1 //===-- examples/HowToUseJIT/HowToUseJIT.cpp - An example use of the JIT --===//
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 #include "llvm/ExecutionEngine/Orc/LLJIT.h"
10 #include "llvm/IR/Function.h"
11 #include "llvm/IR/IRBuilder.h"
12 #include "llvm/IR/Module.h"
13 #include "llvm/Support/InitLLVM.h"
14 #include "llvm/Support/TargetSelect.h"
15 #include "llvm/Support/raw_ostream.h"
16 
17 using namespace llvm;
18 using namespace llvm::orc;
19 
20 ExitOnError ExitOnErr;
21 
22 ThreadSafeModule createDemoModule() {
23   auto Context = std::make_unique<LLVMContext>();
24   auto M = std::make_unique<Module>("test", *Context);
25 
26   // Create the add1 function entry and insert this entry into module M.  The
27   // function will have a return type of "int" and take an argument of "int".
28   Function *Add1F =
29       Function::Create(FunctionType::get(Type::getInt32Ty(*Context),
30                                          {Type::getInt32Ty(*Context)}, false),
31                        Function::ExternalLinkage, "add1", M.get());
32 
33   // Add a basic block to the function. As before, it automatically inserts
34   // because of the last argument.
35   BasicBlock *BB = BasicBlock::Create(*Context, "EntryBlock", Add1F);
36 
37   // Create a basic block builder with default parameters.  The builder will
38   // automatically append instructions to the basic block `BB'.
39   IRBuilder<> builder(BB);
40 
41   // Get pointers to the constant `1'.
42   Value *One = builder.getInt32(1);
43 
44   // Get pointers to the integer argument of the add1 function...
45   assert(Add1F->arg_begin() != Add1F->arg_end()); // Make sure there's an arg
46   Argument *ArgX = &*Add1F->arg_begin();          // Get the arg
47   ArgX->setName("AnArg"); // Give it a nice symbolic name for fun.
48 
49   // Create the add instruction, inserting it into the end of BB.
50   Value *Add = builder.CreateAdd(One, ArgX);
51 
52   // Create the return instruction and add it to the basic block
53   builder.CreateRet(Add);
54 
55   return ThreadSafeModule(std::move(M), std::move(Context));
56 }
57 
58 int main(int argc, char *argv[]) {
59   // Initialize LLVM.
60   InitLLVM X(argc, argv);
61 
62   InitializeNativeTarget();
63   InitializeNativeTargetAsmPrinter();
64 
65   cl::ParseCommandLineOptions(argc, argv, "HowToUseLLJIT");
66   ExitOnErr.setBanner(std::string(argv[0]) + ": ");
67 
68   // Create an LLJIT instance.
69   auto J = ExitOnErr(LLJITBuilder().create());
70   auto M = createDemoModule();
71 
72   ExitOnErr(J->addIRModule(std::move(M)));
73 
74   // Look up the JIT'd function, cast it to a function pointer, then call it.
75   auto Add1Sym = ExitOnErr(J->lookup("add1"));
76   int (*Add1)(int) = (int (*)(int))Add1Sym.getAddress();
77 
78   int Result = Add1(42);
79   outs() << "add1(42) = " << Result << "\n";
80 
81   return 0;
82 }
83