-/// ChangeToUnreachable - Insert an unreachable instruction before the specified
-/// instruction, making it and the rest of the code in the block dead.
-static void ChangeToUnreachable(Instruction *I, bool UseLLVMTrap) {
- BasicBlock *BB = I->getParent();
- // Loop over all of the successors, removing BB's entry from any PHI
- // nodes.
- for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
- (*SI)->removePredecessor(BB);
-
- // Insert a call to llvm.trap right before this. This turns the undefined
- // behavior into a hard fail instead of falling through into random code.
- if (UseLLVMTrap) {
- Function *TrapFn =
- Intrinsic::getDeclaration(BB->getParent()->getParent(), Intrinsic::trap);
- CallInst *CallTrap = CallInst::Create(TrapFn, "", I);
- CallTrap->setDebugLoc(I->getDebugLoc());
- }
- new UnreachableInst(I->getContext(), I);
-
- // All instructions after this are dead.
- BasicBlock::iterator BBI = I, BBE = BB->end();
- while (BBI != BBE) {
- if (!BBI->use_empty())
- BBI->replaceAllUsesWith(UndefValue::get(BBI->getType()));
- BB->getInstList().erase(BBI++);
- }
-}
-
-/// ChangeToCall - Convert the specified invoke into a normal call.
-static void ChangeToCall(InvokeInst *II) {
- BasicBlock *BB = II->getParent();
- SmallVector<Value*, 8> Args(II->op_begin(), II->op_end() - 3);
- CallInst *NewCall = CallInst::Create(II->getCalledValue(), Args, "", II);
- NewCall->takeName(II);
- NewCall->setCallingConv(II->getCallingConv());
- NewCall->setAttributes(II->getAttributes());
- NewCall->setDebugLoc(II->getDebugLoc());
- II->replaceAllUsesWith(NewCall);
-
- // Follow the call by a branch to the normal destination.
- BranchInst::Create(II->getNormalDest(), II);
-
- // Update PHI nodes in the unwind destination
- II->getUnwindDest()->removePredecessor(BB);
- BB->getInstList().erase(II);
-}
-
-static bool MarkAliveBlocks(BasicBlock *BB,
- SmallPtrSet<BasicBlock*, 128> &Reachable) {
-
- SmallVector<BasicBlock*, 128> Worklist;
- Worklist.push_back(BB);
- bool Changed = false;
- do {
- BB = Worklist.pop_back_val();
-
- if (!Reachable.insert(BB))
- continue;
-
- // Do a quick scan of the basic block, turning any obviously unreachable
- // instructions into LLVM unreachable insts. The instruction combining pass
- // canonicalizes unreachable insts into stores to null or undef.
- for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E;++BBI){
- if (CallInst *CI = dyn_cast<CallInst>(BBI)) {
- if (CI->doesNotReturn()) {
- // If we found a call to a no-return function, insert an unreachable
- // instruction after it. Make sure there isn't *already* one there
- // though.
- ++BBI;
- if (!isa<UnreachableInst>(BBI)) {
- // Don't insert a call to llvm.trap right before the unreachable.
- ChangeToUnreachable(BBI, false);
- Changed = true;
- }
- break;
- }
- }
-
- // Store to undef and store to null are undefined and used to signal that
- // they should be changed to unreachable by passes that can't modify the
- // CFG.
- if (StoreInst *SI = dyn_cast<StoreInst>(BBI)) {
- // Don't touch volatile stores.
- if (SI->isVolatile()) continue;
-
- Value *Ptr = SI->getOperand(1);
-
- if (isa<UndefValue>(Ptr) ||
- (isa<ConstantPointerNull>(Ptr) &&
- SI->getPointerAddressSpace() == 0)) {
- ChangeToUnreachable(SI, true);
- Changed = true;
- break;
- }
- }
- }
-
- // Turn invokes that call 'nounwind' functions into ordinary calls.
- if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
- Value *Callee = II->getCalledValue();
- if (isa<ConstantPointerNull>(Callee) || isa<UndefValue>(Callee)) {
- ChangeToUnreachable(II, true);
- Changed = true;
- } else if (II->doesNotThrow()) {
- ChangeToCall(II);
- Changed = true;
- }
- }
-
- Changed |= ConstantFoldTerminator(BB, true);
- for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
- Worklist.push_back(*SI);
- } while (!Worklist.empty());
- return Changed;
-}
-
-/// RemoveUnreachableBlocksFromFn - Remove blocks that are not reachable, even
-/// if they are in a dead cycle. Return true if a change was made, false
-/// otherwise.
-static bool RemoveUnreachableBlocksFromFn(Function &F) {
- SmallPtrSet<BasicBlock*, 128> Reachable;
- bool Changed = MarkAliveBlocks(F.begin(), Reachable);
-
- // If there are unreachable blocks in the CFG...
- if (Reachable.size() == F.size())
- return Changed;
-
- assert(Reachable.size() < F.size());
- NumSimpl += F.size()-Reachable.size();
-
- // Loop over all of the basic blocks that are not reachable, dropping all of
- // their internal references...
- for (Function::iterator BB = ++F.begin(), E = F.end(); BB != E; ++BB) {
- if (Reachable.count(BB))
- continue;
-
- for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
- if (Reachable.count(*SI))
- (*SI)->removePredecessor(BB);
- BB->dropAllReferences();
- }
-
- for (Function::iterator I = ++F.begin(); I != F.end();)
- if (!Reachable.count(I))
- I = F.getBasicBlockList().erase(I);
- else
- ++I;
-
- return true;
-}
-
-/// MergeEmptyReturnBlocks - If we have more than one empty (other than phi