//===-- ResetMachineFunctionPass.cpp - Reset Machine Function ----*- 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

//

//===----------------------------------------------------------------------===//

/// \file

/// This file implements a pass that will conditionally reset a machine

/// function as if it was just created. This is used to provide a fallback

/// mechanism when GlobalISel fails, thus the condition for the reset to

/// happen is that the MachineFunction has the FailedISel property.

//===----------------------------------------------------------------------===//

#include "llvm/ADT/ScopeExit.h"

#include "llvm/ADT/Statistic.h"

#include "llvm/CodeGen/MachineFunction.h"

#include "llvm/CodeGen/MachineFunctionPass.h"

#include "llvm/CodeGen/MachineRegisterInfo.h"

#include "llvm/CodeGen/Passes.h"

#include "llvm/CodeGen/StackProtector.h"

#include "llvm/IR/DiagnosticInfo.h"

#include "llvm/InitializePasses.h"

#include "llvm/Support/Debug.h"

#include "llvm/Target/TargetMachine.h"

using namespace llvm;

#define DEBUG_TYPE "reset-machine-function"

STATISTIC(NumFunctionsReset, "Number of functions reset");

STATISTIC(NumFunctionsVisited, "Number of functions visited");

namespace {

  class ResetMachineFunction : public MachineFunctionPass {

    /// Tells whether or not this pass should emit a fallback

    /// diagnostic when it resets a function.

    bool EmitFallbackDiag;

    /// Whether we should abort immediately instead of resetting the function.

    bool AbortOnFailedISel;

  public:

    static char ID; // Pass identification, replacement for typeid

    ResetMachineFunction(bool EmitFallbackDiag = false,

                         bool AbortOnFailedISel = false)

        : MachineFunctionPass(ID), EmitFallbackDiag(EmitFallbackDiag),

          AbortOnFailedISel(AbortOnFailedISel) {}

    StringRef getPassName() const override { return "ResetMachineFunction"; }

    void getAnalysisUsage(AnalysisUsage &AU) const override {

      AU.addPreserved<StackProtector>();

      MachineFunctionPass::getAnalysisUsage(AU);

    }

    bool runOnMachineFunction(MachineFunction &MF) override {

      ++NumFunctionsVisited;

      // No matter what happened, whether we successfully selected the function

      // or not, nothing is going to use the vreg types after us. Make sure they

      // disappear.

      auto ClearVRegTypesOnReturn =

          make_scope_exit([&MF]() { MF.getRegInfo().clearVirtRegTypes(); });

      if (MF.getProperties().hasProperty(

              MachineFunctionProperties::Property::FailedISel)) {

        if (AbortOnFailedISel)

          report_fatal_error("Instruction selection failed");

        LLVM_DEBUG(dbgs() << "Resetting: " << MF.getName() << '\n');

        ++NumFunctionsReset;

        MF.reset();

        MF.initTargetMachineFunctionInfo(MF.getSubtarget());

        const LLVMTargetMachine &TM = MF.getTarget();

        // MRI callback for target specific initializations.

        TM.registerMachineRegisterInfoCallback(MF);

        if (EmitFallbackDiag) {

          const Function &F = MF.getFunction();

          DiagnosticInfoISelFallback DiagFallback(F);

          F.getContext().diagnose(DiagFallback);

        }

        return true;

      }

      return false;

    }

  };

} // end anonymous namespace

char ResetMachineFunction::ID = 0;

INITIALIZE_PASS(ResetMachineFunction, DEBUG_TYPE,

                "Reset machine function if ISel failed", false, false)

MachineFunctionPass *

llvm::createResetMachineFunctionPass(bool EmitFallbackDiag = false,

                                     bool AbortOnFailedISel = false) {

  return new ResetMachineFunction(EmitFallbackDiag, AbortOnFailedISel);

}