Fix LLVM memory manager for LLVM 6.0 and higher

Refactor code to avoid unecessary casts

Author: fpsunflower

src/include/OSL/llvm_util.h

@@ -43,7 +43,7 @@ namespace llvm {
   class ExecutionEngine;
   class Function;
   class FunctionType;
-  class JITMemoryManager;
+  class SectionMemoryManager;
   class Linker;
   class LLVMContext;
   class Module;
@@ -503,7 +503,7 @@ class OSLEXECPUBLIC LLVM_Util {
     llvm::LLVMContext *m_llvm_context;
     llvm::Module *m_llvm_module;
     IRBuilder *m_builder;
-    MemoryManager *m_llvm_jitmm;
+    llvm::SectionMemoryManager *m_llvm_jitmm;
     llvm::Function *m_current_function;
     llvm::legacy::PassManager *m_llvm_module_passes;
     llvm::legacy::FunctionPassManager *m_llvm_func_passes;

src/liboslexec/llvm_util.cpp

@@ -89,6 +89,32 @@ typedef llvm::SectionMemoryManager LLVMMemoryManager;
 
 
 namespace {
+
+#if OSL_LLVM_VERSION >= 60
+// NOTE: This is a COPY of something internal to LLVM, but since we destroy our LLVMMemoryManager
+//       via global variables we can't rely on the LLVM copy sticking around.
+//       Because of this, the variable must be declared _before_ jitmm_hold so that the object stays
+//       valid until after we have destroyed all our memory managers.
+struct DefaultMMapper final : public llvm::SectionMemoryManager::MemoryMapper {
+    llvm::sys::MemoryBlock
+    allocateMappedMemory(llvm::SectionMemoryManager::AllocationPurpose Purpose,
+                         size_t NumBytes, const llvm::sys::MemoryBlock *const NearBlock,
+                         unsigned Flags, std::error_code &EC) override {
+        return llvm::sys::Memory::allocateMappedMemory(NumBytes, NearBlock, Flags, EC);
+    }
+
+    std::error_code protectMappedMemory(const llvm::sys::MemoryBlock &Block,
+                                        unsigned Flags) override {
+        return llvm::sys::Memory::protectMappedMemory(Block, Flags);
+    }
+
+    std::error_code releaseMappedMemory(llvm::sys::MemoryBlock &M) override {
+        return llvm::sys::Memory::releaseMappedMemory(M);
+    }
+};
+static DefaultMMapper llvm_default_mapper;
+#endif
+
 static OIIO::spin_mutex llvm_global_mutex;
 static bool setup_done = false;
 static boost::thread_specific_ptr<LLVM_Util::PerThreadInfo> perthread_infos;
@@ -185,14 +211,16 @@ class LLVM_Util::MemoryManager : public LLVMMemoryManager {
     virtual void registerEHFrames(uint8_t *Addr, uint64_t LoadAddr, size_t Size) {
         mm->registerEHFrames (Addr, LoadAddr, Size);
     }
-    virtual void deregisterEHFrames(uint8_t *Addr, uint64_t LoadAddr, size_t Size) {
 #if OSL_LLVM_VERSION < 50
+    virtual void deregisterEHFrames(uint8_t *Addr, uint64_t LoadAddr, size_t Size) {
         mm->deregisterEHFrames(Addr, LoadAddr, Size);
+    }
 #else
-        // TODO: verify this is correct
+    virtual void deregisterEHFrames() {
         mm->deregisterEHFrames();
-#endif
     }
+#endif
+
     virtual uint64_t getSymbolAddress(const std::string &Name) {
         return mm->getSymbolAddress (Name);
     }
@@ -231,12 +259,16 @@ LLVM_Util::LLVM_Util (int debuglevel)
             m_thread->llvm_context = new llvm::LLVMContext();
 
         if (! m_thread->llvm_jitmm) {
-            m_thread->llvm_jitmm = new LLVMMemoryManager;
+#if OSL_LLVM_VERSION >= 60
+            m_thread->llvm_jitmm = new LLVMMemoryManager(&llvm_default_mapper);
+#else
+            m_thread->llvm_jitmm = new LLVMMemoryManager();
+#endif
             ASSERT (m_thread->llvm_jitmm);
-            jitmm_hold.push_back (std::shared_ptr<LLVMMemoryManager>(m_thread->llvm_jitmm));
+            jitmm_hold.emplace_back (m_thread->llvm_jitmm);
         }
         // Hold the REAL manager and use it as an argument later
-        m_llvm_jitmm = reinterpret_cast<MemoryManager*>(m_thread->llvm_jitmm);
+        m_llvm_jitmm = m_thread->llvm_jitmm;
     }
 
     m_llvm_context = m_thread->llvm_context;
@@ -442,7 +474,7 @@ LLVM_Util::make_jit_execengine (std::string *err)
 
     // We are actually holding a LLVMMemoryManager
     engine_builder.setMCJITMemoryManager (std::unique_ptr<llvm::RTDyldMemoryManager>
-        (new MemoryManager(reinterpret_cast<LLVMMemoryManager*>(m_llvm_jitmm))));
+        (new MemoryManager(m_llvm_jitmm)));
 
     engine_builder.setOptLevel (llvm::CodeGenOpt::Default);