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/BuiltinOps.h"
16 #include "mlir/Support/FileUtilities.h"
17 #include "mlir/Target/LLVMIR/Export.h"
18 
19 #include "llvm/ExecutionEngine/JITEventListener.h"
20 #include "llvm/ExecutionEngine/ObjectCache.h"
21 #include "llvm/ExecutionEngine/Orc/CompileUtils.h"
22 #include "llvm/ExecutionEngine/Orc/ExecutionUtils.h"
23 #include "llvm/ExecutionEngine/Orc/IRCompileLayer.h"
24 #include "llvm/ExecutionEngine/Orc/IRTransformLayer.h"
25 #include "llvm/ExecutionEngine/Orc/JITTargetMachineBuilder.h"
26 #include "llvm/ExecutionEngine/Orc/RTDyldObjectLinkingLayer.h"
27 #include "llvm/ExecutionEngine/SectionMemoryManager.h"
28 #include "llvm/IR/IRBuilder.h"
29 #include "llvm/MC/SubtargetFeature.h"
30 #include "llvm/MC/TargetRegistry.h"
31 #include "llvm/Support/Debug.h"
32 #include "llvm/Support/Error.h"
33 #include "llvm/Support/Host.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 
123   std::string cpu(llvm::sys::getHostCPUName());
124   llvm::SubtargetFeatures features;
125   llvm::StringMap<bool> hostFeatures;
126 
127   if (llvm::sys::getHostCPUFeatures(hostFeatures))
128     for (auto &f : hostFeatures)
129       features.AddFeature(f.first(), f.second);
130 
131   std::unique_ptr<llvm::TargetMachine> machine(target->createTargetMachine(
132       targetTriple, cpu, features.getString(), {}, {}));
133   if (!machine) {
134     errs() << "Unable to create target machine\n";
135     return true;
136   }
137   llvmModule->setDataLayout(machine->createDataLayout());
138   llvmModule->setTargetTriple(targetTriple);
139   return false;
140 }
141 
142 static std::string makePackedFunctionName(StringRef name) {
143   return "_mlir_" + name.str();
144 }
145 
146 // For each function in the LLVM module, define an interface function that wraps
147 // all the arguments of the original function and all its results into an i8**
148 // pointer to provide a unified invocation interface.
149 static void packFunctionArguments(Module *module) {
150   auto &ctx = module->getContext();
151   llvm::IRBuilder<> builder(ctx);
152   DenseSet<llvm::Function *> interfaceFunctions;
153   for (auto &func : module->getFunctionList()) {
154     if (func.isDeclaration()) {
155       continue;
156     }
157     if (interfaceFunctions.count(&func)) {
158       continue;
159     }
160 
161     // Given a function `foo(<...>)`, define the interface function
162     // `mlir_foo(i8**)`.
163     auto newType = llvm::FunctionType::get(
164         builder.getVoidTy(), builder.getInt8PtrTy()->getPointerTo(),
165         /*isVarArg=*/false);
166     auto newName = makePackedFunctionName(func.getName());
167     auto funcCst = module->getOrInsertFunction(newName, newType);
168     llvm::Function *interfaceFunc = cast<llvm::Function>(funcCst.getCallee());
169     interfaceFunctions.insert(interfaceFunc);
170 
171     // Extract the arguments from the type-erased argument list and cast them to
172     // the proper types.
173     auto bb = llvm::BasicBlock::Create(ctx);
174     bb->insertInto(interfaceFunc);
175     builder.SetInsertPoint(bb);
176     llvm::Value *argList = interfaceFunc->arg_begin();
177     SmallVector<llvm::Value *, 8> args;
178     args.reserve(llvm::size(func.args()));
179     for (auto &indexedArg : llvm::enumerate(func.args())) {
180       llvm::Value *argIndex = llvm::Constant::getIntegerValue(
181           builder.getInt64Ty(), APInt(64, indexedArg.index()));
182       llvm::Value *argPtrPtr = builder.CreateGEP(
183           builder.getInt8PtrTy(), argList, argIndex);
184       llvm::Value *argPtr = builder.CreateLoad(builder.getInt8PtrTy(),
185                                                argPtrPtr);
186       llvm::Type *argTy = indexedArg.value().getType();
187       argPtr = builder.CreateBitCast(argPtr, argTy->getPointerTo());
188       llvm::Value *arg = builder.CreateLoad(argTy, argPtr);
189       args.push_back(arg);
190     }
191 
192     // Call the implementation function with the extracted arguments.
