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/Scalar.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/Support/CommandLine.h"
25 using namespace llvm;
26
27 #define DEBUG_TYPE "lowerinvoke"
28
29 STATISTIC(NumInvokes, "Number of invokes replaced");
30
31 namespace {
32 class LowerInvoke : public FunctionPass {
33 public:
34 static char ID; // Pass identification, replacement for typeid
LowerInvoke()35 explicit LowerInvoke() : FunctionPass(ID) {
36 initializeLowerInvokePass(*PassRegistry::getPassRegistry());
37 }
38 bool runOnFunction(Function &F) override;
39 };
40 }
41
42 char LowerInvoke::ID = 0;
43 INITIALIZE_PASS(LowerInvoke, "lowerinvoke",
44 "Lower invoke and unwind, for unwindless code generators",
45 false, false)
46
47 char &llvm::LowerInvokePassID = LowerInvoke::ID;
48
49 // Public Interface To the LowerInvoke pass.
createLowerInvokePass()50 FunctionPass *llvm::createLowerInvokePass() {
51 return new LowerInvoke();
52 }
53
runOnFunction(Function & F)54 bool LowerInvoke::runOnFunction(Function &F) {
55 bool Changed = false;
56 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
57 if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
58 SmallVector<Value*,16> CallArgs(II->op_begin(), II->op_end() - 3);
59 // Insert a normal call instruction...
60 CallInst *NewCall = CallInst::Create(II->getCalledValue(),
61 CallArgs, "", II);
62 NewCall->takeName(II);
63 NewCall->setCallingConv(II->getCallingConv());
64 NewCall->setAttributes(II->getAttributes());
65 NewCall->setDebugLoc(II->getDebugLoc());
66 II->replaceAllUsesWith(NewCall);
67
68 // Insert an unconditional branch to the normal destination.
69 BranchInst::Create(II->getNormalDest(), II);
70
71 // Remove any PHI node entries from the exception destination.
72 II->getUnwindDest()->removePredecessor(BB);
73
74 // Remove the invoke instruction now.
75 BB->getInstList().erase(II);
76
77 ++NumInvokes; Changed = true;
78 }
79 return Changed;
80 }
81