// Traverse the DFG and collect the set dead RefNodes and the set of
// dead instructions. Return "true" if any of these sets is non-empty,
// "false" otherwise.
bool DeadCodeElimination::collect() {
// This function works by first finding all live nodes. The dead nodes
// are then the complement of the set of live nodes.
//
// Assume that all nodes are dead. Identify instructions which must be
// considered live, i.e. instructions with observable side-effects, such
// as calls and stores. All arguments of such instructions are considered
// live. For each live def, all operands used in the corresponding
// instruction are considered live. For each live use, all its reaching
// defs are considered live.
LiveNodes.clear();
SetVector<NodeId> WorkQ;
for (NodeAddr<BlockNode*> BA : DFG.getFunc().Addr->members(DFG))
for (NodeAddr<InstrNode*> IA : BA.Addr->members(DFG))
scanInstr(IA, WorkQ);
while (!WorkQ.empty()) {
NodeId N = *WorkQ.begin();
WorkQ.remove(N);
LiveNodes.insert(N);
auto RA = DFG.addr<RefNode*>(N);
if (DFG.IsDef(RA))
processDef(RA, WorkQ);
else
processUse(RA, WorkQ);
}
if (trace()) {
dbgs() << "Live nodes:\n";
for (NodeId N : LiveNodes) {
auto RA = DFG.addr<RefNode*>(N);
dbgs() << PrintNode<RefNode*>(RA, DFG) << "\n";
}
}
auto IsDead = [this] (NodeAddr<InstrNode*> IA) -> bool {
for (NodeAddr<DefNode*> DA : IA.Addr->members_if(DFG.IsDef, DFG))
if (LiveNodes.count(DA.Id))
return false;
return true;
};
for (NodeAddr<BlockNode*> BA : DFG.getFunc().Addr->members(DFG)) {
for (NodeAddr<InstrNode*> IA : BA.Addr->members(DFG)) {
for (NodeAddr<RefNode*> RA : IA.Addr->members(DFG))
if (!LiveNodes.count(RA.Id))
DeadNodes.insert(RA.Id);
if (DFG.IsCode<NodeAttrs::Stmt>(IA))
if (isLiveInstr(NodeAddr<StmtNode*>(IA).Addr->getCode()))
continue;
if (IsDead(IA)) {
DeadInstrs.insert(IA.Id);
if (trace())
dbgs() << "Dead instr: " << PrintNode<InstrNode*>(IA, DFG) << "\n";
}
}
}
return !DeadNodes.empty();
}
void GCPtrTracker::recalculateBBsStates() {
SetVector<const BasicBlock *> Worklist;
// TODO: This order is suboptimal, it's better to replace it with priority
// queue where priority is RPO number of BB.
for (auto &BBI : BlockMap)
Worklist.insert(BBI.first);
// This loop iterates the AvailableIn/Out sets until it converges.
// The AvailableIn and AvailableOut sets decrease as we iterate.
while (!Worklist.empty()) {
const BasicBlock *BB = Worklist.pop_back_val();
BasicBlockState *BBS = BlockMap[BB];
size_t OldInCount = BBS->AvailableIn.size();
for (const BasicBlock *PBB : predecessors(BB))
set_intersect(BBS->AvailableIn, BlockMap[PBB]->AvailableOut);
assert(OldInCount >= BBS->AvailableIn.size() && "invariant!");
bool InputsChanged = OldInCount != BBS->AvailableIn.size();
bool ContributionChanged =
removeValidUnrelocatedDefs(BB, BBS, BBS->Contribution);
if (!InputsChanged && !ContributionChanged)
continue;
size_t OldOutCount = BBS->AvailableOut.size();
transferBlock(BB, *BBS, ContributionChanged);
if (OldOutCount != BBS->AvailableOut.size()) {
assert(OldOutCount > BBS->AvailableOut.size() && "invariant!");
Worklist.insert(succ_begin(BB), succ_end(BB));
}
}
}
// If a linkonce global is present in the MustPreserveSymbols, we need to make
// sure we honor this. To force the compiler to not drop it, we add it to the
// "llvm.compiler.used" global.