193     llvm::Value *result = builder.CreateCall(&func, args);
194 
195     // Assuming the result is one value, potentially of type `void`.
196     if (!result->getType()->isVoidTy()) {
197       llvm::Value *retIndex = llvm::Constant::getIntegerValue(
198           builder.getInt64Ty(), APInt(64, llvm::size(func.args())));
199       llvm::Value *retPtrPtr =
200           builder.CreateGEP(builder.getInt8PtrTy(), argList, retIndex);
201       llvm::Value *retPtr = builder.CreateLoad(builder.getInt8PtrTy(),
202                                                retPtrPtr);
203       retPtr = builder.CreateBitCast(retPtr, result->getType()->getPointerTo());
204       builder.CreateStore(result, retPtr);
205     }
206 
207     // The interface function returns void.
208     builder.CreateRetVoid();
209   }
210 }
211 
212 ExecutionEngine::ExecutionEngine(bool enableObjectCache,
213                                  bool enableGDBNotificationListener,
214                                  bool enablePerfNotificationListener)
215     : cache(enableObjectCache ? new SimpleObjectCache() : nullptr),
216       gdbListener(enableGDBNotificationListener
217                       ? llvm::JITEventListener::createGDBRegistrationListener()
218                       : nullptr),
219       perfListener(enablePerfNotificationListener
220                        ? llvm::JITEventListener::createPerfJITEventListener()
221                        : nullptr) {}
222 
223 Expected<std::unique_ptr<ExecutionEngine>> ExecutionEngine::create(
224     ModuleOp m,
225     llvm::function_ref<std::unique_ptr<llvm::Module>(ModuleOp,
226                                                      llvm::LLVMContext &)>
227         llvmModuleBuilder,
228     llvm::function_ref<Error(llvm::Module *)> transformer,
229     Optional<llvm::CodeGenOpt::Level> jitCodeGenOptLevel,
230     ArrayRef<StringRef> sharedLibPaths, bool enableObjectCache,
231     bool enableGDBNotificationListener, bool enablePerfNotificationListener) {
232   auto engine = std::make_unique<ExecutionEngine>(
233       enableObjectCache, enableGDBNotificationListener,
234       enablePerfNotificationListener);
235 
236   std::unique_ptr<llvm::LLVMContext> ctx(new llvm::LLVMContext);
237   auto llvmModule = llvmModuleBuilder ? llvmModuleBuilder(m, *ctx)
238                                       : translateModuleToLLVMIR(m, *ctx);
239   if (!llvmModule)
240     return make_string_error("could not convert to LLVM IR");
241   // FIXME: the triple should be passed to the translation or dialect conversion
242   // instead of this.  Currently, the LLVM module created above has no triple
243   // associated with it.
244   setupTargetTriple(llvmModule.get());
245   packFunctionArguments(llvmModule.get());
246 
247   auto dataLayout = llvmModule->getDataLayout();
248 
249   // Callback to create the object layer with symbol resolution to current
250   // process and dynamically linked libraries.
251   auto objectLinkingLayerCreator = [&](ExecutionSession &session,
252                                        const Triple &TT) {
253     auto objectLayer = std::make_unique<RTDyldObjectLinkingLayer>(
254         session, []() { return std::make_unique<SectionMemoryManager>(); });
255 
256     // Register JIT event listeners if they are enabled.
257     if (engine->gdbListener)
258       objectLayer->registerJITEventListener(*engine->gdbListener);
259     if (engine->perfListener)
260       objectLayer->registerJITEventListener(*engine->perfListener);
261 
262     // COFF format binaries (Windows) need special handling to deal with
263     // exported symbol visibility.
264     // cf llvm/lib/ExecutionEngine/Orc/LLJIT.cpp LLJIT::createObjectLinkingLayer
265     llvm::Triple targetTriple(llvm::Twine(llvmModule->getTargetTriple()));
266     if (targetTriple.isOSBinFormatCOFF()) {
267       objectLayer->setOverrideObjectFlagsWithResponsibilityFlags(true);
268       objectLayer->setAutoClaimResponsibilityForObjectSymbols(true);
269     }
270 
271     // Resolve symbols from shared libraries.
