lib/Transforms/Utils/LowerInvoke.cpp

   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 }