-
-/// rewriteExpensiveInvoke - Insert code and hack the function to replace the
-/// specified invoke instruction with a call.
-void LowerInvoke::rewriteExpensiveInvoke(InvokeInst *II, unsigned InvokeNo,
- AllocaInst *InvokeNum,
- AllocaInst *StackPtr,
- SwitchInst *CatchSwitch) {
- ConstantInt *InvokeNoC = ConstantInt::get(Type::getInt32Ty(II->getContext()),
- InvokeNo);
-
- // If the unwind edge has phi nodes, split the edge.
- if (isa<PHINode>(II->getUnwindDest()->begin())) {
- SplitCriticalEdge(II, 1, this);
-
- // If there are any phi nodes left, they must have a single predecessor.
- while (PHINode *PN = dyn_cast<PHINode>(II->getUnwindDest()->begin())) {
- PN->replaceAllUsesWith(PN->getIncomingValue(0));
- PN->eraseFromParent();
- }
- }
-
- // Insert a store of the invoke num before the invoke and store zero into the
- // location afterward.
- new StoreInst(InvokeNoC, InvokeNum, true, II); // volatile
-
- // Insert a store of the stack ptr before the invoke, so we can restore it
- // later in the exception case.
- CallInst* StackSaveRet = CallInst::Create(StackSaveFn, "ssret", II);
- new StoreInst(StackSaveRet, StackPtr, true, II); // volatile
-
- BasicBlock::iterator NI = II->getNormalDest()->getFirstInsertionPt();
- // nonvolatile.
- new StoreInst(Constant::getNullValue(Type::getInt32Ty(II->getContext())),
- InvokeNum, false, NI);
-
- Instruction* StackPtrLoad =
- new LoadInst(StackPtr, "stackptr.restore", true,
- II->getUnwindDest()->getFirstInsertionPt());
- CallInst::Create(StackRestoreFn, StackPtrLoad, "")->insertAfter(StackPtrLoad);
-
- // Add a switch case to our unwind block.
- CatchSwitch->addCase(InvokeNoC, II->getUnwindDest());
-
- // Insert a normal call instruction.
- SmallVector<Value*,16> CallArgs(II->op_begin(), II->op_end() - 3);
- CallInst *NewCall = CallInst::Create(II->getCalledValue(),
- CallArgs, "", II);
- NewCall->takeName(II);
- NewCall->setCallingConv(II->getCallingConv());
- NewCall->setAttributes(II->getAttributes());
- NewCall->setDebugLoc(II->getDebugLoc());
- II->replaceAllUsesWith(NewCall);
-
- // Replace the invoke with an uncond branch.
- BranchInst::Create(II->getNormalDest(), NewCall->getParent());
- II->eraseFromParent();
-}
-
-/// MarkBlocksLiveIn - Insert BB and all of its predescessors into LiveBBs until
-/// we reach blocks we've already seen.
-static void MarkBlocksLiveIn(BasicBlock *BB, std::set<BasicBlock*> &LiveBBs) {
- if (!LiveBBs.insert(BB).second) return; // already been here.
-
- for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
- MarkBlocksLiveIn(*PI, LiveBBs);
-}
-
-// First thing we need to do is scan the whole function for values that are
-// live across unwind edges. Each value that is live across an unwind edge
-// we spill into a stack location, guaranteeing that there is nothing live
-// across the unwind edge. This process also splits all critical edges
-// coming out of invoke's.
-void LowerInvoke::
-splitLiveRangesLiveAcrossInvokes(SmallVectorImpl<InvokeInst*> &Invokes) {
- // First step, split all critical edges from invoke instructions.
- for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
- InvokeInst *II = Invokes[i];
- SplitCriticalEdge(II, 0, this);
- SplitCriticalEdge(II, 1, this);
- assert(!isa<PHINode>(II->getNormalDest()) &&
- !isa<PHINode>(II->getUnwindDest()) &&
- "critical edge splitting left single entry phi nodes?");
- }
-
- Function *F = Invokes.back()->getParent()->getParent();
-
- // To avoid having to handle incoming arguments specially, we lower each arg
- // to a copy instruction in the entry block. This ensures that the argument
- // value itself cannot be live across the entry block.
- BasicBlock::iterator AfterAllocaInsertPt = F->begin()->begin();
- while (isa<AllocaInst>(AfterAllocaInsertPt) &&
- isa<ConstantInt>(cast<AllocaInst>(AfterAllocaInsertPt)->getArraySize()))
- ++AfterAllocaInsertPt;
- for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
- AI != E; ++AI) {
- Type *Ty = AI->getType();
- // Aggregate types can't be cast, but are legal argument types, so we have
- // to handle them differently. We use an extract/insert pair as a
- // lightweight method to achieve the same goal.
