chapter02-9.cpp

#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Verifier.h"
#include <vector>

using namespace llvm;

LLVMContext Context;
static Module *ModuleOb = new Module("my compiler", Context);
static std::vector<std::string> FunArgs;
typedef SmallVector<BasicBlock*, 16> BBList;
typedef SmallVector<Value*, 16> ValList;

Function *createFunc(IRBuilder<> &Builder, std::string Name) {
  std::vector<Type *> Integers(FunArgs.size(), Type::getInt32Ty(Context));
  FunctionType *funcType =
    llvm::FunctionType::get(Builder.getInt32Ty(),Integers, false);
  Function *fooFunc = llvm::Function::Create(
					     funcType, llvm::Function::ExternalLinkage, Name, ModuleOb);
  return fooFunc;
}

void setFuncArgs(Function *fooFunc, std::vector<std::string> FunArgs) {
  unsigned Idx = 0;
  Function::arg_iterator AI, AE;
  for(AI = fooFunc->arg_begin(), AE = fooFunc->arg_end(); AI != AE;
      ++AI, ++Idx)
    AI->setName(FunArgs[Idx]);
}

BasicBlock *createBB(Function *fooFunc, std::string Name) {
  return BasicBlock::Create(Context, Name, fooFunc);
}

GlobalVariable *createGlob(IRBuilder<> &Builder, std::string Name) {
  ModuleOb->getOrInsertGlobal(Name, Builder.getInt32Ty());
  GlobalVariable *gVar = ModuleOb->getNamedGlobal(Name);
  gVar->setLinkage(GlobalValue::CommonLinkage);
  gVar->setAlignment(4);
  return gVar;
}

Value *createArith(IRBuilder<> &Builder, Value *L, Value *R) {
  return Builder.CreateMul(L, R, "multmp");
}

Value *createLoop(IRBuilder<> &Builder, BBList List, ValList VL,
		  Value *StartVal, Value *EndVal) {
  BasicBlock *PreheaderBB = Builder.GetInsertBlock();
  Value *val = VL[0];
  BasicBlock *LoopBB = List[0];
  Builder.CreateBr(LoopBB);
  Builder.SetInsertPoint(LoopBB);
  PHINode *IndVar = Builder.CreatePHI(Type::getInt32Ty(Context), 2, "i");
  IndVar->addIncoming(StartVal, PreheaderBB);
  Value *Add = Builder.CreateAdd(val, Builder.getInt32(5), "addtmp");
  Value *StepVal = Builder.getInt32(1);
  Value *NextVal = Builder.CreateAdd(IndVar, StepVal, "nextval");
  Value *EndCond = Builder.CreateICmpULT(IndVar, EndVal, "endcond");
  EndCond = Builder.CreateICmpNE(EndCond, Builder.getInt32(0), "loopcond");
  BasicBlock *LoopEndBB = Builder.GetInsertBlock();
  BasicBlock *AfterBB = List[1];
  Builder.CreateCondBr(EndCond, LoopBB, AfterBB);
  Builder.SetInsertPoint(AfterBB);
  IndVar->addIncoming(NextVal, LoopEndBB);
  return Add;
}

int main(int argc, char *argv[])
{
  FunArgs.push_back("a");
  FunArgs.push_back("b");

  static IRBuilder<> Builder(Context);
  GlobalVariable *gVar = createGlob(Builder, "x");
  Function *fooFunc = createFunc(Builder, "foo");
  setFuncArgs(fooFunc, FunArgs);
  BasicBlock *entry = createBB(fooFunc, "entry");
  Builder.SetInsertPoint(entry);

  Function::arg_iterator AI = fooFunc->arg_begin();
  Value *Arg1 = AI++;
  Value *Arg2 = AI;
  Value *constant = Builder.getInt32(16);
  Value *val = createArith(Builder, Arg1, constant);
  ValList VL;
  VL.push_back(Arg1);

  BBList List;
  BasicBlock *LoopBB = createBB(fooFunc, "loop");
  BasicBlock *AfterBB = createBB(fooFunc, "afterloop");
  List.push_back(LoopBB);
  List.push_back(AfterBB);

  Value *StartVal = Builder.getInt32(1);
  Value *Res = createLoop(Builder, List, VL, StartVal, Arg2);
  
  Builder.CreateRet(Res);
  verifyFunction(*fooFunc);
  ModuleOb->print(llvm::outs(), nullptr);
  return 0;
}