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