1 //===-- examples/HowToUseJIT/HowToUseJIT.cpp - An example use of the JIT --===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by Valery A. Khamenya and is distributed under the
6 // University of Illinois Open Source 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/Type.h"
40 #include "llvm/Instructions.h"
41 #include "llvm/ModuleProvider.h"
42 #include "llvm/ExecutionEngine/ExecutionEngine.h"
43 #include "llvm/ExecutionEngine/GenericValue.h"
48 // Create some module to put our function into it.
49 Module *M = new Module("test");
51 // Create the add1 function entry and insert this entry into module M. The
52 // function will have a return type of "int" and take an argument of "int".
53 // The '0' terminates the list of argument types.
54 Function *Add1F = M->getOrInsertFunction("add1", Type::IntTy, Type::IntTy,
57 // Add a basic block to the function. As before, it automatically inserts
58 // because of the last argument.
59 BasicBlock *BB = new BasicBlock("EntryBlock", Add1F);
61 // Get pointers to the constant `1'.
62 Value *One = ConstantSInt::get(Type::IntTy, 1);
64 // Get pointers to the integer argument of the add1 function...
65 assert(Add1F->arg_begin() != Add1F->arg_end()); // Make sure there's an arg
66 Argument *ArgX = Add1F->arg_begin(); // Get the arg
67 ArgX->setName("AnArg"); // Give it a nice symbolic name for fun.
69 // Create the add instruction, inserting it into the end of BB.
70 Instruction *Add = BinaryOperator::createAdd(One, ArgX, "addresult", BB);
72 // Create the return instruction and add it to the basic block
73 new ReturnInst(Add, BB);
75 // Now, function add1 is ready.
78 // Now we going to create function `foo', which returns an int and takes no
80 Function *FooF = M->getOrInsertFunction("foo", Type::IntTy, (Type *)0);
82 // Add a basic block to the FooF function.
83 BB = new BasicBlock("EntryBlock", FooF);
85 // Get pointers to the constant `10'.
86 Value *Ten = ConstantSInt::get(Type::IntTy, 10);
88 // Pass Ten to the call call:
89 std::vector<Value*> Params;
90 Params.push_back(Ten);
91 CallInst *Add1CallRes = new CallInst(Add1F, Params, "add1", BB);
92 Add1CallRes->setTailCall(true);
94 // Create the return instruction and add it to the basic block.
95 new ReturnInst(Add1CallRes, BB);
97 // Now we create the JIT.
98 ExistingModuleProvider* MP = new ExistingModuleProvider(M);
99 ExecutionEngine* EE = ExecutionEngine::create(MP, false);
101 std::cout << "We just constructed this LLVM module:\n\n" << *M;
102 std::cout << "\n\nRunning foo: " << std::flush;
104 // Call the `foo' function with no arguments:
105 std::vector<GenericValue> noargs;
106 GenericValue gv = EE->runFunction(FooF, noargs);
108 // Import result of execution:
109 std::cout << "Result: " << gv.IntVal << "\n";