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         MF.initTargetMachineFunctionInfo(MF.getSubtarget());
70 
71         if (EmitFallbackDiag) {
72           const Function &F = MF.getFunction();
73           DiagnosticInfoISelFallback DiagFallback(F);
74           F.getContext().diagnose(DiagFallback);
75         }
76         return true;
77       }
78       return false;
79     }
80 
81   };
82 } // end anonymous namespace
83 
84 char ResetMachineFunction::ID = 0;
85 INITIALIZE_PASS(ResetMachineFunction, DEBUG_TYPE,
86                 "Reset machine function if ISel failed", false, false)
87 
88 MachineFunctionPass *
89 llvm::createResetMachineFunctionPass(bool EmitFallbackDiag = false,
90                                      bool AbortOnFailedISel = false) {
91   return new ResetMachineFunction(EmitFallbackDiag, AbortOnFailedISel);
92 }
93