//===- SPIRVLowerBool.cpp - Lower instructions with bool operands ---------===//
//
//                     The LLVM/SPIRV Translator
//
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//===----------------------------------------------------------------------===//
//
// This file implements lowering instructions with bool operands.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "spvbool"

#include "SPIRVInternal.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InstVisitor.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Verifier.h"
#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"

using namespace llvm;
using namespace SPIRV;

namespace SPIRV {
cl::opt<bool> SPIRVLowerBoolValidate(
    "spvbool-validate",
    cl::desc("Validate module after lowering boolean instructions for SPIR-V"));

class SPIRVLowerBool : public ModulePass, public InstVisitor<SPIRVLowerBool> {
public:
  SPIRVLowerBool() : ModulePass(ID), Context(nullptr) {
    initializeSPIRVLowerBoolPass(*PassRegistry::getPassRegistry());
  }
  void replace(Instruction *I, Instruction *NewI) {
    NewI->takeName(I);
    I->replaceAllUsesWith(NewI);
    I->dropAllReferences();
    I->eraseFromParent();
  }
  bool isBoolType(Type *Ty) {
    if (Ty->isIntegerTy(1))
      return true;
    if (auto VT = dyn_cast<VectorType>(Ty))
      return isBoolType(VT->getElementType());
    return false;
  }
  virtual void visitTruncInst(TruncInst &I) {
    if (isBoolType(I.getType())) {
      auto Op = I.getOperand(0);
      auto And = BinaryOperator::CreateAnd(
          Op, getScalarOrVectorConstantInt(Op->getType(), 1, false), "", &I);
      auto Zero = getScalarOrVectorConstantInt(Op->getType(), 0, false);
      auto Cmp = new ICmpInst(&I, CmpInst::ICMP_NE, And, Zero);
      replace(&I, Cmp);
    }
  }
  virtual void visitZExtInst(ZExtInst &I) {
    auto Op = I.getOperand(0);
    if (isBoolType(Op->getType())) {
      auto Ty = I.getType();
      auto Zero = getScalarOrVectorConstantInt(Ty, 0, false);
      auto One = getScalarOrVectorConstantInt(Ty, 1, false);
      assert(Zero && One && "Couldn't create constant int");
      auto Sel = SelectInst::Create(Op, One, Zero, "", &I);
      replace(&I, Sel);
    }
  }
  virtual void visitSExtInst(SExtInst &I) {
    auto Op = I.getOperand(0);
    if (isBoolType(Op->getType())) {
      auto Ty = I.getType();
      auto Zero = getScalarOrVectorConstantInt(Ty, 0, false);
      auto One = getScalarOrVectorConstantInt(Ty, ~0, false);
      assert(Zero && One && "Couldn't create constant int");
      auto Sel = SelectInst::Create(Op, One, Zero, "", &I);
      replace(&I, Sel);
    }
  }
  bool runOnModule(Module &M) override {
    Context = &M.getContext();
    visit(M);

    if (SPIRVLowerBoolValidate) {
      LLVM_DEBUG(dbgs() << "After SPIRVLowerBool:\n" << M);
      std::string Err;
      raw_string_ostream ErrorOS(Err);
      if (verifyModule(M, &ErrorOS)) {
        Err = std::string("Fails to verify module: ") + Err;
        report_fatal_error(Err.c_str(), false);
      }
    }
    return true;
  }

  static char ID;

private:
  LLVMContext *Context;
};

char SPIRVLowerBool::ID = 0;
} // namespace SPIRV

INITIALIZE_PASS(SPIRVLowerBool, "spvbool",
                "Lower instructions with bool operands", false, false)

ModulePass *llvm::createSPIRVLowerBool() { return new SPIRVLowerBool(); }