- if (isa<StructType>(Ty) || isa<ArrayType>(Ty) || isa<VectorType>(Ty)) {
- Instruction *EI = ExtractValueInst::Create(AI, 0, "",AfterAllocaInsertPt);
- Instruction *NI = InsertValueInst::Create(AI, EI, 0);
- NI->insertAfter(EI);
- AI->replaceAllUsesWith(NI);
- // Set the operand of the instructions back to the AllocaInst.
- EI->setOperand(0, AI);
- NI->setOperand(0, AI);
- } else {
- // This is always a no-op cast because we're casting AI to AI->getType()
- // so src and destination types are identical. BitCast is the only
- // possibility.
- CastInst *NC = new BitCastInst(
- AI, AI->getType(), AI->getName()+".tmp", AfterAllocaInsertPt);
- AI->replaceAllUsesWith(NC);
- // Set the operand of the cast instruction back to the AllocaInst.
- // Normally it's forbidden to replace a CastInst's operand because it
- // could cause the opcode to reflect an illegal conversion. However,
- // we're replacing it here with the same value it was constructed with.
- // We do this because the above replaceAllUsesWith() clobbered the
- // operand, but we want this one to remain.
- NC->setOperand(0, AI);
- }
- }
-
- // Finally, scan the code looking for instructions with bad live ranges.
- for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
- for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ++II) {
- // Ignore obvious cases we don't have to handle. In particular, most
- // instructions either have no uses or only have a single use inside the
- // current block. Ignore them quickly.
- Instruction *Inst = II;
- if (Inst->use_empty()) continue;
- if (Inst->hasOneUse() &&
- cast<Instruction>(Inst->use_back())->getParent() == BB &&
- !isa<PHINode>(Inst->use_back())) continue;
-
- // If this is an alloca in the entry block, it's not a real register
- // value.
- if (AllocaInst *AI = dyn_cast<AllocaInst>(Inst))
- if (isa<ConstantInt>(AI->getArraySize()) && BB == F->begin())
- continue;
-
- // Avoid iterator invalidation by copying users to a temporary vector.
- SmallVector<Instruction*,16> Users;
- for (Value::use_iterator UI = Inst->use_begin(), E = Inst->use_end();
- UI != E; ++UI) {
- Instruction *User = cast<Instruction>(*UI);
- if (User->getParent() != BB || isa<PHINode>(User))
- Users.push_back(User);
- }
-
- // Scan all of the uses and see if the live range is live across an unwind
- // edge. If we find a use live across an invoke edge, create an alloca
- // and spill the value.
- std::set<InvokeInst*> InvokesWithStoreInserted;
-
- // Find all of the blocks that this value is live in.
- std::set<BasicBlock*> LiveBBs;
- LiveBBs.insert(Inst->getParent());
- while (!Users.empty()) {
- Instruction *U = Users.back();
- Users.pop_back();
-
- if (!isa<PHINode>(U)) {
- MarkBlocksLiveIn(U->getParent(), LiveBBs);
- } else {
- // Uses for a PHI node occur in their predecessor block.
- PHINode *PN = cast<PHINode>(U);
- for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
- if (PN->getIncomingValue(i) == Inst)
- MarkBlocksLiveIn(PN->getIncomingBlock(i), LiveBBs);
- }
- }
-
- // Now that we know all of the blocks that this thing is live in, see if
- // it includes any of the unwind locations.
- bool NeedsSpill = false;
- for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
- BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest();
- if (UnwindBlock != BB && LiveBBs.count(UnwindBlock)) {
- NeedsSpill = true;
- }
- }
-
- // If we decided we need a spill, do it.
- if (NeedsSpill) {
- ++NumSpilled;
- DemoteRegToStack(*Inst, true);
- }
- }
-}
-
-bool LowerInvoke::insertExpensiveEHSupport(Function &F) {
- SmallVector<ReturnInst*,16> Returns;
- SmallVector<InvokeInst*,16> Invokes;
- UnreachableInst* UnreachablePlaceholder = 0;
-
- for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
- if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
- // Remember all return instructions in case we insert an invoke into this
- // function.
