1 //===--- examples/Fibonacci/fibonacci.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 build quickly a small module
11 // with function Fibonacci and execute it with the JIT.
13 // The goal of this snippet is to create in the memory the LLVM module
14 // consisting of one function as follow:
18 // return fib(x-1)+fib(x-2);
21 // Once we have this, we compile the module via JIT, then execute the `fib'
22 // function and return result to a driver, i.e. to a "host program".
24 //===----------------------------------------------------------------------===//
26 #include "llvm/Module.h"
27 #include "llvm/DerivedTypes.h"
28 #include "llvm/Constants.h"
29 #include "llvm/Instructions.h"
30 #include "llvm/ModuleProvider.h"
31 #include "llvm/Analysis/Verifier.h"
32 #include "llvm/ExecutionEngine/JIT.h"
33 #include "llvm/ExecutionEngine/Interpreter.h"
34 #include "llvm/ExecutionEngine/GenericValue.h"
38 static Function *CreateFibFunction(Module *M) {
39 // Create the fib function and insert it into module M. This function is said
40 // to return an int and take an int parameter.
41 Function *FibF = M->getOrInsertFunction("fib", Type::IntTy, Type::IntTy,
44 // Add a basic block to the function.
45 BasicBlock *BB = new BasicBlock("EntryBlock", FibF);
47 // Get pointers to the constants.
48 Value *One = ConstantSInt::get(Type::IntTy, 1);
49 Value *Two = ConstantSInt::get(Type::IntTy, 2);
51 // Get pointer to the integer argument of the add1 function...
52 Argument *ArgX = FibF->arg_begin(); // Get the arg.
53 ArgX->setName("AnArg"); // Give it a nice symbolic name for fun.
55 // Create the true_block.
56 BasicBlock *RetBB = new BasicBlock("return", FibF);
57 // Create an exit block.
58 BasicBlock* RecurseBB = new BasicBlock("recurse", FibF);
60 // Create the "if (arg < 2) goto exitbb"
61 Value *CondInst = BinaryOperator::createSetLE(ArgX, Two, "cond", BB);
62 new BranchInst(RetBB, RecurseBB, CondInst, BB);
65 new ReturnInst(One, RetBB);
68 Value *Sub = BinaryOperator::createSub(ArgX, One, "arg", RecurseBB);
69 CallInst *CallFibX1 = new CallInst(FibF, Sub, "fibx1", RecurseBB);
70 CallFibX1->setTailCall();
73 Sub = BinaryOperator::createSub(ArgX, Two, "arg", RecurseBB);
74 CallInst *CallFibX2 = new CallInst(FibF, Sub, "fibx2", RecurseBB);
75 CallFibX2->setTailCall();
79 Value *Sum = BinaryOperator::createAdd(CallFibX1, CallFibX2,
80 "addresult", RecurseBB);
82 // Create the return instruction and add it to the basic block
83 new ReturnInst(Sum, RecurseBB);
89 int main(int argc, char **argv) {
90 int n = argc > 1 ? atol(argv[1]) : 24;
92 // Create some module to put our function into it.
93 Module *M = new Module("test");
95 // We are about to create the "fib" function:
96 Function *FibF = CreateFibFunction(M);
98 // Now we going to create JIT
99 ExistingModuleProvider *MP = new ExistingModuleProvider(M);
100 ExecutionEngine *EE = ExecutionEngine::create(MP, false);
102 std::cerr << "verifying... ";
103 if (verifyModule(*M)) {
104 std::cerr << argv[0] << ": Error constructing function!\n";
109 std::cerr << "We just constructed this LLVM module:\n\n---------\n" << *M;
110 std::cerr << "---------\nstarting fibonacci(" << n << ") with JIT...\n";
112 // Call the Fibonacci function with argument n:
113 std::vector<GenericValue> Args(1);
115 GenericValue GV = EE->runFunction(FibF, Args);
117 // import result of execution
118 std::cout << "Result: " << GV.IntVal << "\n";