/// RewriteUsesOfClonedInstructions - We just cloned the instructions from the
/// old header into the preheader. If there were uses of the values produced by
/// these instruction that were outside of the loop, we have to insert PHI nodes
/// to merge the two values. Do this now.
static void RewriteUsesOfClonedInstructions(BasicBlock *OrigHeader,
BasicBlock *OrigPreheader,
ValueToValueMapTy &ValueMap) {
// Remove PHI node entries that are no longer live.
BasicBlock::iterator I, E = OrigHeader->end();
for (I = OrigHeader->begin(); PHINode *PN = dyn_cast<PHINode>(I); ++I)
PN->removeIncomingValue(PN->getBasicBlockIndex(OrigPreheader));
// Now fix up users of the instructions in OrigHeader, inserting PHI nodes
// as necessary.
SSAUpdater SSA;
for (I = OrigHeader->begin(); I != E; ++I) {
Value *OrigHeaderVal = I;
// If there are no uses of the value (e.g. because it returns void), there
// is nothing to rewrite.
if (OrigHeaderVal->use_empty())
continue;
Value *OrigPreHeaderVal = ValueMap[OrigHeaderVal];
// The value now exits in two versions: the initial value in the preheader
// and the loop "next" value in the original header.
SSA.Initialize(OrigHeaderVal->getType(), OrigHeaderVal->getName());
SSA.AddAvailableValue(OrigHeader, OrigHeaderVal);
SSA.AddAvailableValue(OrigPreheader, OrigPreHeaderVal);
// Visit each use of the OrigHeader instruction.
for (Value::use_iterator UI = OrigHeaderVal->use_begin(),
UE = OrigHeaderVal->use_end(); UI != UE; ) {
// Grab the use before incrementing the iterator.
Use &U = *UI;
// Increment the iterator before removing the use from the list.
++UI;
// SSAUpdater can't handle a non-PHI use in the same block as an
// earlier def. We can easily handle those cases manually.
Instruction *UserInst = cast<Instruction>(U.getUser());
if (!isa<PHINode>(UserInst)) {
BasicBlock *UserBB = UserInst->getParent();
// The original users in the OrigHeader are already using the
// original definitions.
if (UserBB == OrigHeader)
continue;
// Users in the OrigPreHeader need to use the value to which the
// original definitions are mapped.
if (UserBB == OrigPreheader) {
U = OrigPreHeaderVal;
continue;
}
}
// Anything else can be handled by SSAUpdater.
SSA.RewriteUse(U);
}
}
}
void BBCloner::UpdateSSA(Function &F) {
DominatorTree &DT = getAnalysis<DominatorTree>();
// The function has been greatly modified since the beginning.
DT.runOnFunction(F);
vector<pair<Instruction *, Use *> > ToResolve;
for (ValueToValueMapTy::iterator I = CloneMap.begin();
I != CloneMap.end();
++I) {
Value *Key = const_cast<Value *>(I->first);
if (Instruction *OldIns = dyn_cast<Instruction>(Key)) {
for (Value::use_iterator UI = OldIns->use_begin();
UI != OldIns->use_end();
++UI) {
if (Instruction *User = dyn_cast<Instruction>(*UI)) {
if (!DT.dominates(OldIns, User))
ToResolve.push_back(make_pair(OldIns, &UI.getUse()));
}
}
Instruction *NewIns = cast<Instruction>(I->second);
for (Value::use_iterator UI = NewIns->use_begin();
UI != NewIns->use_end();
++UI) {
if (Instruction *User = dyn_cast<Instruction>(*UI)) {
if (!DT.dominates(NewIns, User)) {
// Use OldIns intentionally.
