[ORC] Make ObjectLinkingLayer own its jitlink::MemoryManager.

This relieves ObjectLinkingLayer clients of the responsibility of holding the
memory manager. This makes it easier to select between RTDyldObjectLinkingLayer
(which already owned its memory manager factory) and ObjectLinkingLayer at
runtime as clients aren't required to hold a jitlink::MemoryManager field just
in case ObjectLinkingLayer is selected.

llvm/include/llvm/ExecutionEngine/Orc/ObjectLinkingLayer.h

@@ -79,7 +79,7 @@ public:
   /// Construct an ObjectLinkingLayer with the given NotifyLoaded,
   /// and NotifyEmitted functors.
   ObjectLinkingLayer(ExecutionSession &ES,
-                     jitlink::JITLinkMemoryManager &MemMgr);
+                     std::unique_ptr<jitlink::JITLinkMemoryManager> MemMgr);
 
   /// Destruct an ObjectLinkingLayer.
   ~ObjectLinkingLayer();
@@ -145,7 +145,7 @@ private:
   Error removeAllModules();
 
   mutable std::mutex LayerMutex;
-  jitlink::JITLinkMemoryManager &MemMgr;
+  std::unique_ptr<jitlink::JITLinkMemoryManager> MemMgr;
   bool OverrideObjectFlags = false;
   bool AutoClaimObjectSymbols = false;
   ReturnObjectBufferFunction ReturnObjectBuffer;

llvm/lib/ExecutionEngine/Orc/ObjectLinkingLayer.cpp

@@ -36,7 +36,7 @@ public:
       Layer.ReturnObjectBuffer(std::move(ObjBuffer));
   }
 
-  JITLinkMemoryManager &getMemoryManager() override { return Layer.MemMgr; }
+  JITLinkMemoryManager &getMemoryManager() override { return *Layer.MemMgr; }
 
   MemoryBufferRef getObjectBuffer() const override {
     return ObjBuffer->getMemBufferRef();
@@ -328,9 +328,9 @@ private:
 
 ObjectLinkingLayer::Plugin::~Plugin() {}
 
-ObjectLinkingLayer::ObjectLinkingLayer(ExecutionSession &ES,
-                                       JITLinkMemoryManager &MemMgr)
-    : ObjectLayer(ES), MemMgr(MemMgr) {}
+ObjectLinkingLayer::ObjectLinkingLayer(
+    ExecutionSession &ES, std::unique_ptr<JITLinkMemoryManager> MemMgr)
+    : ObjectLayer(ES), MemMgr(std::move(MemMgr)) {}
 
 ObjectLinkingLayer::~ObjectLinkingLayer() {
   if (auto Err = removeAllModules())

llvm/tools/llvm-jitlink/llvm-jitlink.cpp

@@ -397,8 +397,8 @@ static std::unique_ptr<jitlink::JITLinkMemoryManager> createMemoryManager() {
 }
 
 Session::Session(Triple TT)
-    : MainJD(ES.createJITDylib("<main>")), MemMgr(createMemoryManager()),
-      ObjLayer(ES, *MemMgr), TT(std::move(TT)) {
+    : MainJD(ES.createJITDylib("<main>")), ObjLayer(ES, createMemoryManager()),
+      TT(std::move(TT)) {
 
   /// Local ObjectLinkingLayer::Plugin class to forward modifyPassConfig to the
   /// Session.

llvm/tools/llvm-jitlink/llvm-jitlink.h

@@ -27,7 +27,6 @@ namespace llvm {
 struct Session {
   orc::ExecutionSession ES;
   orc::JITDylib &MainJD;
-  std::unique_ptr<jitlink::JITLinkMemoryManager> MemMgr;
   orc::ObjectLinkingLayer ObjLayer;
   std::vector<orc::JITDylib *> JDSearchOrder;
   Triple TT;