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//===--- HowToUseJIT.cpp - An example use of the JIT ----------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by Valery A. Khamenya and is distributed under the
// University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This small program provides an example of how to quickly build a small
// module with two functions and execute it with the JIT.
//
// Goal:
// The goal of this snippet is to create in the memory
// the LLVM module consisting of two functions as follow:
//
// int add1(int x) {
// return x+1;
// }
//
// int foo() {
// return add1(10);
// }
//
// then compile the module via JIT, then execute the `foo'
// function and return result to a driver, i.e. to a "host program".
//
// Some remarks and questions:
//
// - could we invoke some code using noname functions too?
// e.g. evaluate "foo()+foo()" without fears to introduce
// conflict of temporary function name with some real
// existing function name?
//
//===----------------------------------------------------------------------===//
#include "llvm/Module.h"
#include "llvm/Constants.h"
#include "llvm/Type.h"
#include "llvm/Instructions.h"
#include "llvm/ModuleProvider.h"
#include "llvm/ExecutionEngine/ExecutionEngine.h"
#include "llvm/ExecutionEngine/GenericValue.h"
#include <iostream>
using namespace llvm;
int main() {
// Create some module to put our function into it.
Module *M = new Module("test");
// Create the add1 function entry and insert this entry into module M. The
// function will have a return type of "int" and take an argument of "int".
// The '0' terminates the list of argument types.
Function *Add1F = M->getOrInsertFunction("add1", Type::IntTy, Type::IntTy, 0);
// Add a basic block to the function. As before, it automatically inserts
// because of the last argument.
BasicBlock *BB = new BasicBlock("EntryBlock", Add1F);
// Get pointers to the constant `1'.
Value *One = ConstantSInt::get(Type::IntTy, 1);
// Get pointers to the integer argument of the add1 function...
assert(Add1F->abegin() != Add1F->aend()); // Make sure there's an arg
Argument *ArgX = Add1F->abegin(); // Get the arg
ArgX->setName("AnArg"); // Give it a nice symbolic name for fun.
// Create the add instruction, inserting it into the end of BB.
Instruction *Add = BinaryOperator::createAdd(One, ArgX, "addresult", BB);
// Create the return instruction and add it to the basic block
new ReturnInst(Add, BB);
// Now, function add1 is ready.
// Now we going to create function `foo', which returns an int and takes no
// arguments.
Function *FooF = M->getOrInsertFunction("foo", Type::IntTy, 0);
// Add a basic block to the FooF function.
BB = new BasicBlock("EntryBlock", FooF);
// Get pointers to the constant `10'.
Value *Ten = ConstantSInt::get(Type::IntTy, 10);
// Pass Ten to the call call:
std::vector<Value*> Params;
Params.push_back(Ten);
CallInst * Add1CallRes = new CallInst(Add1F, Params, "add1", BB);
// Create the return instruction and add it to the basic block.
new ReturnInst(Add1CallRes, BB);
// Now we create the JIT.
ExistingModuleProvider* MP = new ExistingModuleProvider(M);
ExecutionEngine* EE = ExecutionEngine::create(MP, false);
std::cout << "We just constructed this LLVM module:\n\n" << *M;
std::cout << "\n\nRunning foo: " << std::flush;
// Call the `foo' function with no arguments:
std::vector<GenericValue> noargs;
GenericValue gv = EE->runFunction(FooF, noargs);
// Import result of execution:
std::cout << "Result: " << gv.IntVal << "\n";
return 0;
}
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