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/SmallVector.h"
18 #include "llvm/ADT/Statistic.h"
19 #include "llvm/IR/Instructions.h"
20 #include "llvm/IR/LLVMContext.h"
21 #include "llvm/IR/Module.h"
22 #include "llvm/Pass.h"
23 #include "llvm/Transforms/Utils.h"
24 using namespace llvm;
25 
26 #define DEBUG_TYPE "lowerinvoke"
27 
28 STATISTIC(NumInvokes, "Number of invokes replaced");
29 
30 namespace {
31   class LowerInvokeLegacyPass : public FunctionPass {
32   public:
33     static char ID; // Pass identification, replacement for typeid
34     explicit LowerInvokeLegacyPass() : FunctionPass(ID) {
35       initializeLowerInvokeLegacyPassPass(*PassRegistry::getPassRegistry());
36     }
37     bool runOnFunction(Function &F) override;
38   };
39 }
40 
41 char LowerInvokeLegacyPass::ID = 0;
42 INITIALIZE_PASS(LowerInvokeLegacyPass, "lowerinvoke",
43                 "Lower invoke and unwind, for unwindless code generators",
44                 false, false)
45 
46 static bool runImpl(Function &F) {
47   bool Changed = false;
48   for (BasicBlock &BB : F)
49     if (InvokeInst *II = dyn_cast<InvokeInst>(BB.getTerminator())) {
50       SmallVector<Value *, 16> CallArgs(II->arg_begin(), II->arg_end());
51       SmallVector<OperandBundleDef, 1> OpBundles;
52       II->getOperandBundlesAsDefs(OpBundles);
53       // Insert a normal call instruction...
54       CallInst *NewCall =
55           CallInst::Create(II->getCalledValue(), CallArgs, OpBundles, "", II);
56       NewCall->takeName(II);
57       NewCall->setCallingConv(II->getCallingConv());
58       NewCall->setAttributes(II->getAttributes());
59       NewCall->setDebugLoc(II->getDebugLoc());
60       II->replaceAllUsesWith(NewCall);
61 
62       // Insert an unconditional branch to the normal destination.
63       BranchInst::Create(II->getNormalDest(), II);
64 
65       // Remove any PHI node entries from the exception destination.
66       II->getUnwindDest()->removePredecessor(&BB);
67 
68       // Remove the invoke instruction now.
69       BB.getInstList().erase(II);
70 
71       ++NumInvokes;
72       Changed = true;
73     }
74   return Changed;
75 }
76 
77 bool LowerInvokeLegacyPass::runOnFunction(Function &F) {
78   return runImpl(F);
79 }
80 
81 namespace llvm {
82 char &LowerInvokePassID = LowerInvokeLegacyPass::ID;
83 
84 // Public Interface To the LowerInvoke pass.
85 FunctionPass *createLowerInvokePass() { return new LowerInvokeLegacyPass(); }
86 
87 PreservedAnalyses LowerInvokePass::run(Function &F,
88                                        FunctionAnalysisManager &AM) {
89   bool Changed = runImpl(F);
90   if (!Changed)
91     return PreservedAnalyses::all();
92 
93   return PreservedAnalyses::none();
94 }
95 }
96