examples/ModuleMaker/ModuleMaker.cpp

   1 //===- examples/ModuleMaker/ModuleMaker.cpp - Example project ---*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This programs is a simple example that creates an LLVM module "from scratch",
  10 // emitting it as a bitcode file to standard out.  This is just to show how
  11 // LLVM projects work and to demonstrate some of the LLVM APIs.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "llvm/Bitcode/BitcodeWriter.h"
  16 #include "llvm/IR/BasicBlock.h"
  17 #include "llvm/IR/Constants.h"
  18 #include "llvm/IR/DerivedTypes.h"
  19 #include "llvm/IR/Function.h"
  20 #include "llvm/IR/InstrTypes.h"
  21 #include "llvm/IR/Instruction.h"
  22 #include "llvm/IR/Instructions.h"
  23 #include "llvm/IR/LLVMContext.h"
  24 #include "llvm/IR/Module.h"
  25 #include "llvm/IR/Type.h"
  26 #include "llvm/Support/raw_ostream.h"
  27
  28 using namespace llvm;
  29
  30 int main() {
  31   LLVMContext Context;
  32
  33   // Create the "module" or "program" or "translation unit" to hold the
  34   // function
  35   Module *M = new Module("test", Context);
  36
  37   // Create the main function: first create the type 'int ()'
  38   FunctionType *FT =
  39     FunctionType::get(Type::getInt32Ty(Context), /*not vararg*/false);
  40
  41   // By passing a module as the last parameter to the Function constructor,
  42   // it automatically gets appended to the Module.
  43   Function *F = Function::Create(FT, Function::ExternalLinkage, "main", M);
  44
  45   // Add a basic block to the function... again, it automatically inserts
  46   // because of the last argument.
  47   BasicBlock *BB = BasicBlock::Create(Context, "EntryBlock", F);
  48
  49   // Get pointers to the constant integers...
  50   Value *Two = ConstantInt::get(Type::getInt32Ty(Context), 2);
  51   Value *Three = ConstantInt::get(Type::getInt32Ty(Context), 3);
  52
  53   // Create the add instruction... does not insert...
  54   Instruction *Add = BinaryOperator::Create(Instruction::Add, Two, Three,
  55                                             "addresult");
  56
  57   // explicitly insert it into the basic block...
  58   BB->getInstList().push_back(Add);
  59
  60   // Create the return instruction and add it to the basic block
  61   BB->getInstList().push_back(ReturnInst::Create(Context, Add));
  62
  63   // Output the bitcode file to stdout
  64   WriteBitcodeToFile(*M, outs());
  65
  66   // Delete the module and all of its contents.
  67   delete M;
  68   return 0;
  69 }