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 llvm::scope_exit ClearVRegTypesOnReturn(
61 [&MF]() { MF.getRegInfo().clearVirtRegTypes(); });
62
63 if (!MF.getProperties().hasFailedISel())
64 return false;
65
66 if (AbortOnFailedISel)
67 report_fatal_error(reason: "Instruction selection failed");
68
69 LLVM_DEBUG(dbgs() << "Resetting: " << MF.getName() << '\n');
70 ++NumFunctionsReset;
71
72 if (MF.empty()) {
73 // Nothing was materialized in the MachineFunction, so avoid the cost of
74 // tearing down and rebuilding all of the per-function state. Just clear
75 // the FailedISel bit so the SelectionDAG pipeline can proceed.
76 auto &Props = MF.getProperties();
77 Props.resetToInitial();
78 } else {
79 MF.reset();
80 MF.initTargetMachineFunctionInfo(STI: MF.getSubtarget());
81
82 const TargetMachine &TM = MF.getTarget();
83 // MRI callback for target specific initializations.
84 TM.registerMachineRegisterInfoCallback(MF);
85 }
86
87 if (EmitFallbackDiag) {
88 const Function &F = MF.getFunction();
89 DiagnosticInfoISelFallback DiagFallback(F);
90 F.getContext().diagnose(DI: DiagFallback);
91 }
92 return true;
93 }
94
95 };
96} // end anonymous namespace
97
98char ResetMachineFunction::ID = 0;
99INITIALIZE_PASS(ResetMachineFunction, DEBUG_TYPE,
100 "Reset machine function if ISel failed", false, false)
101
102MachineFunctionPass *
103llvm::createResetMachineFunctionPass(bool EmitFallbackDiag = false,
104 bool AbortOnFailedISel = false) {
105 return new ResetMachineFunction(EmitFallbackDiag, AbortOnFailedISel);
106}
107