void LTOCodeGenerator::preserveDiscardableGVs(
Module &TheModule,
llvm::function_ref<bool(const GlobalValue &)> mustPreserveGV) {
SetVector<Constant *> UsedValuesSet;
if (GlobalVariable *LLVMUsed =
TheModule.getGlobalVariable("llvm.compiler.used")) {
ConstantArray *Inits = cast<ConstantArray>(LLVMUsed->getInitializer());
for (auto &V : Inits->operands())
UsedValuesSet.insert(cast<Constant>(&V));
LLVMUsed->eraseFromParent();
}
llvm::Type *i8PTy = llvm::Type::getInt8PtrTy(TheModule.getContext());
auto mayPreserveGlobal = [&](GlobalValue &GV) {
if (!GV.isDiscardableIfUnused() || GV.isDeclaration())
return;
if (!mustPreserveGV(GV))
return;
if (GV.hasAvailableExternallyLinkage()) {
emitWarning(
(Twine("Linker asked to preserve available_externally global: '") +
GV.getName() + "'").str());
return;
}
if (GV.hasInternalLinkage()) {
emitWarning((Twine("Linker asked to preserve internal global: '") +
GV.getName() + "'").str());
return;
}
UsedValuesSet.insert(ConstantExpr::getBitCast(&GV, i8PTy));
};
for (auto &GV : TheModule)
mayPreserveGlobal(GV);
for (auto &GV : TheModule.globals())
mayPreserveGlobal(GV);
for (auto &GV : TheModule.aliases())
mayPreserveGlobal(GV);
if (UsedValuesSet.empty())
return;
llvm::ArrayType *ATy = llvm::ArrayType::get(i8PTy, UsedValuesSet.size());
auto *LLVMUsed = new llvm::GlobalVariable(
TheModule, ATy, false, llvm::GlobalValue::AppendingLinkage,
llvm::ConstantArray::get(ATy, UsedValuesSet.getArrayRef()),
"llvm.compiler.used");
LLVMUsed->setSection("llvm.metadata");
}
bool PlaceSafepoints::runOnFunction(Function &F) {
if (F.isDeclaration() || F.empty()) {
// This is a declaration, nothing to do. Must exit early to avoid crash in
// dom tree calculation
return false;
}
if (isGCSafepointPoll(F)) {
// Given we're inlining this inside of safepoint poll insertion, this
// doesn't make any sense. Note that we do make any contained calls
// parseable after we inline a poll.
return false;
}
if (!shouldRewriteFunction(F))
return false;
bool modified = false;
// In various bits below, we rely on the fact that uses are reachable from
// defs. When there are basic blocks unreachable from the entry, dominance
// and reachablity queries return non-sensical results. Thus, we preprocess
// the function to ensure these properties hold.
modified |= removeUnreachableBlocks(F);
// STEP 1 - Insert the safepoint polling locations. We do not need to
// actually insert parse points yet. That will be done for all polls and
// calls in a single pass.
DominatorTree DT;
DT.recalculate(F);
SmallVector<Instruction *, 16> PollsNeeded;
std::vector<CallSite> ParsePointNeeded;
if (enableBackedgeSafepoints(F)) {
// Construct a pass manager to run the LoopPass backedge logic. We
// need the pass manager to handle scheduling all the loop passes
// appropriately. Doing this by hand is painful and just not worth messing
// with for the moment.
legacy::FunctionPassManager FPM(F.getParent());
bool CanAssumeCallSafepoints = enableCallSafepoints(F);
PlaceBackedgeSafepointsImpl *PBS =
new PlaceBackedgeSafepointsImpl(CanAssumeCallSafepoints);
FPM.add(PBS);
FPM.run(F);
// We preserve dominance information when inserting the poll, otherwise
// we'd have to recalculate this on every insert
DT.recalculate(F);
auto &PollLocations = PBS->PollLocations;
auto OrderByBBName = [](Instruction *a, Instruction *b) {
return a->getParent()->getName() < b->getParent()->getName();
};
// We need the order of list to be stable so that naming ends up stable
// when we split edges. This makes test cases much easier to write.
std::sort(PollLocations.begin(), PollLocations.end(), OrderByBBName);
// We can sometimes end up with duplicate poll locations. This happens if
// a single loop is visited more than once. The fact this happens seems
// wrong, but it does happen for the split-backedge.ll test case.
PollLocations.erase(std::unique(PollLocations.begin(),
PollLocations.end()),
PollLocations.end());
// Insert a poll at each point the analysis pass identified
// The poll location must be the terminator of a loop latch block.
for (TerminatorInst *Term : PollLocations) {
// We are inserting a poll, the function is modified
modified = true;
if (SplitBackedge) {
// Split the backedge of the loop and insert the poll within that new
// basic block. This creates a loop with two latches per original
// latch (which is non-ideal), but this appears to be easier to
// optimize in practice than inserting the poll immediately before the
// latch test.
