1 //===-- EHContGuardCatchret.cpp - Catchret target symbols -------*- 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 ///
9 /// \file
10 /// This file contains a machine function pass to insert a symbol before each
11 /// valid catchret target and store this in the MachineFunction's
12 /// CatchRetTargets vector. This will be used to emit the table of valid targets
13 /// used by EHCont Guard.
14 ///
15 //===----------------------------------------------------------------------===//
16 
17 #include "llvm/ADT/Statistic.h"
18 #include "llvm/CodeGen/MachineBasicBlock.h"
19 #include "llvm/CodeGen/MachineFunctionPass.h"
20 #include "llvm/CodeGen/MachineModuleInfo.h"
21 #include "llvm/CodeGen/Passes.h"
22 #include "llvm/InitializePasses.h"
23 
24 using namespace llvm;
25 
26 #define DEBUG_TYPE "ehcontguard-catchret"
27 
28 STATISTIC(EHContGuardCatchretTargets,
29           "Number of EHCont Guard catchret targets");
30 
31 namespace {
32 
33 /// MachineFunction pass to insert a symbol before each valid catchret target
34 /// and store these in the MachineFunction's CatchRetTargets vector.
35 class EHContGuardCatchret : public MachineFunctionPass {
36 public:
37   static char ID;
38 
39   EHContGuardCatchret() : MachineFunctionPass(ID) {
40     initializeEHContGuardCatchretPass(*PassRegistry::getPassRegistry());
41   }
42 
43   StringRef getPassName() const override {
44     return "EH Cont Guard catchret targets";
45   }
46 
47   bool runOnMachineFunction(MachineFunction &MF) override;
48 };
49 
50 } // end anonymous namespace
51 
52 char EHContGuardCatchret::ID = 0;
53 
54 INITIALIZE_PASS(EHContGuardCatchret, "EHContGuardCatchret",
55                 "Insert symbols at valid catchret targets for /guard:ehcont",
56                 false, false)
57 FunctionPass *llvm::createEHContGuardCatchretPass() {
58   return new EHContGuardCatchret();
59 }
60 
61 bool EHContGuardCatchret::runOnMachineFunction(MachineFunction &MF) {
62 
63   // Skip modules for which the ehcontguard flag is not set.
64   if (!MF.getMMI().getModule()->getModuleFlag("ehcontguard"))
65     return false;
66 
67   // Skip functions that do not have catchret
68   if (!MF.hasEHCatchret())
69     return false;
70 
71   bool Result = false;
72 
73   for (MachineBasicBlock &MBB : MF) {
74     if (MBB.isEHCatchretTarget()) {
75       MF.addCatchretTarget(MBB.getEHCatchretSymbol());
76       EHContGuardCatchretTargets++;
77       Result = true;
78     }
79   }
80 
81   return Result;
82 }
83