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//===------- HowToUseLLJIT.cpp - An example use of ORC-based LLJIT --------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// This small program provides an example of how to quickly build a small
// module with a 'add1' function and use of IRBuilder to create add & return
// instructions.
// Goal:
// The goal of this snippet is to create in the memory
// the LLVM module consisting of a function as follow:
// int add1(int x) {
// return x+1;
// }
// add1(42);
// then compile the module via LLJIT, then execute the 'add1'
// function and return result to a driver, i.e. to a "host program".
#include "llvm/ExecutionEngine/Orc/LLJIT.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/CommandLine.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 = std::make_unique<LLVMContext>();
auto M = std::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 =
{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
return ThreadSafeModule(std::move(M), std::move(Context));
int main(int argc, char *argv[]) {
// Initialize LLVM.
InitLLVM X(argc, argv);
cl::ParseCommandLineOptions(argc, argv, "HowToUseLLJIT");
ExitOnErr.setBanner(std::string(argv[0]) + ": ");
// Create an LLJIT instance.
auto J = ExitOnErr(LLJITBuilder().create());
auto M = createDemoModule();
// Look up the JIT'd function, cast it to a function pointer, then call it.
auto Add1Addr = ExitOnErr(J->lookup("add1"));
int (*Add1)(int) = Add1Addr.toPtr<int(int)>();
int Result = Add1(42);
outs() << "add1(42) = " << Result << "\n";
return 0;