//===--- 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 condition function  and execute it with the JIT. 
//  (Modified from HowToUseJIT and Stacker/lib/compiler/StackerCompiler.cpp)
// 
//===------------------------------------------------------------------------===

// Goal: 
//  The goal of this snippet is to create in the memory
//  the LLVM module consisting functions as follow:
//
// int test(int x) {
//   if(1<=2) return 1;
//   return 2;
// }
// 
// then compile the module via JIT, then execute the `test' 
// 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 <iostream>

#include <llvm/Module.h>
#include <llvm/DerivedTypes.h>
#include <llvm/Constants.h>
#include <llvm/Instructions.h>
#include <llvm/ModuleProvider.h>

#include "llvm/ExecutionEngine/ExecutionEngine.h"
#include "llvm/ExecutionEngine/GenericValue.h"


using namespace llvm;

int main() {

  // Create some module to put our function into it.
  Module *M = new Module("test");


  // We are about to create the "test" function:
  Function *TestF;

  {
    // first create type for the single argument of test function: 
    // the type is 'int ()'

    // now create full type of the "test" function:
    FunctionType *TestT = FunctionType::get(Type::IntTy, // type of result
					    std::vector<const Type*>(),
					    /*not vararg*/false);
 
    // Now create the test function entry and 
    // insert this entry into module M
    // (By passing a module as the last parameter to the Function constructor,
    // it automatically gets appended to the Module.)
    TestF = new Function(TestT, 
			 Function::ExternalLinkage, // maybe too much
			 "test", M);

    // Add a basic block to the function... (again, it automatically inserts
    // because of the last argument.)
    BasicBlock *BB = new BasicBlock("EntryBlock of test function", TestF);
  
    // Get pointers to the constants ...
    Value *One = ConstantSInt::get(Type::IntTy, 1);
    Value *Two = ConstantSInt::get(Type::IntTy, 2);

    SetCondInst* CondInst 
      = new SetCondInst( Instruction::SetLE, One, Two );

    // Create the true_block
    BasicBlock* true_bb = new BasicBlock("true");

    // Create the return instruction and add it 
    // to the basic block for true case:
    true_bb->getInstList().push_back(new ReturnInst(One));
      
    // Create an exit block
    BasicBlock* exit_bb = new BasicBlock("false");
    exit_bb->getInstList().push_back(new ReturnInst(Two)); //////////////////////

    // Create a branch on the SetCond
    BranchInst* br_inst = 
      new BranchInst( true_bb, exit_bb, CondInst );

    BB->getInstList().push_back( br_inst );
    //    BB->getInstList().push_back(new ReturnInst(Two)); //////////////////////
  }

  // Now we going to create JIT ??
  ExistingModuleProvider* MP = new ExistingModuleProvider(M);
  ExecutionEngine* EE = ExecutionEngine::create( MP, true );

  // Call the `foo' function with no arguments:
  std::vector<GenericValue> noargs;
  GenericValue gv = EE->runFunction(TestF, noargs);

  // import result of execution:
  std::cout << "Result: " << gv.IntVal << std:: endl;

  return 0;
}