ToResolve.push_back(make_pair(OldIns, &UI.getUse()));
}
}
}
}
}
for (size_t i = 0; i < ToResolve.size(); ) {
Instruction *OldIns = ToResolve[i].first;
Instruction *NewIns = cast<Instruction>(CloneMap.lookup(OldIns));
SSAUpdater SU;
SU.Initialize(OldIns->getType(), OldIns->getName());
SU.AddAvailableValue(OldIns->getParent(), OldIns);
SU.AddAvailableValue(NewIns->getParent(), NewIns);
size_t j = i;
while (j < ToResolve.size() && ToResolve[j].first == ToResolve[i].first) {
SU.RewriteUse(*ToResolve[j].second);
++j;
}
i = j;
}
}
/// ProcessInstruction - Given an instruction in the loop, check to see if it
/// has any uses that are outside the current loop. If so, insert LCSSA PHI
/// nodes and rewrite the uses.
bool LCSSA::ProcessInstruction(Instruction *Inst,
const SmallVectorImpl<BasicBlock*> &ExitBlocks) {
SmallVector<Use*, 16> UsesToRewrite;
BasicBlock *InstBB = Inst->getParent();
for (Value::use_iterator UI = Inst->use_begin(), E = Inst->use_end();
UI != E; ++UI) {
User *U = *UI;
BasicBlock *UserBB = cast<Instruction>(U)->getParent();
if (PHINode *PN = dyn_cast<PHINode>(U))
UserBB = PN->getIncomingBlock(UI);
if (InstBB != UserBB && !inLoop(UserBB))
UsesToRewrite.push_back(&UI.getUse());
}
// If there are no uses outside the loop, exit with no change.
if (UsesToRewrite.empty()) return false;
++NumLCSSA; // We are applying the transformation
// Invoke instructions are special in that their result value is not available
// along their unwind edge. The code below tests to see whether DomBB dominates
// the value, so adjust DomBB to the normal destination block, which is
// effectively where the value is first usable.
BasicBlock *DomBB = Inst->getParent();
if (InvokeInst *Inv = dyn_cast<InvokeInst>(Inst))
DomBB = Inv->getNormalDest();
DomTreeNode *DomNode = DT->getNode(DomBB);
SSAUpdater SSAUpdate;
SSAUpdate.Initialize(Inst->getType(), Inst->getName());
// Insert the LCSSA phi's into all of the exit blocks dominated by the
// value, and add them to the Phi's map.
for (SmallVectorImpl<BasicBlock*>::const_iterator BBI = ExitBlocks.begin(),
BBE = ExitBlocks.end(); BBI != BBE; ++BBI) {
BasicBlock *ExitBB = *BBI;
if (!DT->dominates(DomNode, DT->getNode(ExitBB))) continue;
// If we already inserted something for this BB, don't reprocess it.
if (SSAUpdate.HasValueForBlock(ExitBB)) continue;
PHINode *PN = PHINode::Create(Inst->getType(), Inst->getName()+".lcssa",
ExitBB->begin());
PN->reserveOperandSpace(PredCache.GetNumPreds(ExitBB));
// Add inputs from inside the loop for this PHI.
for (BasicBlock **PI = PredCache.GetPreds(ExitBB); *PI; ++PI) {
PN->addIncoming(Inst, *PI);
// If the exit block has a predecessor not within the loop, arrange for
// the incoming value use corresponding to that predecessor to be
// rewritten in terms of a different LCSSA PHI.
if (!inLoop(*PI))
UsesToRewrite.push_back(
&PN->getOperandUse(
PN->getOperandNumForIncomingValue(PN->getNumIncomingValues()-1)));
}
// Remember that this phi makes the value alive in this block.
SSAUpdate.AddAvailableValue(ExitBB, PN);
}
// Rewrite all uses outside the loop in terms of the new PHIs we just
// inserted.
for (unsigned i = 0, e = UsesToRewrite.size(); i != e; ++i) {
// If this use is in an exit block, rewrite to use the newly inserted PHI.
// This is required for correctness because SSAUpdate doesn't handle uses in
// the same block. It assumes the PHI we inserted is at the end of the
// block.
Instruction *User = cast<Instruction>(UsesToRewrite[i]->getUser());
BasicBlock *UserBB = User->getParent();
if (PHINode *PN = dyn_cast<PHINode>(User))
UserBB = PN->getIncomingBlock(*UsesToRewrite[i]);
if (isa<PHINode>(UserBB->begin()) &&
isExitBlock(UserBB, ExitBlocks)) {
UsesToRewrite[i]->set(UserBB->begin());
continue;
}
// Otherwise, do full PHI insertion.
