1 //===-- examples/HowToUseJIT/HowToUseJIT.cpp - An example use of the JIT --===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This small program provides an example of how to quickly build a small
11 // module with two functions and execute it with the JIT.
14 // The goal of this snippet is to create in the memory
15 // the LLVM module consisting of two functions as follow:
25 // then compile the module via JIT, then execute the `foo'
26 // function and return result to a driver, i.e. to a "host program".
28 // Some remarks and questions:
30 // - could we invoke some code using noname functions too?
31 // e.g. evaluate "foo()+foo()" without fears to introduce
32 // conflict of temporary function name with some real
33 // existing function name?
35 //===----------------------------------------------------------------------===//
37 #include "llvm/Module.h"
38 #include "llvm/Constants.h"
39 #include "llvm/DerivedTypes.h"
40 #include "llvm/Instructions.h"
41 #include "llvm/ModuleProvider.h"
42 #include "llvm/ExecutionEngine/JIT.h"
43 #include "llvm/ExecutionEngine/Interpreter.h"
44 #include "llvm/ExecutionEngine/GenericValue.h"
45 #include "llvm/Target/TargetSelect.h"
46 #include "llvm/Support/ManagedStatic.h"
47 #include "llvm/Support/raw_ostream.h"
52 InitializeNativeTarget();
54 // Create some module to put our function into it.
55 Module *M = new Module("test");
57 // Create the add1 function entry and insert this entry into module M. The
58 // function will have a return type of "int" and take an argument of "int".
59 // The '0' terminates the list of argument types.
61 cast<Function>(M->getOrInsertFunction("add1", Type::Int32Ty, Type::Int32Ty,
64 // Add a basic block to the function. As before, it automatically inserts
65 // because of the last argument.
66 BasicBlock *BB = BasicBlock::Create("EntryBlock", Add1F);
68 // Get pointers to the constant `1'.
69 Value *One = ConstantInt::get(Type::Int32Ty, 1);
71 // Get pointers to the integer argument of the add1 function...
72 assert(Add1F->arg_begin() != Add1F->arg_end()); // Make sure there's an arg
73 Argument *ArgX = Add1F->arg_begin(); // Get the arg
74 ArgX->setName("AnArg"); // Give it a nice symbolic name for fun.
76 // Create the add instruction, inserting it into the end of BB.
77 Instruction *Add = BinaryOperator::CreateAdd(One, ArgX, "addresult", BB);
79 // Create the return instruction and add it to the basic block
80 ReturnInst::Create(Add, BB);
82 // Now, function add1 is ready.
85 // Now we going to create function `foo', which returns an int and takes no
88 cast<Function>(M->getOrInsertFunction("foo", Type::Int32Ty, (Type *)0));
90 // Add a basic block to the FooF function.
91 BB = BasicBlock::Create("EntryBlock", FooF);
93 // Get pointers to the constant `10'.
94 Value *Ten = ConstantInt::get(Type::Int32Ty, 10);
96 // Pass Ten to the call call:
97 CallInst *Add1CallRes = CallInst::Create(Add1F, Ten, "add1", BB);
98 Add1CallRes->setTailCall(true);
100 // Create the return instruction and add it to the basic block.
101 ReturnInst::Create(Add1CallRes, BB);
103 // Now we create the JIT.
104 ExistingModuleProvider* MP = new ExistingModuleProvider(M);
105 ExecutionEngine* EE = ExecutionEngine::create(MP, false);
107 outs() << "We just constructed this LLVM module:\n\n" << *M;
108 outs() << "\n\nRunning foo: ";
111 // Call the `foo' function with no arguments:
112 std::vector<GenericValue> noargs;
113 GenericValue gv = EE->runFunction(FooF, noargs);
115 // Import result of execution:
116 outs() << "Result: " << gv.IntVal << "\n";
117 EE->freeMachineCodeForFunction(FooF);