ResetMachineFunctionPass.cpp revision 360784 
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"
25using namespace llvm;
26
27#define DEBUG_TYPE "reset-machine-function"
28
29STATISTIC(NumFunctionsReset, "Number of functions reset");
30STATISTIC(NumFunctionsVisited, "Number of functions visited");
31
32namespace {
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
82char ResetMachineFunction::ID = 0;
83INITIALIZE_PASS(ResetMachineFunction, DEBUG_TYPE,
84                "Reset machine function if ISel failed", false, false)
85
86MachineFunctionPass *
87llvm::createResetMachineFunctionPass(bool EmitFallbackDiag = false,
88                                     bool AbortOnFailedISel = false) {
89  return new ResetMachineFunction(EmitFallbackDiag, AbortOnFailedISel);
90}
91