SSAUpdate.RewriteUse(*UsesToRewrite[i]);
}
return true;
}
/// RewriteUsesOfClonedInstructions - We just cloned the instructions from the
/// old header into the preheader. If there were uses of the values produced by
/// these instruction that were outside of the loop, we have to insert PHI nodes
/// to merge the two values. Do this now.
static void RewriteUsesOfClonedInstructions(BasicBlock *OrigHeader,
BasicBlock *OrigPreheader,
ValueToValueMapTy &ValueMap) {
// Remove PHI node entries that are no longer live.
BasicBlock::iterator I, E = OrigHeader->end();
for (I = OrigHeader->begin(); PHINode *PN = dyn_cast<PHINode>(I); ++I)
PN->removeIncomingValue(PN->getBasicBlockIndex(OrigPreheader));
// Now fix up users of the instructions in OrigHeader, inserting PHI nodes
// as necessary.
SSAUpdater SSA;
for (I = OrigHeader->begin(); I != E; ++I) {
Value *OrigHeaderVal = &*I;
// If there are no uses of the value (e.g. because it returns void), there
// is nothing to rewrite.
if (OrigHeaderVal->use_empty())
continue;
Value *OrigPreHeaderVal = ValueMap.lookup(OrigHeaderVal);
// The value now exits in two versions: the initial value in the preheader
// and the loop "next" value in the original header.
SSA.Initialize(OrigHeaderVal->getType(), OrigHeaderVal->getName());
SSA.AddAvailableValue(OrigHeader, OrigHeaderVal);
SSA.AddAvailableValue(OrigPreheader, OrigPreHeaderVal);
// Visit each use of the OrigHeader instruction.
for (Value::use_iterator UI = OrigHeaderVal->use_begin(),
UE = OrigHeaderVal->use_end(); UI != UE; ) {
// Grab the use before incrementing the iterator.
Use &U = *UI;
// Increment the iterator before removing the use from the list.
++UI;
// SSAUpdater can't handle a non-PHI use in the same block as an
// earlier def. We can easily handle those cases manually.
Instruction *UserInst = cast<Instruction>(U.getUser());
if (!isa<PHINode>(UserInst)) {
BasicBlock *UserBB = UserInst->getParent();
// The original users in the OrigHeader are already using the
// original definitions.
if (UserBB == OrigHeader)
continue;
// Users in the OrigPreHeader need to use the value to which the
// original definitions are mapped.
if (UserBB == OrigPreheader) {
U = OrigPreHeaderVal;
continue;
}
}
// Anything else can be handled by SSAUpdater.
SSA.RewriteUse(U);
}
// Replace MetadataAsValue(ValueAsMetadata(OrigHeaderVal)) uses in debug
// intrinsics.
LLVMContext &C = OrigHeader->getContext();
if (auto *VAM = ValueAsMetadata::getIfExists(OrigHeaderVal)) {
if (auto *MAV = MetadataAsValue::getIfExists(C, VAM)) {
for (auto UI = MAV->use_begin(), E = MAV->use_end(); UI != E; ) {
// Grab the use before incrementing the iterator. Otherwise, altering
// the Use will invalidate the iterator.
Use &U = *UI++;
DbgInfoIntrinsic *UserInst = dyn_cast<DbgInfoIntrinsic>(U.getUser());
if (!UserInst) continue;
// The original users in the OrigHeader are already using the original
// definitions.
BasicBlock *UserBB = UserInst->getParent();
if (UserBB == OrigHeader)
continue;
// Users in the OrigPreHeader need to use the value to which the
// original definitions are mapped and anything else can be handled by
// the SSAUpdater. To avoid adding PHINodes, check if the value is
// available in UserBB, if not substitute undef.
