1 //===- ExecutionEngine.cpp - MLIR Execution engine and utils --------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements the execution engine for MLIR modules based on LLVM Orc
10 // JIT engine.
11 //
12 //===----------------------------------------------------------------------===//
13 #include "mlir/ExecutionEngine/ExecutionEngine.h"
14 #include "mlir/Dialect/LLVMIR/LLVMDialect.h"
15 #include "mlir/IR/Function.h"
16 #include "mlir/IR/Module.h"
17 #include "mlir/Support/FileUtilities.h"
18 #include "mlir/Target/LLVMIR.h"
19 
20 #include "llvm/ExecutionEngine/JITEventListener.h"
21 #include "llvm/ExecutionEngine/ObjectCache.h"
22 #include "llvm/ExecutionEngine/Orc/CompileUtils.h"
23 #include "llvm/ExecutionEngine/Orc/ExecutionUtils.h"
24 #include "llvm/ExecutionEngine/Orc/IRCompileLayer.h"
25 #include "llvm/ExecutionEngine/Orc/IRTransformLayer.h"
26 #include "llvm/ExecutionEngine/Orc/JITTargetMachineBuilder.h"
27 #include "llvm/ExecutionEngine/Orc/RTDyldObjectLinkingLayer.h"
28 #include "llvm/ExecutionEngine/SectionMemoryManager.h"
29 #include "llvm/IR/IRBuilder.h"
30 #include "llvm/Support/Debug.h"
31 #include "llvm/Support/Error.h"
32 #include "llvm/Support/Host.h"
33 #include "llvm/Support/TargetRegistry.h"
34 #include "llvm/Support/ToolOutputFile.h"
35 
36 #define DEBUG_TYPE "execution-engine"
37 
38 using namespace mlir;
39 using llvm::dbgs;
40 using llvm::Error;
41 using llvm::errs;
42 using llvm::Expected;
43 using llvm::LLVMContext;
44 using llvm::MemoryBuffer;
45 using llvm::MemoryBufferRef;
46 using llvm::Module;
47 using llvm::SectionMemoryManager;
48 using llvm::StringError;
49 using llvm::Triple;
50 using llvm::orc::DynamicLibrarySearchGenerator;
51 using llvm::orc::ExecutionSession;
52 using llvm::orc::IRCompileLayer;
53 using llvm::orc::JITTargetMachineBuilder;
54 using llvm::orc::MangleAndInterner;
55 using llvm::orc::RTDyldObjectLinkingLayer;
56 using llvm::orc::SymbolMap;
57 using llvm::orc::ThreadSafeModule;
58 using llvm::orc::TMOwningSimpleCompiler;
59 
60 /// Wrap a string into an llvm::StringError.
61 static Error make_string_error(const Twine &message) {
62   return llvm::make_error<StringError>(message.str(),
63                                        llvm::inconvertibleErrorCode());
64 }
65 
66 void SimpleObjectCache::notifyObjectCompiled(const Module *M,
67                                              MemoryBufferRef ObjBuffer) {
68   cachedObjects[M->getModuleIdentifier()] = MemoryBuffer::getMemBufferCopy(
69       ObjBuffer.getBuffer(), ObjBuffer.getBufferIdentifier());
70 }
71 
72 std::unique_ptr<MemoryBuffer> SimpleObjectCache::getObject(const Module *M) {
73   auto I = cachedObjects.find(M->getModuleIdentifier());
74   if (I == cachedObjects.end()) {
75     LLVM_DEBUG(dbgs() << "No object for " << M->getModuleIdentifier()
76                       << " in cache. Compiling.\n");
77     return nullptr;
78   }
79   LLVM_DEBUG(dbgs() << "Object for " << M->getModuleIdentifier()
80                     << " loaded from cache.\n");
81   return MemoryBuffer::getMemBuffer(I->second->getMemBufferRef());
82 }
83 
84 void SimpleObjectCache::dumpToObjectFile(StringRef outputFilename) {
85   // Set up the output file.
