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#include "llvm/Target/TargetMachine.h"
26using namespace llvm;
27
28#define DEBUG_TYPE "reset-machine-function"
29
30STATISTIC(NumFunctionsReset, "Number of functions reset");
31STATISTIC(NumFunctionsVisited, "Number of functions visited");
32
33namespace {
34  class ResetMachineFunction : public MachineFunctionPass {
35    /// Tells whether or not this pass should emit a fallback
36    /// diagnostic when it resets a function.
37    bool EmitFallbackDiag;
38    /// Whether we should abort immediately instead of resetting the function.
39    bool AbortOnFailedISel;
40
41  public:
42    static char ID; // Pass identification, replacement for typeid
43    ResetMachineFunction(bool EmitFallbackDiag = false,
44                         bool AbortOnFailedISel = false)
45        : MachineFunctionPass(ID), EmitFallbackDiag(EmitFallbackDiag),
46          AbortOnFailedISel(AbortOnFailedISel) {}
47
48    StringRef getPassName() const override { return "ResetMachineFunction"; }
49
50    void getAnalysisUsage(AnalysisUsage &AU) const override {
51      AU.addPreserved<StackProtector>();
52      MachineFunctionPass::getAnalysisUsage(AU);
53    }
54
55    bool runOnMachineFunction(MachineFunction &MF) override {
56      ++NumFunctionsVisited;
57      // No matter what happened, whether we successfully selected the function
58      // or not, nothing is going to use the vreg types after us. Make sure they
59      // disappear.
60      auto ClearVRegTypesOnReturn =
61          make_scope_exit([&MF]() { MF.getRegInfo().clearVirtRegTypes(); });
62
63      if (MF.getProperties().hasProperty(
64              MachineFunctionProperties::Property::FailedISel)) {
65        if (AbortOnFailedISel)
66          report_fatal_error("Instruction selection failed");
67        LLVM_DEBUG(dbgs() << "Resetting: " << MF.getName() << '\n');
68        ++NumFunctionsReset;
69        MF.reset();
70        MF.initTargetMachineFunctionInfo(MF.getSubtarget());
71
72        const LLVMTargetMachine &TM = MF.getTarget();
73        // MRI callback for target specific initializations.
74        TM.registerMachineRegisterInfoCallback(MF);
75
76        if (EmitFallbackDiag) {
77          const Function &F = MF.getFunction();
78          DiagnosticInfoISelFallback DiagFallback(F);
79          F.getContext().diagnose(DiagFallback);
80        }
81        return true;
82      }
83      return false;
84    }
85
86  };
87} // end anonymous namespace
88
89char ResetMachineFunction::ID = 0;
90INITIALIZE_PASS(ResetMachineFunction, DEBUG_TYPE,
91                "Reset machine function if ISel failed", false, false)
92
93MachineFunctionPass *
94llvm::createResetMachineFunctionPass(bool EmitFallbackDiag = false,
95                                     bool AbortOnFailedISel = false) {
96  return new ResetMachineFunction(EmitFallbackDiag, AbortOnFailedISel);
97}
98