ResetMachineFunctionPass.cpp

Go to the documentation of this file.

//===-- 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.
      llvm::scope_exit ClearVRegTypesOnReturn(
          [&MF]() { MF.getRegInfo().clearVirtRegTypes(); });
 
      if (!MF.getProperties().hasFailedISel())
        return false;
 
      if (AbortOnFailedISel)
        report_fatal_error("Instruction selection failed");
 
      LLVM_DEBUG(dbgs() << "Resetting: " << MF.getName() << '\n');
      ++NumFunctionsReset;
 
      if (MF.empty()) {
        // Nothing was materialized in the MachineFunction, so avoid the cost of
        // tearing down and rebuilding all of the per-function state. Just clear
        // the FailedISel bit so the SelectionDAG pipeline can proceed.
        auto &Props = MF.getProperties();
        Props.resetToInitial();
      } else {
        MF.reset();
        MF.initTargetMachineFunctionInfo(MF.getSubtarget());
 
        const TargetMachine &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;
    }
 
  };
} // 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);
}