- Returns.push_back(RI);
- } else if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
- Invokes.push_back(II);
- }
-
- if (Invokes.empty()) return false;
-
- NumInvokes += Invokes.size();
-
- // TODO: This is not an optimal way to do this. In particular, this always
- // inserts setjmp calls into the entries of functions with invoke instructions
- // even though there are possibly paths through the function that do not
- // execute any invokes. In particular, for functions with early exits, e.g.
- // the 'addMove' method in hexxagon, it would be nice to not have to do the
- // setjmp stuff on the early exit path. This requires a bit of dataflow, but
- // would not be too hard to do.
-
- // If we have an invoke instruction, insert a setjmp that dominates all
- // invokes. After the setjmp, use a cond branch that goes to the original
- // code path on zero, and to a designated 'catch' block of nonzero.
- Value *OldJmpBufPtr = 0;
- if (!Invokes.empty()) {
- // First thing we need to do is scan the whole function for values that are
- // live across unwind edges. Each value that is live across an unwind edge
- // we spill into a stack location, guaranteeing that there is nothing live
- // across the unwind edge. This process also splits all critical edges
- // coming out of invoke's.
- splitLiveRangesLiveAcrossInvokes(Invokes);
-
- BasicBlock *EntryBB = F.begin();
-
- // Create an alloca for the incoming jump buffer ptr and the new jump buffer
- // that needs to be restored on all exits from the function. This is an
- // alloca because the value needs to be live across invokes.
- unsigned Align = STTI ? STTI->getJumpBufAlignment() : 0;
- AllocaInst *JmpBuf =
- new AllocaInst(JBLinkTy, 0, Align,
- "jblink", F.begin()->begin());
-
- Value *Idx[] = { Constant::getNullValue(Type::getInt32Ty(F.getContext())),
- ConstantInt::get(Type::getInt32Ty(F.getContext()), 1) };
- OldJmpBufPtr = GetElementPtrInst::Create(JmpBuf, Idx, "OldBuf",
- EntryBB->getTerminator());
-
- // Copy the JBListHead to the alloca.
- Value *OldBuf = new LoadInst(JBListHead, "oldjmpbufptr", true,
- EntryBB->getTerminator());
- new StoreInst(OldBuf, OldJmpBufPtr, true, EntryBB->getTerminator());
-
- // Add the new jumpbuf to the list.
- new StoreInst(JmpBuf, JBListHead, true, EntryBB->getTerminator());
-
- // Create the catch block. The catch block is basically a big switch
- // statement that goes to all of the invoke catch blocks.
- BasicBlock *CatchBB =
- BasicBlock::Create(F.getContext(), "setjmp.catch", &F);
-
- // Create an alloca which keeps track of the stack pointer before every
- // invoke, this allows us to properly restore the stack pointer after
- // long jumping.
- AllocaInst *StackPtr = new AllocaInst(Type::getInt8PtrTy(F.getContext()), 0,
- "stackptr", EntryBB->begin());
-
- // Create an alloca which keeps track of which invoke is currently
- // executing. For normal calls it contains zero.
- AllocaInst *InvokeNum = new AllocaInst(Type::getInt32Ty(F.getContext()), 0,
- "invokenum",EntryBB->begin());
- new StoreInst(ConstantInt::get(Type::getInt32Ty(F.getContext()), 0),
- InvokeNum, true, EntryBB->getTerminator());
-
- // Insert a load in the Catch block, and a switch on its value. By default,
- // we go to a block that just does an unwind (which is the correct action
- // for a standard call). We insert an unreachable instruction here and
- // modify the block to jump to the correct unwinding pad later.
- BasicBlock *UnwindBB = BasicBlock::Create(F.getContext(), "unwindbb", &F);
- UnreachablePlaceholder = new UnreachableInst(F.getContext(), UnwindBB);
-
- Value *CatchLoad = new LoadInst(InvokeNum, "invoke.num", true, CatchBB);
- SwitchInst *CatchSwitch =
- SwitchInst::Create(CatchLoad, UnwindBB, Invokes.size(), CatchBB);
-
- // Now that things are set up, insert the setjmp call itself.
-
- // Split the entry block to insert the conditional branch for the setjmp.
- BasicBlock *ContBlock = EntryBB->splitBasicBlock(EntryBB->getTerminator(),
- "setjmp.cont");
-
- Idx[1] = ConstantInt::get(Type::getInt32Ty(F.getContext()), 0);
- Value *JmpBufPtr = GetElementPtrInst::Create(JmpBuf, Idx, "TheJmpBuf",
- EntryBB->getTerminator());
- JmpBufPtr = new BitCastInst(JmpBufPtr,
- Type::getInt8PtrTy(F.getContext()),
- "tmp", EntryBB->getTerminator());
- Value *SJRet = CallInst::Create(SetJmpFn, JmpBufPtr, "sjret",
- EntryBB->getTerminator());
-
- // Compare the return value to zero.
