Ensuring unique names for JITDylib's

[pree-jackie]

Summary

Asserting the multiple JITDylib's with same name are not added to the Execution Session. Adding a method to get pointers to JITDylibs in ExecutionSession.
Fixes PR41937

[pree-jackie]

Wrapping the getJITDylibByName by runSessionLocked Interface to make thread safe creation of JITDylibs

[pree-jackie]

I have squashed two commits into one. Whether I have to send the squashed diff?

[lhames]

Yeah -- this seems to be missing the header side of the patch. You should be able to use the "update diff" option to create a new diff (still attached to this revision) with both sides of the change.

[pree-jackie]

Updated Diff file

[lhames]

Looks good to me.

[lhames]

Oh -- I missed that this was passing the name as a std::string by value. This will result in unnecessary string copies. In general for a case like this you would use an llvm::StringRef -- It's a lightweight string reference type. I'll switch to that before committing.

[pree-jackie]

Thanks :)
Then we can change parameter type of createJITDylib to StringRef instead of std::string.

llvm/trunk/include/llvm/ExecutionEngine/Orc/Core.h

template <typename Func> auto runSessionLocked(Func &&F) -> decltype(F()) {
     std::lock_guard<std::recursive_mutex> Lock(SessionMutex);
     return F();
   }
 
   /// Get the "main" JITDylib, which is created automatically on construction of
   /// the ExecutionSession.
   JITDylib &getMainJITDylib();
 
+  /// Return a pointer to the "name" JITDylib.
+  /// Ownership of JITDylib remains within Execution Session
+  JITDylib *getJITDylibByName(StringRef Name);
+
   /// Add a new JITDylib to this ExecutionSession.
   JITDylib &createJITDylib(std::string Name,
                            bool AddToMainDylibSearchOrder = true);
 
   /// Allocate a module key for a new module to add to the JIT.
   VModuleKey allocateVModule() {
     return runSessionLocked([this]() { return ++LastKey; });
   }

llvm/trunk/lib/ExecutionEngine/Orc/Core.cpp

ExecutionSession::ExecutionSession(std::shared_ptr<SymbolStringPool> SSP)
   // Construct the main dylib.
   JDs.push_back(std::unique_ptr<JITDylib>(new JITDylib(*this, "<main>")));
 }
 
 JITDylib &ExecutionSession::getMainJITDylib() {
   return runSessionLocked([this]() -> JITDylib & { return *JDs.front(); });
 }
 
+JITDylib *ExecutionSession::getJITDylibByName(StringRef Name) {
+  return runSessionLocked([&, this]() -> JITDylib * {
+    for (auto &JD : JDs)
+      if (JD->getName() == Name)
+        return JD.get();
+    return nullptr;
+  });
+}
+
 JITDylib &ExecutionSession::createJITDylib(std::string Name,
                                            bool AddToMainDylibSearchOrder) {
+  assert(!getJITDylibByName(Name) && "JITDylib with that name already exists");
   return runSessionLocked([&, this]() -> JITDylib & {
     JDs.push_back(
         std::unique_ptr<JITDylib>(new JITDylib(*this, std::move(Name))));
     if (AddToMainDylibSearchOrder)
       JDs.front()->addToSearchOrder(*JDs.back());
     return *JDs.back();
   });
 }