102 lines · cpp
1//===------- HowToUseLLJIT.cpp - An example use of ORC-based LLJIT --------===//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-exception6//7//===----------------------------------------------------------------------===//8//9// This small program provides an example of how to quickly build a small10// module with a 'add1' function and use of IRBuilder to create add & return11// instructions.12//13// Goal:14// The goal of this snippet is to create in the memory15// the LLVM module consisting of a function as follow:16//17// int add1(int x) {18// return x+1;19// }20// add1(42);21//22// then compile the module via LLJIT, then execute the 'add1'23// function and return result to a driver, i.e. to a "host program".24//25//===----------------------------------------------------------------------===//26 27#include "llvm/ExecutionEngine/Orc/LLJIT.h"28#include "llvm/IR/Function.h"29#include "llvm/IR/IRBuilder.h"30#include "llvm/IR/Module.h"31#include "llvm/Support/CommandLine.h"32#include "llvm/Support/InitLLVM.h"33#include "llvm/Support/TargetSelect.h"34#include "llvm/Support/raw_ostream.h"35 36using namespace llvm;37using namespace llvm::orc;38 39ExitOnError ExitOnErr;40 41ThreadSafeModule createDemoModule() {42 auto Context = std::make_unique<LLVMContext>();43 auto M = std::make_unique<Module>("test", *Context);44 45 // Create the add1 function entry and insert this entry into module M. The46 // function will have a return type of "int" and take an argument of "int".47 Function *Add1F =48 Function::Create(FunctionType::get(Type::getInt32Ty(*Context),49 {Type::getInt32Ty(*Context)}, false),50 Function::ExternalLinkage, "add1", M.get());51 52 // Add a basic block to the function. As before, it automatically inserts53 // because of the last argument.54 BasicBlock *BB = BasicBlock::Create(*Context, "EntryBlock", Add1F);55 56 // Create a basic block builder with default parameters. The builder will57 // automatically append instructions to the basic block `BB'.58 IRBuilder<> builder(BB);59 60 // Get pointers to the constant `1'.61 Value *One = builder.getInt32(1);62 63 // Get pointers to the integer argument of the add1 function...64 assert(Add1F->arg_begin() != Add1F->arg_end()); // Make sure there's an arg65 Argument *ArgX = &*Add1F->arg_begin(); // Get the arg66 ArgX->setName("AnArg"); // Give it a nice symbolic name for fun.67 68 // Create the add instruction, inserting it into the end of BB.69 Value *Add = builder.CreateAdd(One, ArgX);70 71 // Create the return instruction and add it to the basic block72 builder.CreateRet(Add);73 74 return ThreadSafeModule(std::move(M), std::move(Context));75}76 77int main(int argc, char *argv[]) {78 // Initialize LLVM.79 InitLLVM X(argc, argv);80 81 InitializeNativeTarget();82 InitializeNativeTargetAsmPrinter();83 84 cl::ParseCommandLineOptions(argc, argv, "HowToUseLLJIT");85 ExitOnErr.setBanner(std::string(argv[0]) + ": ");86 87 // Create an LLJIT instance.88 auto J = ExitOnErr(LLJITBuilder().create());89 auto M = createDemoModule();90 91 ExitOnErr(J->addIRModule(std::move(M)));92 93 // Look up the JIT'd function, cast it to a function pointer, then call it.94 auto Add1Addr = ExitOnErr(J->lookup("add1"));95 int (*Add1)(int) = Add1Addr.toPtr<int(int)>();96 97 int Result = Add1(42);98 outs() << "add1(42) = " << Result << "\n";99 100 return 0;101}102