Add a HowToUseLLJIT example project.

A very minimal demo of how to use the LLJIT class, along the lines of the old
HowToUseJIT example.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@361435 91177308-0d34-0410-b5e6-96231b3b80d8

examples/CMakeLists.txt

@@ -1,6 +1,7 @@
 add_subdirectory(BrainF)
 add_subdirectory(Fibonacci)
 add_subdirectory(HowToUseJIT)
+add_subdirectory(HowToUseLLJIT)
 add_subdirectory(Kaleidoscope)
 add_subdirectory(ModuleMaker)
 

examples/HowToUseLLJIT/CMakeLists.txt

@@ -0,0 +1,10 @@
+set(LLVM_LINK_COMPONENTS
+  Core
+  OrcJIT
+  Support
+  nativecodegen
+  )
+
+add_llvm_example(HowToUseLLJIT
+  HowToUseLLJIT.cpp
+  )

examples/HowToUseLLJIT/HowToUseLLJIT.cpp

@@ -0,0 +1,74 @@
+#include "llvm/ExecutionEngine/Orc/LLJIT.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Support/InitLLVM.h"
+#include "llvm/Support/TargetSelect.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace llvm;
+using namespace llvm::orc;
+
+ExitOnError ExitOnErr;
+
+ThreadSafeModule createDemoModule() {
+  auto Context = llvm::make_unique<LLVMContext>();
+  auto M = make_unique<Module>("test", *Context);
+
+  // Create the add1 function entry and insert this entry into module M.  The
+  // function will have a return type of "int" and take an argument of "int".
+  Function *Add1F =
+      Function::Create(FunctionType::get(Type::getInt32Ty(*Context),
+                                         {Type::getInt32Ty(*Context)}, false),
+                       Function::ExternalLinkage, "add1", M.get());
+
+  // Add a basic block to the function. As before, it automatically inserts
+  // because of the last argument.
+  BasicBlock *BB = BasicBlock::Create(*Context, "EntryBlock", Add1F);
+
+  // Create a basic block builder with default parameters.  The builder will
+  // automatically append instructions to the basic block `BB'.
+  IRBuilder<> builder(BB);
+
+  // Get pointers to the constant `1'.
+  Value *One = builder.getInt32(1);
+
+  // Get pointers to the integer argument of the add1 function...
+  assert(Add1F->arg_begin() != Add1F->arg_end()); // Make sure there's an arg
+  Argument *ArgX = &*Add1F->arg_begin();          // Get the arg
+  ArgX->setName("AnArg"); // Give it a nice symbolic name for fun.
+
+  // Create the add instruction, inserting it into the end of BB.
+  Value *Add = builder.CreateAdd(One, ArgX);
+
+  // Create the return instruction and add it to the basic block
+  builder.CreateRet(Add);
+
+  return ThreadSafeModule(std::move(M), std::move(Context));
+}
+
+int main(int argc, char *argv[]) {
+  // Initialize LLVM.
+  InitLLVM X(argc, argv);
+
+  InitializeNativeTarget();
+  InitializeNativeTargetAsmPrinter();
+
+  cl::ParseCommandLineOptions(argc, argv, "HowToUseLLJIT");
+  ExitOnErr.setBanner(std::string(argv[0]) + ": ");
+
+  // Create an LLJIT instance.
+  auto J = ExitOnErr(LLJITBuilder().create());
+  auto M = createDemoModule();
+
+  ExitOnErr(J->addIRModule(std::move(M)));
+
+  // Look up the JIT'd function, cast it to a function pointer, then call it.
+  auto Add1Sym = ExitOnErr(J->lookup("add1"));
+  int (*Add1)(int) = (int (*)(int))Add1Sym.getAddress();
+
+  int Result = Add1(42);
+  outs() << "add1(42) = " << Result << "\n";
+
+  return 0;
+}