//===-- SPIRVStripConvergentIntrinsics.cpp ----------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This pass trims convergence intrinsics as those were only useful when
// modifying the CFG during IR passes.
//
//===----------------------------------------------------------------------===//

#include "SPIRV.h"
#include "SPIRVSubtarget.h"
#include "SPIRVTargetMachine.h"
#include "SPIRVUtils.h"
#include "llvm/CodeGen/IntrinsicLowering.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/IntrinsicsSPIRV.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/LowerMemIntrinsics.h"

using namespace llvm;

namespace llvm {
void initializeSPIRVStripConvergentIntrinsicsPass(PassRegistry &);
}

class SPIRVStripConvergentIntrinsics : public FunctionPass {
public:
  static char ID;

  SPIRVStripConvergentIntrinsics() : FunctionPass(ID) {
    initializeSPIRVStripConvergentIntrinsicsPass(
        *PassRegistry::getPassRegistry());
  };

  virtual bool runOnFunction(Function &F) override {
    DenseSet<Instruction *> ToRemove;

    for (BasicBlock &BB : F) {
      for (Instruction &I : BB) {
        if (auto *II = dyn_cast<IntrinsicInst>(&I)) {
          if (II->getIntrinsicID() !=
                  Intrinsic::experimental_convergence_entry &&
              II->getIntrinsicID() !=
                  Intrinsic::experimental_convergence_loop &&
              II->getIntrinsicID() !=
                  Intrinsic::experimental_convergence_anchor) {
            continue;
          }

          II->replaceAllUsesWith(UndefValue::get(II->getType()));
          ToRemove.insert(II);
        } else if (auto *CI = dyn_cast<CallInst>(&I)) {
          auto OB = CI->getOperandBundle(LLVMContext::OB_convergencectrl);
          if (!OB.has_value())
            continue;

          auto *NewCall = CallBase::removeOperandBundle(
              CI, LLVMContext::OB_convergencectrl, CI);
          NewCall->copyMetadata(*CI);
          CI->replaceAllUsesWith(NewCall);
          ToRemove.insert(CI);
        }
      }
    }

    // All usages must be removed before their definition is removed.
    for (Instruction *I : ToRemove)
      I->eraseFromParent();

    return ToRemove.size() != 0;
  }
};

char SPIRVStripConvergentIntrinsics::ID = 0;
INITIALIZE_PASS(SPIRVStripConvergentIntrinsics, "strip-convergent-intrinsics",
                "SPIRV strip convergent intrinsics", false, false)

FunctionPass *llvm::createSPIRVStripConvergenceIntrinsicsPass() {
  return new SPIRVStripConvergentIntrinsics();
}