86   std::string errorMessage;
87   auto file = openOutputFile(outputFilename, &errorMessage);
88   if (!file) {
89     llvm::errs() << errorMessage << "\n";
90     return;
91   }
92 
93   // Dump the object generated for a single module to the output file.
94   assert(cachedObjects.size() == 1 && "Expected only one object entry.");
95   auto &cachedObject = cachedObjects.begin()->second;
96   file->os() << cachedObject->getBuffer();
97   file->keep();
98 }
99 
100 void ExecutionEngine::dumpToObjectFile(StringRef filename) {
101   cache->dumpToObjectFile(filename);
102 }
103 
104 void ExecutionEngine::registerSymbols(
105     llvm::function_ref<SymbolMap(MangleAndInterner)> symbolMap) {
106   auto &mainJitDylib = jit->getMainJITDylib();
107   cantFail(mainJitDylib.define(
108       absoluteSymbols(symbolMap(llvm::orc::MangleAndInterner(
109           mainJitDylib.getExecutionSession(), jit->getDataLayout())))));
110 }
111 
112 // Setup LLVM target triple from the current machine.
113 bool ExecutionEngine::setupTargetTriple(Module *llvmModule) {
114   // Setup the machine properties from the current architecture.
115   auto targetTriple = llvm::sys::getDefaultTargetTriple();
116   std::string errorMessage;
117   auto target = llvm::TargetRegistry::lookupTarget(targetTriple, errorMessage);
118   if (!target) {
119     errs() << "NO target: " << errorMessage << "\n";
120     return true;
121   }
122   std::unique_ptr<llvm::TargetMachine> machine(
123       target->createTargetMachine(targetTriple, "generic", "", {}, {}));
124   llvmModule->setDataLayout(machine->createDataLayout());
125   llvmModule->setTargetTriple(targetTriple);
126   return false;
127 }
128 
129 static std::string makePackedFunctionName(StringRef name) {
130   return "_mlir_" + name.str();
131 }
132 
133 // For each function in the LLVM module, define an interface function that wraps
134 // all the arguments of the original function and all its results into an i8**
135 // pointer to provide a unified invocation interface.
136 static void packFunctionArguments(Module *module) {
137   auto &ctx = module->getContext();
138   llvm::IRBuilder<> builder(ctx);
139   DenseSet<llvm::Function *> interfaceFunctions;
140   for (auto &func : module->getFunctionList()) {
141     if (func.isDeclaration()) {
142       continue;
143     }
144     if (interfaceFunctions.count(&func)) {
145       continue;
146     }
147 
148     // Given a function `foo(<...>)`, define the interface function
149     // `mlir_foo(i8**)`.
150     auto newType = llvm::FunctionType::get(
151         builder.getVoidTy(), builder.getInt8PtrTy()->getPointerTo(),
152         /*isVarArg=*/false);
153     auto newName = makePackedFunctionName(func.getName());
154     auto funcCst = module->getOrInsertFunction(newName, newType);
155     llvm::Function *interfaceFunc = cast<llvm::Function>(funcCst.getCallee());
156     interfaceFunctions.insert(interfaceFunc);
157 
158     // Extract the arguments from the type-erased argument list and cast them to
159     // the proper types.
160     auto bb = llvm::BasicBlock::Create(ctx);
161     bb->insertInto(interfaceFunc);
162     builder.SetInsertPoint(bb);
163     llvm::Value *argList = interfaceFunc->arg_begin();
164     SmallVector<llvm::Value *, 8> args;
165     args.reserve(llvm::size(func.args()));
166     for (auto &indexedArg : llvm::enumerate(func.args())) {
167       llvm::Value *argIndex = llvm::Constant::getIntegerValue(
168           builder.getInt64Ty(), APInt(64, indexedArg.index()));
169       llvm::Value *argPtrPtr = builder.CreateGEP(argList, argIndex);
170       llvm::Value *argPtr = builder.CreateLoad(argPtrPtr);
171       argPtr = builder.CreateBitCast(
172           argPtr, indexedArg.value().getType()->getPointerTo());
173       llvm::Value *arg = builder.CreateLoad(argPtr);
174       args.push_back(arg);
175     }
176 
177     // Call the implementation function with the extracted arguments.