// Since this is a latch, at least one of the successors must dominate
// it. Its possible that we have a) duplicate edges to the same header
// and b) edges to distinct loop headers. We need to insert pools on
// each.
SetVector<BasicBlock *> Headers;
for (unsigned i = 0; i < Term->getNumSuccessors(); i++) {
BasicBlock *Succ = Term->getSuccessor(i);
if (DT.dominates(Succ, Term->getParent())) {
Headers.insert(Succ);
}
}
assert(!Headers.empty() && "poll location is not a loop latch?");
// The split loop structure here is so that we only need to recalculate
// the dominator tree once. Alternatively, we could just keep it up to
// date and use a more natural merged loop.
SetVector<BasicBlock *> SplitBackedges;
for (BasicBlock *Header : Headers) {
BasicBlock *NewBB = SplitEdge(Term->getParent(), Header, &DT);
PollsNeeded.push_back(NewBB->getTerminator());
NumBackedgeSafepoints++;
}
} else {
// Split the latch block itself, right before the terminator.
PollsNeeded.push_back(Term);
NumBackedgeSafepoints++;
}
}
}
if (enableEntrySafepoints(F)) {
Instruction *Location = findLocationForEntrySafepoint(F, DT);
if (!Location) {
// policy choice not to insert?
} else {
PollsNeeded.push_back(Location);
modified = true;
NumEntrySafepoints++;
}
}
// Now that we've identified all the needed safepoint poll locations, insert
// safepoint polls themselves.
for (Instruction *PollLocation : PollsNeeded) {
std::vector<CallSite> RuntimeCalls;
InsertSafepointPoll(PollLocation, RuntimeCalls);
ParsePointNeeded.insert(ParsePointNeeded.end(), RuntimeCalls.begin(),
RuntimeCalls.end());
}
// If we've been asked to not wrap the calls with gc.statepoint, then we're
// done. In the near future, this option will be "constant folded" to true,
// and the code below that deals with insert gc.statepoint calls will be
// removed. Wrapping potentially safepointing calls in gc.statepoint will
// then become the responsibility of the RewriteStatepointsForGC pass.
if (NoStatepoints)
return modified;
PollsNeeded.clear(); // make sure we don't accidentally use
// The dominator tree has been invalidated by the inlining performed in the
// above loop. TODO: Teach the inliner how to update the dom tree?
DT.recalculate(F);
if (enableCallSafepoints(F)) {
std::vector<CallSite> Calls;
findCallSafepoints(F, Calls);
NumCallSafepoints += Calls.size();
ParsePointNeeded.insert(ParsePointNeeded.end(), Calls.begin(), Calls.end());
}
// Unique the vectors since we can end up with duplicates if we scan the call
// site for call safepoints after we add it for entry or backedge. The
// only reason we need tracking at all is that some functions might have
// polls but not call safepoints and thus we might miss marking the runtime
// calls for the polls. (This is useful in test cases!)
unique_unsorted(ParsePointNeeded);
// Any parse point (no matter what source) will be handled here
// We're about to start modifying the function
if (!ParsePointNeeded.empty())
modified = true;
// Now run through and insert the safepoints, but do _NOT_ update or remove
// any existing uses. We have references to live variables that need to
// survive to the last iteration of this loop.
std::vector<Value *> Results;
Results.reserve(ParsePointNeeded.size());
for (size_t i = 0; i < ParsePointNeeded.size(); i++) {
CallSite &CS = ParsePointNeeded[i];
// For invoke statepoints we need to remove all phi nodes at the normal
// destination block.
// Reason for this is that we can place gc_result only after last phi node
// in basic block. We will get malformed code after RAUW for the
// gc_result if one of this phi nodes uses result from the invoke.
if (InvokeInst *Invoke = dyn_cast<InvokeInst>(CS.getInstruction())) {
normalizeForInvokeSafepoint(Invoke->getNormalDest(),
Invoke->getParent());
}
Value *GCResult = ReplaceWithStatepoint(CS);
Results.push_back(GCResult);
}
assert(Results.size() == ParsePointNeeded.size());
// Adjust all users of the old call sites to use the new ones instead
for (size_t i = 0; i < ParsePointNeeded.size(); i++) {
CallSite &CS = ParsePointNeeded[i];
Value *GCResult = Results[i];
if (GCResult) {
// Can not RAUW for the invoke gc result in case of phi nodes preset.
assert(CS.isCall() || !isa<PHINode>(cast<Instruction>(GCResult)->getParent()->begin()));
// Replace all uses with the new call
CS.getInstruction()->replaceAllUsesWith(GCResult);
}
// Now that we've handled all uses, remove the original call itself
// Note: The insert point can't be the deleted instruction!
