LowerInvoke.cpp revision dce4a407a24b04eebc6a376f8e62b41aaa7b071f 
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"
25using namespace llvm;
26
27#define DEBUG_TYPE "lowerinvoke"
28
29STATISTIC(NumInvokes, "Number of invokes replaced");
30
31namespace {
32  class LowerInvoke : public FunctionPass {
33  public:
34    static char ID; // Pass identification, replacement for typeid
35    explicit LowerInvoke() : FunctionPass(ID) {
36      initializeLowerInvokePass(*PassRegistry::getPassRegistry());
37    }
38    bool runOnFunction(Function &F) override;
39  };
40}
41
42char LowerInvoke::ID = 0;
43INITIALIZE_PASS(LowerInvoke, "lowerinvoke",
44                "Lower invoke and unwind, for unwindless code generators",
45                false, false)
46
47char &llvm::LowerInvokePassID = LowerInvoke::ID;
48
49// Public Interface To the LowerInvoke pass.
50FunctionPass *llvm::createLowerInvokePass() {
51  return new LowerInvoke();
52}
53
54bool 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