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      1 //===-- ResetMachineFunctionPass.cpp - Reset Machine Function ----*- C++ -*-==//
      2 //
      3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
      4 // See https://llvm.org/LICENSE.txt for license information.
      5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
      6 //
      7 //===----------------------------------------------------------------------===//
      8 /// \file
      9 /// This file implements a pass that will conditionally reset a machine
     10 /// function as if it was just created. This is used to provide a fallback
     11 /// mechanism when GlobalISel fails, thus the condition for the reset to
     12 /// happen is that the MachineFunction has the FailedISel property.
     13 //===----------------------------------------------------------------------===//
     14 
     15 #include "llvm/ADT/ScopeExit.h"
     16 #include "llvm/ADT/Statistic.h"
     17 #include "llvm/CodeGen/MachineFunction.h"
     18 #include "llvm/CodeGen/MachineFunctionPass.h"
     19 #include "llvm/CodeGen/MachineRegisterInfo.h"
     20 #include "llvm/CodeGen/Passes.h"
     21 #include "llvm/CodeGen/StackProtector.h"
     22 #include "llvm/IR/DiagnosticInfo.h"
     23 #include "llvm/InitializePasses.h"
     24 #include "llvm/Support/Debug.h"
     25 using namespace llvm;
     26 
     27 #define DEBUG_TYPE "reset-machine-function"
     28 
     29 STATISTIC(NumFunctionsReset, "Number of functions reset");
     30 STATISTIC(NumFunctionsVisited, "Number of functions visited");
     31 
     32 namespace {
     33   class ResetMachineFunction : public MachineFunctionPass {
     34     /// Tells whether or not this pass should emit a fallback
     35     /// diagnostic when it resets a function.
     36     bool EmitFallbackDiag;
     37     /// Whether we should abort immediately instead of resetting the function.
     38     bool AbortOnFailedISel;
     39 
     40   public:
     41     static char ID; // Pass identification, replacement for typeid
     42     ResetMachineFunction(bool EmitFallbackDiag = false,
     43                          bool AbortOnFailedISel = false)
     44         : MachineFunctionPass(ID), EmitFallbackDiag(EmitFallbackDiag),
     45           AbortOnFailedISel(AbortOnFailedISel) {}
     46 
     47     StringRef getPassName() const override { return "ResetMachineFunction"; }
     48 
     49     void getAnalysisUsage(AnalysisUsage &AU) const override {
     50       AU.addPreserved<StackProtector>();
     51       MachineFunctionPass::getAnalysisUsage(AU);
     52     }
     53 
     54     bool runOnMachineFunction(MachineFunction &MF) override {
     55       ++NumFunctionsVisited;
     56       // No matter what happened, whether we successfully selected the function
     57       // or not, nothing is going to use the vreg types after us. Make sure they
     58       // disappear.
     59       auto ClearVRegTypesOnReturn =
     60           make_scope_exit([&MF]() { MF.getRegInfo().clearVirtRegTypes(); });
     61 
     62       if (MF.getProperties().hasProperty(
     63               MachineFunctionProperties::Property::FailedISel)) {
     64         if (AbortOnFailedISel)
     65           report_fatal_error("Instruction selection failed");
     66         LLVM_DEBUG(dbgs() << "Resetting: " << MF.getName() << '\n');
     67         ++NumFunctionsReset;
     68         MF.reset();
     69         if (EmitFallbackDiag) {
     70           const Function &F = MF.getFunction();
     71           DiagnosticInfoISelFallback DiagFallback(F);
     72           F.getContext().diagnose(DiagFallback);
     73         }
     74         return true;
     75       }
     76       return false;
     77     }
     78 
     79   };
     80 } // end anonymous namespace
     81 
     82 char ResetMachineFunction::ID = 0;
     83 INITIALIZE_PASS(ResetMachineFunction, DEBUG_TYPE,
     84                 "Reset machine function if ISel failed", false, false)
     85 
     86 MachineFunctionPass *
     87 llvm::createResetMachineFunctionPass(bool EmitFallbackDiag = false,
     88                                      bool AbortOnFailedISel = false) {
     89   return new ResetMachineFunction(EmitFallbackDiag, AbortOnFailedISel);
     90 }
     91