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"
26 using namespace llvm;
27 
28 #define DEBUG_TYPE "reset-machine-function"
29 
30 STATISTIC(NumFunctionsReset, "Number of functions reset");
31 STATISTIC(NumFunctionsVisited, "Number of functions visited");
32 
33 namespace {
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 
89 char ResetMachineFunction::ID = 0;
90 INITIALIZE_PASS(ResetMachineFunction, DEBUG_TYPE,
91                 "Reset machine function if ISel failed", false, false)
92 
93 MachineFunctionPass *
94 llvm::createResetMachineFunctionPass(bool EmitFallbackDiag = false,
95                                      bool AbortOnFailedISel = false) {
96   return new ResetMachineFunction(EmitFallbackDiag, AbortOnFailedISel);
97 }
98