1 //===--- examples/Fibonacci/fibonacci.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 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/LLVMContext.h"
27 #include "llvm/Module.h"
28 #include "llvm/DerivedTypes.h"
29 #include "llvm/Constants.h"
30 #include "llvm/Instructions.h"
31 #include "llvm/ModuleProvider.h"
32 #include "llvm/Analysis/Verifier.h"
33 #include "llvm/ExecutionEngine/JIT.h"
34 #include "llvm/ExecutionEngine/Interpreter.h"
35 #include "llvm/ExecutionEngine/GenericValue.h"
36 #include "llvm/Support/raw_ostream.h"
37 #include "llvm/Target/TargetSelect.h"
40 static Function *CreateFibFunction(Module *M, LLVMContext &Context) {
41 // Create the fib function and insert it into module M. This function is said
42 // to return an int and take an int parameter.
44 cast<Function>(M->getOrInsertFunction("fib", Type::getInt32Ty(Context),
45 Type::getInt32Ty(Context),
48 // Add a basic block to the function.
49 BasicBlock *BB = BasicBlock::Create(Context, "EntryBlock", FibF);
51 // Get pointers to the constants.
52 Value *One = ConstantInt::get(Type::getInt32Ty(Context), 1);
53 Value *Two = ConstantInt::get(Type::getInt32Ty(Context), 2);
55 // Get pointer to the integer argument of the add1 function...
56 Argument *ArgX = FibF->arg_begin(); // Get the arg.
57 ArgX->setName("AnArg"); // Give it a nice symbolic name for fun.
59 // Create the true_block.
60 BasicBlock *RetBB = BasicBlock::Create(Context, "return", FibF);
61 // Create an exit block.
62 BasicBlock* RecurseBB = BasicBlock::Create(Context, "recurse", FibF);
64 // Create the "if (arg <= 2) goto exitbb"
65 Value *CondInst = new ICmpInst(*BB, ICmpInst::ICMP_SLE, ArgX, Two, "cond");
66 BranchInst::Create(RetBB, RecurseBB, CondInst, BB);
69 ReturnInst::Create(Context, One, RetBB);
72 Value *Sub = BinaryOperator::CreateSub(ArgX, One, "arg", RecurseBB);
73 CallInst *CallFibX1 = CallInst::Create(FibF, Sub, "fibx1", RecurseBB);
74 CallFibX1->setTailCall();
77 Sub = BinaryOperator::CreateSub(ArgX, Two, "arg", RecurseBB);
78 CallInst *CallFibX2 = CallInst::Create(FibF, Sub, "fibx2", RecurseBB);
79 CallFibX2->setTailCall();
83 Value *Sum = BinaryOperator::CreateAdd(CallFibX1, CallFibX2,
84 "addresult", RecurseBB);
86 // Create the return instruction and add it to the basic block
87 ReturnInst::Create(Context, Sum, RecurseBB);
93 int main(int argc, char **argv) {
94 int n = argc > 1 ? atol(argv[1]) : 24;
96 InitializeNativeTarget();
99 // Create some module to put our function into it.
100 Module *M = new Module("test", Context);
102 // We are about to create the "fib" function:
103 Function *FibF = CreateFibFunction(M, Context);
105 // Now we going to create JIT
107 ExecutionEngine *EE = EngineBuilder(M).setErrorStr(&errStr).setEngineKind(EngineKind::JIT).create();
110 errs() << argv[0] << ": Failed to construct ExecutionEngine: " << errStr << "\n";
114 errs() << "verifying... ";
115 if (verifyModule(*M)) {
116 errs() << argv[0] << ": Error constructing function!\n";
121 errs() << "We just constructed this LLVM module:\n\n---------\n" << *M;
122 errs() << "---------\nstarting fibonacci(" << n << ") with JIT...\n";
124 // Call the Fibonacci function with argument n:
125 std::vector<GenericValue> Args(1);
126 Args[0].IntVal = APInt(32, n);
127 GenericValue GV = EE->runFunction(FibF, Args);
129 // import result of execution
130 outs() << "Result: " << GV.IntVal << "\n";