178     llvm::Value *result = builder.CreateCall(&func, args);
179 
180     // Assuming the result is one value, potentially of type `void`.
181     if (!result->getType()->isVoidTy()) {
182       llvm::Value *retIndex = llvm::Constant::getIntegerValue(
183           builder.getInt64Ty(), APInt(64, llvm::size(func.args())));
184       llvm::Value *retPtrPtr = builder.CreateGEP(argList, retIndex);
185       llvm::Value *retPtr = builder.CreateLoad(retPtrPtr);
186       retPtr = builder.CreateBitCast(retPtr, result->getType()->getPointerTo());
187       builder.CreateStore(result, retPtr);
188     }
189 
190     // The interface function returns void.
191     builder.CreateRetVoid();
192   }
193 }
194 
195 ExecutionEngine::ExecutionEngine(bool enableObjectCache,
196                                  bool enableGDBNotificationListener,
197                                  bool enablePerfNotificationListener)
198     : cache(enableObjectCache ? new SimpleObjectCache() : nullptr),
199       gdbListener(enableGDBNotificationListener
200                       ? llvm::JITEventListener::createGDBRegistrationListener()
201                       : nullptr),
202       perfListener(enablePerfNotificationListener
203                        ? llvm::JITEventListener::createPerfJITEventListener()
204                        : nullptr) {}
205 
206 Expected<std::unique_ptr<ExecutionEngine>> ExecutionEngine::create(
207     ModuleOp m, llvm::function_ref<Error(llvm::Module *)> transformer,
208     Optional<llvm::CodeGenOpt::Level> jitCodeGenOptLevel,
209     ArrayRef<StringRef> sharedLibPaths, bool enableObjectCache,
210     bool enableGDBNotificationListener, bool enablePerfNotificationListener) {
211   auto engine = std::make_unique<ExecutionEngine>(
212       enableObjectCache, enableGDBNotificationListener,
213       enablePerfNotificationListener);
214 
215   std::unique_ptr<llvm::LLVMContext> ctx(new llvm::LLVMContext);
216   auto llvmModule = translateModuleToLLVMIR(m);
217   if (!llvmModule)
218     return make_string_error("could not convert to LLVM IR");
219   // FIXME: the triple should be passed to the translation or dialect conversion
220   // instead of this.  Currently, the LLVM module created above has no triple
221   // associated with it.
222   setupTargetTriple(llvmModule.get());
223   packFunctionArguments(llvmModule.get());
224 
225   // Clone module in a new LLVMContext since translateModuleToLLVMIR buries
226   // ownership too deeply.
227   // TODO(zinenko): Reevaluate model of ownership of LLVMContext in LLVMDialect.
228   std::unique_ptr<Module> deserModule =
229       LLVM::cloneModuleIntoNewContext(ctx.get(), llvmModule.get());
230   auto dataLayout = deserModule->getDataLayout();
231 
232   // Callback to create the object layer with symbol resolution to current
233   // process and dynamically linked libraries.
234   auto objectLinkingLayerCreator = [&](ExecutionSession &session,
235                                        const Triple &TT) {
236     auto objectLayer = std::make_unique<RTDyldObjectLinkingLayer>(
237         session, []() { return std::make_unique<SectionMemoryManager>(); });
238 
239     // Register JIT event listeners if they are enabled.
240     if (engine->gdbListener)
241       objectLayer->registerJITEventListener(*engine->gdbListener);
242     if (engine->perfListener)
243       objectLayer->registerJITEventListener(*engine->perfListener);
244 
245     // Resolve symbols from shared libraries.
