1//===- LowerInvoke.cpp - Eliminate Invoke instructions --------------------===//
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// This transformation is designed for use by code generators which do not yet
10// support stack unwinding. This pass converts 'invoke' instructions to 'call'
11// instructions, so that any exception-handling 'landingpad' blocks become dead
12// code (which can be removed by running the '-simplifycfg' pass afterwards).
13//
14//===----------------------------------------------------------------------===//
15
16#include "llvm/Transforms/Utils/LowerInvoke.h"
17#include "llvm/ADT/Statistic.h"
18#include "llvm/IR/Instructions.h"
19#include "llvm/InitializePasses.h"
20#include "llvm/Pass.h"
21#include "llvm/Transforms/Utils.h"
22#include "llvm/Transforms/Utils/Local.h"
23using namespace llvm;
24
25#define DEBUG_TYPE "lower-invoke"
26
27STATISTIC(NumInvokes, "Number of invokes replaced");
28
29namespace {
30class LowerInvokeLegacyPass : public FunctionPass {
31public:
32 static char ID; // Pass identification, replacement for typeid
33 explicit LowerInvokeLegacyPass() : FunctionPass(ID) {
34 initializeLowerInvokeLegacyPassPass(*PassRegistry::getPassRegistry());
35 }
36 bool runOnFunction(Function &F) override;
37};
38} // namespace
39
40char LowerInvokeLegacyPass::ID = 0;
41INITIALIZE_PASS(LowerInvokeLegacyPass, "lowerinvoke",
42 "Lower invoke and unwind, for unwindless code generators",
43 false, false)
44
45static bool runImpl(Function &F) {
46 bool Changed = false;
47 for (BasicBlock &BB : F)
48 if (InvokeInst *II = dyn_cast<InvokeInst>(Val: BB.getTerminator())) {
49 CallInst *NewCall = createCallMatchingInvoke(II);
50 NewCall->takeName(V: II);
51 NewCall->insertBefore(InsertPos: II->getIterator());
52 II->replaceAllUsesWith(V: NewCall);
53
54 // Insert an unconditional branch to the normal destination.
55 UncondBrInst::Create(Target: II->getNormalDest(), InsertBefore: II->getIterator());
56
57 // Remove any PHI node entries from the exception destination.
58 II->getUnwindDest()->removePredecessor(Pred: &BB);
59
60 // Remove the invoke instruction now.
61 II->eraseFromParent();
62
63 ++NumInvokes;
64 Changed = true;
65 }
66 return Changed;
67}
68
69bool LowerInvokeLegacyPass::runOnFunction(Function &F) {
70 return runImpl(F);
71}
72
73char &llvm::LowerInvokePassID = LowerInvokeLegacyPass::ID;
74
75// Public Interface To the LowerInvoke pass.
76FunctionPass *llvm::createLowerInvokePass() {
77 return new LowerInvokeLegacyPass();
78}
79
80PreservedAnalyses LowerInvokePass::run(Function &F,
81 FunctionAnalysisManager &AM) {
82 bool Changed = runImpl(F);
83 if (!Changed)
84 return PreservedAnalyses::all();
85
86 return PreservedAnalyses::none();
87}
88