logAllUnhandledErrors(Result.takeError(), errs(), "RTDyldChecker: ");
+    return 0;
+  }
+  auto I = Result->find(Symbol);
+  assert(I != Result->end() && "Missing symbol result");
+  return I->second.getAddress();
 }
 
 uint64_t RuntimeDyldCheckerImpl::readMemoryAtAddr(uint64_t SrcAddr,
diff --git a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h
index e046a8504e9..e940004bb2e 100644
--- a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h
+++ b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h
@@ -385,7 +385,8 @@ protected:
   /// new section for them and update the symbol mappings in the object and
   /// symbol table.
   Error emitCommonSymbols(const ObjectFile &Obj,
-                          CommonSymbolList &CommonSymbols);
+                          CommonSymbolList &CommonSymbols, uint64_t CommonSize,
+                          uint32_t CommonAlign);
 
   /// \brief Emits section data from the object file to the MemoryManager.
   /// \param IsCode if it's true then allocateCodeSection() will be
diff --git a/tools/lli/RemoteJITUtils.h b/tools/lli/RemoteJITUtils.h
index 4e948413865..944881070c7 100644
--- a/tools/lli/RemoteJITUtils.h
+++ b/tools/lli/RemoteJITUtils.h
@@ -84,7 +84,7 @@ public:
     this->MemMgr = std::move(MemMgr);
   }
 
-  void setResolver(std::shared_ptr<JITSymbolResolver> Resolver) {
+  void setResolver(std::shared_ptr<LegacyJITSymbolResolver> Resolver) {
     this->Resolver = std::move(Resolver);
   }
 
@@ -145,7 +145,7 @@ public:
 
 private:
   std::unique_ptr<RuntimeDyld::MemoryManager> MemMgr;
-  std::shared_ptr<JITSymbolResolver> Resolver;
+  std::shared_ptr<LegacyJITSymbolResolver> Resolver;
 };
 }