1 //===- LowerInvoke.cpp - Eliminate Invoke instructions --------------------===//
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 //
10 // This transformation is designed for use by code generators which do not yet
11 // support stack unwinding.  This pass converts 'invoke' instructions to 'call'
12 // instructions, so that any exception-handling 'landingpad' blocks become dead
13 // code (which can be removed by running the '-simplifycfg' pass afterwards).
14 //
15 //===----------------------------------------------------------------------===//
16 
17 #include "llvm/Transforms/Utils/LowerInvoke.h"
18 #include "llvm/ADT/SmallVector.h"
19 #include "llvm/ADT/Statistic.h"
20 #include "llvm/IR/Instructions.h"
21 #include "llvm/IR/LLVMContext.h"
22 #include "llvm/IR/Module.h"
23 #include "llvm/Pass.h"
24 #include "llvm/Transforms/Scalar.h"
25 using namespace llvm;
26 
27 #define DEBUG_TYPE "lowerinvoke"
28 
29 STATISTIC(NumInvokes, "Number of invokes replaced");
30 
31 namespace {
32   class LowerInvokeLegacyPass : public FunctionPass {
33   public:
34     static char ID; // Pass identification, replacement for typeid
35     explicit LowerInvokeLegacyPass() : FunctionPass(ID) {
36       initializeLowerInvokeLegacyPassPass(*PassRegistry::getPassRegistry());
37     }
38     bool runOnFunction(Function &F) override;
39   };
40 }
41 
42 char LowerInvokeLegacyPass::ID = 0;
43 INITIALIZE_PASS(LowerInvokeLegacyPass, "lowerinvoke",
44                 "Lower invoke and unwind, for unwindless code generators",
45                 false, false)
46 
47 static bool runImpl(Function &F) {
48   bool Changed = false;
49   for (BasicBlock &BB : F)
50     if (InvokeInst *II = dyn_cast<InvokeInst>(BB.getTerminator())) {
51       SmallVector<Value *, 16> CallArgs(II->op_begin(), II->op_end() - 3);
52       // Insert a normal call instruction...
53       CallInst *NewCall =
54           CallInst::Create(II->getCalledValue(), CallArgs, "", II);
55       NewCall->takeName(II);
56       NewCall->setCallingConv(II->getCallingConv());
57       NewCall->setAttributes(II->getAttributes());
58       NewCall->setDebugLoc(II->getDebugLoc());
59       II->replaceAllUsesWith(NewCall);
60 
61       // Insert an unconditional branch to the normal destination.
62       BranchInst::Create(II->getNormalDest(), II);
63 
64       // Remove any PHI node entries from the exception destination.
65       II->getUnwindDest()->removePredecessor(&BB);
66 
67       // Remove the invoke instruction now.
68       BB.getInstList().erase(II);
69 
70       ++NumInvokes;
71       Changed = true;
72     }
73   return Changed;
74 }
75 
76 bool LowerInvokeLegacyPass::runOnFunction(Function &F) {
77   return runImpl(F);
78 }
79 
80 namespace llvm {
81 char &LowerInvokePassID = LowerInvokeLegacyPass::ID;
82 
83 // Public Interface To the LowerInvoke pass.
84 FunctionPass *createLowerInvokePass() { return new LowerInvokeLegacyPass(); }
85 
86 PreservedAnalyses LowerInvokePass::run(Function &F,
87                                        FunctionAnalysisManager &AM) {
88   bool Changed = runImpl(F);
89   if (!Changed)
90     return PreservedAnalyses::all();
91 
92   return PreservedAnalyses::none();
93 }
94 }
95