CS.getInstruction()->eraseFromParent();
}
return modified;
}
bool PlaceSafepoints::runOnFunction(Function &F) {
if (F.isDeclaration() || F.empty()) {
// This is a declaration, nothing to do. Must exit early to avoid crash in
// dom tree calculation
return false;
}
if (isGCSafepointPoll(F)) {
// Given we're inlining this inside of safepoint poll insertion, this
// doesn't make any sense. Note that we do make any contained calls
// parseable after we inline a poll.
return false;
}
if (!shouldRewriteFunction(F))
return false;
const TargetLibraryInfo &TLI =
getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
bool Modified = false;
// In various bits below, we rely on the fact that uses are reachable from
// defs. When there are basic blocks unreachable from the entry, dominance
// and reachablity queries return non-sensical results. Thus, we preprocess
// the function to ensure these properties hold.
Modified |= removeUnreachableBlocks(F);
// STEP 1 - Insert the safepoint polling locations. We do not need to
// actually insert parse points yet. That will be done for all polls and
// calls in a single pass.
DominatorTree DT;
DT.recalculate(F);
SmallVector<Instruction *, 16> PollsNeeded;
std::vector<CallSite> ParsePointNeeded;
if (enableBackedgeSafepoints(F)) {
// Construct a pass manager to run the LoopPass backedge logic. We
// need the pass manager to handle scheduling all the loop passes
// appropriately. Doing this by hand is painful and just not worth messing
// with for the moment.
legacy::FunctionPassManager FPM(F.getParent());
bool CanAssumeCallSafepoints = enableCallSafepoints(F);
auto *PBS = new PlaceBackedgeSafepointsImpl(CanAssumeCallSafepoints);
FPM.add(PBS);
FPM.run(F);
// We preserve dominance information when inserting the poll, otherwise
// we'd have to recalculate this on every insert
DT.recalculate(F);
auto &PollLocations = PBS->PollLocations;
auto OrderByBBName = [](Instruction *a, Instruction *b) {
return a->getParent()->getName() < b->getParent()->getName();
};
// We need the order of list to be stable so that naming ends up stable
// when we split edges. This makes test cases much easier to write.
llvm::sort(PollLocations.begin(), PollLocations.end(), OrderByBBName);
// We can sometimes end up with duplicate poll locations. This happens if
// a single loop is visited more than once. The fact this happens seems
// wrong, but it does happen for the split-backedge.ll test case.
PollLocations.erase(std::unique(PollLocations.begin(),
PollLocations.end()),
PollLocations.end());
// Insert a poll at each point the analysis pass identified
// The poll location must be the terminator of a loop latch block.
for (TerminatorInst *Term : PollLocations) {
// We are inserting a poll, the function is modified
Modified = true;
if (SplitBackedge) {
// Split the backedge of the loop and insert the poll within that new
// basic block. This creates a loop with two latches per original
// latch (which is non-ideal), but this appears to be easier to
// optimize in practice than inserting the poll immediately before the
// latch test.
// Since this is a latch, at least one of the successors must dominate
// it. Its possible that we have a) duplicate edges to the same header
// and b) edges to distinct loop headers. We need to insert pools on
// each.
SetVector<BasicBlock *> Headers;
for (unsigned i = 0; i < Term->getNumSuccessors(); i++) {
BasicBlock *Succ = Term->getSuccessor(i);
if (DT.dominates(Succ, Term->getParent())) {
Headers.insert(Succ);
}
}
assert(!Headers.empty() && "poll location is not a loop latch?");
// The split loop structure here is so that we only need to recalculate
// the dominator tree once. Alternatively, we could just keep it up to
// date and use a more natural merged loop.
SetVector<BasicBlock *> SplitBackedges;
for (BasicBlock *Header : Headers) {
BasicBlock *NewBB = SplitEdge(Term->getParent(), Header, &DT);
PollsNeeded.push_back(NewBB->getTerminator());
NumBackedgeSafepoints++;
}
} else {
// Split the latch block itself, right before the terminator.