246     for (auto libPath : sharedLibPaths) {
247       auto mb = llvm::MemoryBuffer::getFile(libPath);
248       if (!mb) {
249         errs() << "Fail to create MemoryBuffer for: " << libPath << "\n";
250         continue;
251       }
252       auto &JD = session.createBareJITDylib(std::string(libPath));
253       auto loaded = DynamicLibrarySearchGenerator::Load(
254           libPath.data(), dataLayout.getGlobalPrefix());
255       if (!loaded) {
256         errs() << "Could not load " << libPath << ":\n  " << loaded.takeError()
257                << "\n";
258         continue;
259       }
260       JD.addGenerator(std::move(*loaded));
261       cantFail(objectLayer->add(JD, std::move(mb.get())));
262     }
263 
264     return objectLayer;
265   };
266 
267   // Callback to inspect the cache and recompile on demand. This follows Lang's
268   // LLJITWithObjectCache example.
269   auto compileFunctionCreator = [&](JITTargetMachineBuilder JTMB)
270       -> Expected<std::unique_ptr<IRCompileLayer::IRCompiler>> {
271     if (jitCodeGenOptLevel)
272       JTMB.setCodeGenOptLevel(jitCodeGenOptLevel.getValue());
273     auto TM = JTMB.createTargetMachine();
274     if (!TM)
275       return TM.takeError();
276     return std::make_unique<TMOwningSimpleCompiler>(std::move(*TM),
277                                                     engine->cache.get());
278   };
279 
280   // Create the LLJIT by calling the LLJITBuilder with 2 callbacks.
281   auto jit =
282       cantFail(llvm::orc::LLJITBuilder()
283                    .setCompileFunctionCreator(compileFunctionCreator)
284                    .setObjectLinkingLayerCreator(objectLinkingLayerCreator)
285                    .create());
286 
287   // Add a ThreadSafemodule to the engine and return.
288   ThreadSafeModule tsm(std::move(deserModule), std::move(ctx));
289   if (transformer)
290     cantFail(tsm.withModuleDo(
291         [&](llvm::Module &module) { return transformer(&module); }));
292   cantFail(jit->addIRModule(std::move(tsm)));
293   engine->jit = std::move(jit);
294 
295   // Resolve symbols that are statically linked in the current process.
296   llvm::orc::JITDylib &mainJD = engine->jit->getMainJITDylib();
297   mainJD.addGenerator(
298       cantFail(DynamicLibrarySearchGenerator::GetForCurrentProcess(
299           dataLayout.getGlobalPrefix())));
300 
301   return std::move(engine);
302 }
303 
304 Expected<void (*)(void **)> ExecutionEngine::lookup(StringRef name) const {
305   auto expectedSymbol = jit->lookup(makePackedFunctionName(name));
306 
307   // JIT lookup may return an Error referring to strings stored internally by
308   // the JIT. If the Error outlives the ExecutionEngine, it would want have a
309   // dangling reference, which is currently caught by an assertion inside JIT
310   // thanks to hand-rolled reference counting. Rewrap the error message into a
311   // string before returning. Alternatively, ORC JIT should consider copying
312   // the string into the error message.
313   if (!expectedSymbol) {
314     std::string errorMessage;
315     llvm::raw_string_ostream os(errorMessage);
316     llvm::handleAllErrors(expectedSymbol.takeError(),
317                           [&os](llvm::ErrorInfoBase &ei) { ei.log(os); });
318     return make_string_error(os.str());
319   }
320 
321   auto rawFPtr = expectedSymbol->getAddress();
322   auto fptr = reinterpret_cast<void (*)(void **)>(rawFPtr);
323   if (!fptr)
324     return make_string_error("looked up function is null");
325   return fptr;
326 }
327 
328 Error ExecutionEngine::invoke(StringRef name, MutableArrayRef<void *> args) {
329   auto expectedFPtr = lookup(name);
330   if (!expectedFPtr)
331     return expectedFPtr.takeError();
332   auto fptr = *expectedFPtr;
333 
334   (*fptr)(args.data());
335 
336   return Error::success();
337 }
338