272     for (auto libPath : sharedLibPaths) {
273       auto mb = llvm::MemoryBuffer::getFile(libPath);
274       if (!mb) {
275         errs() << "Failed to create MemoryBuffer for: " << libPath
276                << "\nError: " << mb.getError().message() << "\n";
277         continue;
278       }
279       auto &JD = session.createBareJITDylib(std::string(libPath));
280       auto loaded = DynamicLibrarySearchGenerator::Load(
281           libPath.data(), dataLayout.getGlobalPrefix());
282       if (!loaded) {
283         errs() << "Could not load " << libPath << ":\n  " << loaded.takeError()
284                << "\n";
285         continue;
286       }
287       JD.addGenerator(std::move(*loaded));
288       cantFail(objectLayer->add(JD, std::move(mb.get())));
289     }
290 
291     return objectLayer;
292   };
293 
294   // Callback to inspect the cache and recompile on demand. This follows Lang's
295   // LLJITWithObjectCache example.
296   auto compileFunctionCreator = [&](JITTargetMachineBuilder JTMB)
297       -> Expected<std::unique_ptr<IRCompileLayer::IRCompiler>> {
298     if (jitCodeGenOptLevel)
299       JTMB.setCodeGenOptLevel(jitCodeGenOptLevel.getValue());
300     auto TM = JTMB.createTargetMachine();
301     if (!TM)
302       return TM.takeError();
303     return std::make_unique<TMOwningSimpleCompiler>(std::move(*TM),
304                                                     engine->cache.get());
305   };
306 
307   // Create the LLJIT by calling the LLJITBuilder with 2 callbacks.
308   auto jit =
309       cantFail(llvm::orc::LLJITBuilder()
310                    .setCompileFunctionCreator(compileFunctionCreator)
311                    .setObjectLinkingLayerCreator(objectLinkingLayerCreator)
312                    .create());
313 
314   // Add a ThreadSafemodule to the engine and return.
315   ThreadSafeModule tsm(std::move(llvmModule), std::move(ctx));
316   if (transformer)
317     cantFail(tsm.withModuleDo(
318         [&](llvm::Module &module) { return transformer(&module); }));
319   cantFail(jit->addIRModule(std::move(tsm)));
320   engine->jit = std::move(jit);
321 
322   // Resolve symbols that are statically linked in the current process.
323   llvm::orc::JITDylib &mainJD = engine->jit->getMainJITDylib();
324   mainJD.addGenerator(
325       cantFail(DynamicLibrarySearchGenerator::GetForCurrentProcess(
326           dataLayout.getGlobalPrefix())));
327 
328   return std::move(engine);
329 }
330 
331 Expected<void (*)(void **)> ExecutionEngine::lookup(StringRef name) const {
332   auto expectedSymbol = jit->lookup(makePackedFunctionName(name));
333 
334   // JIT lookup may return an Error referring to strings stored internally by
335   // the JIT. If the Error outlives the ExecutionEngine, it would want have a
336   // dangling reference, which is currently caught by an assertion inside JIT
337   // thanks to hand-rolled reference counting. Rewrap the error message into a
338   // string before returning. Alternatively, ORC JIT should consider copying
339   // the string into the error message.
340   if (!expectedSymbol) {
341     std::string errorMessage;
342     llvm::raw_string_ostream os(errorMessage);
343     llvm::handleAllErrors(expectedSymbol.takeError(),
344                           [&os](llvm::ErrorInfoBase &ei) { ei.log(os); });
345     return make_string_error(os.str());
346   }
347 
348   auto rawFPtr = expectedSymbol->getAddress();
349   auto fptr = reinterpret_cast<void (*)(void **)>(rawFPtr);
350   if (!fptr)
351     return make_string_error("looked up function is null");
352   return fptr;
353 }
354 
355 Error ExecutionEngine::invokePacked(StringRef name,
356                                     MutableArrayRef<void *> args) {
357   auto expectedFPtr = lookup(name);
358   if (!expectedFPtr)
359     return expectedFPtr.takeError();
360   auto fptr = *expectedFPtr;
361 
362   (*fptr)(args.data());
363 
364   return Error::success();
365 }
366