PollsNeeded.push_back(Term);
NumBackedgeSafepoints++;
}
}
}
if (enableEntrySafepoints(F)) {
if (Instruction *Location = findLocationForEntrySafepoint(F, DT)) {
PollsNeeded.push_back(Location);
Modified = true;
NumEntrySafepoints++;
}
// TODO: else we should assert that there was, in fact, a policy choice to
// not insert a entry safepoint poll.
}
// Now that we've identified all the needed safepoint poll locations, insert
// safepoint polls themselves.
for (Instruction *PollLocation : PollsNeeded) {
std::vector<CallSite> RuntimeCalls;
InsertSafepointPoll(PollLocation, RuntimeCalls, TLI);
ParsePointNeeded.insert(ParsePointNeeded.end(), RuntimeCalls.begin(),
RuntimeCalls.end());
}
return Modified;
}
// Erase the nodes given in the Nodes set from DFG. In addition to removing
// them from the DFG, if a node corresponds to a statement, the corresponding
// machine instruction is erased from the function.
bool DeadCodeElimination::erase(const SetVector<NodeId> &Nodes) {
if (Nodes.empty())
return false;
// Prepare the actual set of ref nodes to remove: ref nodes from Nodes
// are included directly, for each InstrNode in Nodes, include the set
// of all RefNodes from it.
NodeList DRNs, DINs;
for (auto I : Nodes) {
auto BA = DFG.addr<NodeBase*>(I);
uint16_t Type = BA.Addr->getType();
if (Type == NodeAttrs::Ref) {
DRNs.push_back(DFG.addr<RefNode*>(I));
continue;
}
// If it's a code node, add all ref nodes from it.
uint16_t Kind = BA.Addr->getKind();
if (Kind == NodeAttrs::Stmt || Kind == NodeAttrs::Phi) {
for (auto N : NodeAddr<CodeNode*>(BA).Addr->members(DFG))
DRNs.push_back(N);
DINs.push_back(DFG.addr<InstrNode*>(I));
} else {
llvm_unreachable("Unexpected code node");
return false;
}
}
// Sort the list so that use nodes are removed first. This makes the
// "unlink" functions a bit faster.
auto UsesFirst = [] (NodeAddr<RefNode*> A, NodeAddr<RefNode*> B) -> bool {
uint16_t KindA = A.Addr->getKind(), KindB = B.Addr->getKind();
if (KindA == NodeAttrs::Use && KindB == NodeAttrs::Def)
return true;
if (KindA == NodeAttrs::Def && KindB == NodeAttrs::Use)
return false;
return A.Id < B.Id;
};
llvm::sort(DRNs, UsesFirst);
if (trace())
dbgs() << "Removing dead ref nodes:\n";
for (NodeAddr<RefNode*> RA : DRNs) {
if (trace())
dbgs() << " " << PrintNode<RefNode*>(RA, DFG) << '\n';
if (DFG.IsUse(RA))
DFG.unlinkUse(RA, true);
else if (DFG.IsDef(RA))
DFG.unlinkDef(RA, true);
}
// Now, remove all dead instruction nodes.
for (NodeAddr<InstrNode*> IA : DINs) {
NodeAddr<BlockNode*> BA = IA.Addr->getOwner(DFG);
BA.Addr->removeMember(IA, DFG);
if (!DFG.IsCode<NodeAttrs::Stmt>(IA))
continue;
MachineInstr *MI = NodeAddr<StmtNode*>(IA).Addr->getCode();
if (trace())
dbgs() << "erasing: " << *MI;
MI->eraseFromParent();
}
return true;
}
bool WebAssemblyFixIrreducibleControlFlow::VisitLoop(MachineFunction &MF,
MachineLoopInfo &MLI,
MachineLoop *Loop) {
MachineBasicBlock *Header = Loop ? Loop->getHeader() : &*MF.begin();
SetVector<MachineBasicBlock *> RewriteSuccs;
// DFS through Loop's body, looking for for irreducible control flow. Loop is
// natural, and we stay in its body, and we treat any nested loops
// monolithically, so any cycles we encounter indicate irreducibility.