- Value *IsNormal = new ICmpInst(EntryBB->getTerminator(),
- ICmpInst::ICMP_EQ, SJRet,
- Constant::getNullValue(SJRet->getType()),
- "notunwind");
- // Nuke the uncond branch.
- EntryBB->getTerminator()->eraseFromParent();
-
- // Put in a new condbranch in its place.
- BranchInst::Create(ContBlock, CatchBB, IsNormal, EntryBB);
-
- // At this point, we are all set up, rewrite each invoke instruction.
- for (unsigned i = 0, e = Invokes.size(); i != e; ++i)
- rewriteExpensiveInvoke(Invokes[i], i+1, InvokeNum, StackPtr, CatchSwitch);
- }
-
- // We know that there is at least one unwind.
-
- // Create three new blocks, the block to load the jmpbuf ptr and compare
- // against null, the block to do the longjmp, and the error block for if it
- // is null. Add them at the end of the function because they are not hot.
- BasicBlock *UnwindHandler = BasicBlock::Create(F.getContext(),
- "dounwind", &F);
- BasicBlock *UnwindBlock = BasicBlock::Create(F.getContext(), "unwind", &F);
- BasicBlock *TermBlock = BasicBlock::Create(F.getContext(), "unwinderror", &F);
-
- // If this function contains an invoke, restore the old jumpbuf ptr.
- Value *BufPtr;
- if (OldJmpBufPtr) {
- // Before the return, insert a copy from the saved value to the new value.
- BufPtr = new LoadInst(OldJmpBufPtr, "oldjmpbufptr", UnwindHandler);
- new StoreInst(BufPtr, JBListHead, UnwindHandler);
- } else {
- BufPtr = new LoadInst(JBListHead, "ehlist", UnwindHandler);
- }
-
- // Load the JBList, if it's null, then there was no catch!
- Value *NotNull = new ICmpInst(*UnwindHandler, ICmpInst::ICMP_NE, BufPtr,
- Constant::getNullValue(BufPtr->getType()),
- "notnull");
- BranchInst::Create(UnwindBlock, TermBlock, NotNull, UnwindHandler);
-
- // Create the block to do the longjmp.
- // Get a pointer to the jmpbuf and longjmp.
- Value *Idx[] = { Constant::getNullValue(Type::getInt32Ty(F.getContext())),
- ConstantInt::get(Type::getInt32Ty(F.getContext()), 0) };
- Idx[0] = GetElementPtrInst::Create(BufPtr, Idx, "JmpBuf", UnwindBlock);
- Idx[0] = new BitCastInst(Idx[0],
- Type::getInt8PtrTy(F.getContext()),
- "tmp", UnwindBlock);
- Idx[1] = ConstantInt::get(Type::getInt32Ty(F.getContext()), 1);
- CallInst::Create(LongJmpFn, Idx, "", UnwindBlock);
- new UnreachableInst(F.getContext(), UnwindBlock);
-
- // Set up the term block ("throw without a catch").
- new UnreachableInst(F.getContext(), TermBlock);
-
- // Insert a call to abort()
- CallInst::Create(AbortFn, "",
- TermBlock->getTerminator())->setTailCall();
-
- // Replace the inserted unreachable with a branch to the unwind handler.
- if (UnreachablePlaceholder) {
- BranchInst::Create(UnwindHandler, UnreachablePlaceholder);
- UnreachablePlaceholder->eraseFromParent();
- }
-
- // Finally, for any returns from this function, if this function contains an
- // invoke, restore the old jmpbuf pointer to its input value.
- if (OldJmpBufPtr) {
- for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
- ReturnInst *R = Returns[i];
-
- // Before the return, insert a copy from the saved value to the new value.
- Value *OldBuf = new LoadInst(OldJmpBufPtr, "oldjmpbufptr", true, R);
- new StoreInst(OldBuf, JBListHead, true, R);
- }
- }
-
- return true;
-}
-
-bool LowerInvoke::runOnFunction(Function &F) {
- TargetTransformInfo *TTI = getAnalysisIfAvailable<TargetTransformInfo>();
- if (TTI)
- STTI = TTI->getScalarTargetTransformInfo();
-
- if (useExpensiveEHSupport)
- return insertExpensiveEHSupport(F);
- else
- return insertCheapEHSupport(F);
-}