[llvm-branch-commits] [llvm] [llvm-exegesis] Switch from MCJIT to LLJIT (PR #72838)

[Clement Courbet via llvm-branch-commits]

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@@ -324,66 +325,44 @@ object::OwningBinary<object::ObjectFile> getObjectFromFile(StringRef Filename) {
   return cantFail(object::ObjectFile::createObjectFile(Filename));
 }
 
-namespace {
-
-// Implementation of this class relies on the fact that a single object with a
-// single function will be loaded into memory.
-class TrackingSectionMemoryManager : public SectionMemoryManager {
-public:
-  explicit TrackingSectionMemoryManager(uintptr_t *CodeSize)
-      : CodeSize(CodeSize) {}
-
-  uint8_t *allocateCodeSection(uintptr_t Size, unsigned Alignment,
-                               unsigned SectionID,
-                               StringRef SectionName) override {
-    *CodeSize = Size;
-    return SectionMemoryManager::allocateCodeSection(Size, Alignment, SectionID,
-                                                     SectionName);
-  }
-
-private:
-  uintptr_t *const CodeSize = nullptr;
-};
-
-} // namespace
-
 Expected<ExecutableFunction> ExecutableFunction::create(
     std::unique_ptr<LLVMTargetMachine> TM,
     object::OwningBinary<object::ObjectFile> &&ObjectFileHolder) {
   assert(ObjectFileHolder.getBinary() && "cannot create object file");
   std::unique_ptr<LLVMContext> Ctx = std::make_unique<LLVMContext>();
-  // Initializing the execution engine.
-  // We need to use the JIT EngineKind to be able to add an object file.
-  LLVMLinkInMCJIT();
-  uintptr_t CodeSize = 0;
-  std::string Error;
-  std::unique_ptr<ExecutionEngine> EE(
-      EngineBuilder(createModule(Ctx, TM->createDataLayout()))
-          .setErrorStr(&Error)
-          .setMCPU(TM->getTargetCPU())
-          .setEngineKind(EngineKind::JIT)
-          .setMCJITMemoryManager(
-              std::make_unique<TrackingSectionMemoryManager>(&CodeSize))
-          .create(TM.release()));
-  if (!EE)
-    return make_error<StringError>(Twine(Error), inconvertibleErrorCode());
-  // Adding the generated object file containing the assembled function.
-  // The ExecutionEngine makes sure the object file is copied into an
-  // executable page.
-  EE->addObjectFile(std::move(ObjectFileHolder));
-  // Fetching function bytes.
-  const uint64_t FunctionAddress = EE->getFunctionAddress(FunctionID);
+
+  auto SymbolSizes = object::computeSymbolSizes(*ObjectFileHolder.getBinary());
+  assert(SymbolSizes.size() == 3);
+  uintptr_t CodeSize = std::get<1>(SymbolSizes[2]);
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legrosbuffle wrote:

Can you add a comment to explain which symbols we're expecting ?

https://github.com/llvm/llvm-project/pull/72838