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/Passes.h"
22 #include "llvm/IR/DiagnosticInfo.h"
23 #include "llvm/Support/Debug.h"
24 using namespace llvm;
25 
26 #define DEBUG_TYPE "reset-machine-function"
27 
28 STATISTIC(NumFunctionsReset, "Number of functions reset");
29 
30 namespace {
31   class ResetMachineFunction : public MachineFunctionPass {
32     /// Tells whether or not this pass should emit a fallback
33     /// diagnostic when it resets a function.
34     bool EmitFallbackDiag;
35     /// Whether we should abort immediately instead of resetting the function.
36     bool AbortOnFailedISel;
37 
38   public:
39     static char ID; // Pass identification, replacement for typeid
40     ResetMachineFunction(bool EmitFallbackDiag = false,
41                          bool AbortOnFailedISel = false)
42         : MachineFunctionPass(ID), EmitFallbackDiag(EmitFallbackDiag),
43           AbortOnFailedISel(AbortOnFailedISel) {}
44 
45     StringRef getPassName() const override { return "ResetMachineFunction"; }
46 
47     bool runOnMachineFunction(MachineFunction &MF) override {
48       // No matter what happened, whether we successfully selected the function
49       // or not, nothing is going to use the vreg types after us. Make sure they
50       // disappear.
51       auto ClearVRegTypesOnReturn =
52           make_scope_exit([&MF]() { MF.getRegInfo().clearVirtRegTypes(); });
53 
54       if (MF.getProperties().hasProperty(
55               MachineFunctionProperties::Property::FailedISel)) {
56         if (AbortOnFailedISel)
57           report_fatal_error("Instruction selection failed");
58         LLVM_DEBUG(dbgs() << "Resetting: " << MF.getName() << '\n');
59         ++NumFunctionsReset;
60         MF.reset();
61         if (EmitFallbackDiag) {
62           const Function &F = MF.getFunction();
63           DiagnosticInfoISelFallback DiagFallback(F);
64           F.getContext().diagnose(DiagFallback);
65         }
66         return true;
67       }
68       return false;
69     }
70 
71   };
72 } // end anonymous namespace
73 
74 char ResetMachineFunction::ID = 0;
75 INITIALIZE_PASS(ResetMachineFunction, DEBUG_TYPE,
76                 "Reset machine function if ISel failed", false, false)
77 
78 MachineFunctionPass *
79 llvm::createResetMachineFunctionPass(bool EmitFallbackDiag = false,
80                                      bool AbortOnFailedISel = false) {
81   return new ResetMachineFunction(EmitFallbackDiag, AbortOnFailedISel);
82 }
83