SmallPtrSet<MachineBasicBlock *, 8> OnStack;
SmallPtrSet<MachineBasicBlock *, 8> Visited;
SmallVector<SuccessorList, 4> LoopWorklist;
LoopWorklist.push_back(SuccessorList(Header));
OnStack.insert(Header);
Visited.insert(Header);
while (!LoopWorklist.empty()) {
SuccessorList &Top = LoopWorklist.back();
if (Top.HasNext()) {
MachineBasicBlock *Next = Top.Next();
if (Next == Header || (Loop && !Loop->contains(Next)))
continue;
if (LLVM_LIKELY(OnStack.insert(Next).second)) {
if (!Visited.insert(Next).second) {
OnStack.erase(Next);
continue;
}
MachineLoop *InnerLoop = MLI.getLoopFor(Next);
if (InnerLoop != Loop)
LoopWorklist.push_back(SuccessorList(InnerLoop));
else
LoopWorklist.push_back(SuccessorList(Next));
} else {
RewriteSuccs.insert(Top.getBlock());
}
continue;
}
OnStack.erase(Top.getBlock());
LoopWorklist.pop_back();
}
// Most likely, we didn't find any irreducible control flow.
if (LLVM_LIKELY(RewriteSuccs.empty()))
return false;
DEBUG(dbgs() << "Irreducible control flow detected!\n");
// Ok. We have irreducible control flow! Create a dispatch block which will
// contains a jump table to any block in the problematic set of blocks.
MachineBasicBlock *Dispatch = MF.CreateMachineBasicBlock();
MF.insert(MF.end(), Dispatch);
MLI.changeLoopFor(Dispatch, Loop);
// Add the jump table.
const auto &TII = *MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo();
MachineInstrBuilder MIB = BuildMI(*Dispatch, Dispatch->end(), DebugLoc(),
TII.get(WebAssembly::BR_TABLE_I32));
// Add the register which will be used to tell the jump table which block to
// jump to.
MachineRegisterInfo &MRI = MF.getRegInfo();
unsigned Reg = MRI.createVirtualRegister(&WebAssembly::I32RegClass);
MIB.addReg(Reg);
// Collect all the blocks which need to have their successors rewritten,
// add the successors to the jump table, and remember their index.
DenseMap<MachineBasicBlock *, unsigned> Indices;
SmallVector<MachineBasicBlock *, 4> SuccWorklist(RewriteSuccs.begin(),
RewriteSuccs.end());
while (!SuccWorklist.empty()) {
MachineBasicBlock *MBB = SuccWorklist.pop_back_val();
auto Pair = Indices.insert(std::make_pair(MBB, 0));
if (!Pair.second)
continue;
unsigned Index = MIB.getInstr()->getNumExplicitOperands() - 1;
DEBUG(dbgs() << printMBBReference(*MBB) << " has index " << Index << "\n");
Pair.first->second = Index;
for (auto Pred : MBB->predecessors())
RewriteSuccs.insert(Pred);
MIB.addMBB(MBB);
Dispatch->addSuccessor(MBB);
MetaBlock Meta(MBB);
for (auto *Succ : Meta.successors())
if (Succ != Header && (!Loop || Loop->contains(Succ)))
SuccWorklist.push_back(Succ);
}
// Rewrite the problematic successors for every block in RewriteSuccs.
// For simplicity, we just introduce a new block for every edge we need to
// rewrite. Fancier things are possible.
for (MachineBasicBlock *MBB : RewriteSuccs) {
DenseMap<MachineBasicBlock *, MachineBasicBlock *> Map;
for (auto *Succ : MBB->successors()) {
if (!Indices.count(Succ))
continue;
MachineBasicBlock *Split = MF.CreateMachineBasicBlock();
MF.insert(MBB->isLayoutSuccessor(Succ) ? MachineFunction::iterator(Succ)
: MF.end(),
Split);
MLI.changeLoopFor(Split, Loop);
// Set the jump table's register of the index of the block we wish to
// jump to, and jump to the jump table.
BuildMI(*Split, Split->end(), DebugLoc(), TII.get(WebAssembly::CONST_I32),
Reg)
.addImm(Indices[Succ]);
BuildMI(*Split, Split->end(), DebugLoc(), TII.get(WebAssembly::BR))
.addMBB(Dispatch);
Split->addSuccessor(Dispatch);
Map[Succ] = Split;
}
// Remap the terminator operands and the successor list.
for (MachineInstr &Term : MBB->terminators())
for (auto &Op : Term.explicit_uses())
if (Op.isMBB() && Indices.count(Op.getMBB()))
Op.setMBB(Map[Op.getMBB()]);
for (auto Rewrite : Map)
MBB->replaceSuccessor(Rewrite.first, Rewrite.second);
}
// Create a fake default label, because br_table requires one.
MIB.addMBB(MIB.getInstr()
->getOperand(MIB.getInstr()->getNumExplicitOperands() - 1)
.getMBB());
return true;
}