Value *NewVal;
if (UserBB == OrigPreheader)
NewVal = OrigPreHeaderVal;
else if (SSA.HasValueForBlock(UserBB))
NewVal = SSA.GetValueInMiddleOfBlock(UserBB);
else
NewVal = UndefValue::get(OrigHeaderVal->getType());
U = MetadataAsValue::get(C, ValueAsMetadata::get(NewVal));
}
}
}
}
}
bool WebAssemblyLowerEmscriptenEHSjLj::runSjLjOnFunction(Function &F) {
Module &M = *F.getParent();
LLVMContext &C = F.getContext();
IRBuilder<> IRB(C);
SmallVector<Instruction *, 64> ToErase;
// Vector of %setjmpTable values
std::vector<Instruction *> SetjmpTableInsts;
// Vector of %setjmpTableSize values
std::vector<Instruction *> SetjmpTableSizeInsts;
// Setjmp preparation
// This instruction effectively means %setjmpTableSize = 4.
// We create this as an instruction intentionally, and we don't want to fold
// this instruction to a constant 4, because this value will be used in
// SSAUpdater.AddAvailableValue(...) later.
BasicBlock &EntryBB = F.getEntryBlock();
BinaryOperator *SetjmpTableSize = BinaryOperator::Create(
Instruction::Add, IRB.getInt32(4), IRB.getInt32(0), "setjmpTableSize",
&*EntryBB.getFirstInsertionPt());
// setjmpTable = (int *) malloc(40);
Instruction *SetjmpTable = CallInst::CreateMalloc(
SetjmpTableSize, IRB.getInt32Ty(), IRB.getInt32Ty(), IRB.getInt32(40),
nullptr, nullptr, "setjmpTable");
// setjmpTable[0] = 0;
IRB.SetInsertPoint(SetjmpTableSize);
IRB.CreateStore(IRB.getInt32(0), SetjmpTable);
SetjmpTableInsts.push_back(SetjmpTable);
SetjmpTableSizeInsts.push_back(SetjmpTableSize);
// Setjmp transformation
std::vector<PHINode *> SetjmpRetPHIs;
Function *SetjmpF = M.getFunction("setjmp");
for (User *U : SetjmpF->users()) {
auto *CI = dyn_cast<CallInst>(U);
if (!CI)
report_fatal_error("Does not support indirect calls to setjmp");
BasicBlock *BB = CI->getParent();
if (BB->getParent() != &F) // in other function
continue;
// The tail is everything right after the call, and will be reached once
// when setjmp is called, and later when longjmp returns to the setjmp
BasicBlock *Tail = SplitBlock(BB, CI->getNextNode());
// Add a phi to the tail, which will be the output of setjmp, which
// indicates if this is the first call or a longjmp back. The phi directly
// uses the right value based on where we arrive from
IRB.SetInsertPoint(Tail->getFirstNonPHI());
PHINode *SetjmpRet = IRB.CreatePHI(IRB.getInt32Ty(), 2, "setjmp.ret");
// setjmp initial call returns 0
SetjmpRet->addIncoming(IRB.getInt32(0), BB);
// The proper output is now this, not the setjmp call itself
CI->replaceAllUsesWith(SetjmpRet);
// longjmp returns to the setjmp will add themselves to this phi
SetjmpRetPHIs.push_back(SetjmpRet);
// Fix call target
// Our index in the function is our place in the array + 1 to avoid index
// 0, because index 0 means the longjmp is not ours to handle.
IRB.SetInsertPoint(CI);
Value *Args[] = {CI->getArgOperand(0), IRB.getInt32(SetjmpRetPHIs.size()),
SetjmpTable, SetjmpTableSize};
Instruction *NewSetjmpTable =
IRB.CreateCall(SaveSetjmpF, Args, "setjmpTable");
Instruction *NewSetjmpTableSize =
IRB.CreateLoad(TempRet0GV, "setjmpTableSize");
SetjmpTableInsts.push_back(NewSetjmpTable);
SetjmpTableSizeInsts.push_back(NewSetjmpTableSize);
ToErase.push_back(CI);
}
// Update each call that can longjmp so it can return to a setjmp where
// relevant.
// Because we are creating new BBs while processing and don't want to make
// all these newly created BBs candidates again for longjmp processing, we
// first make the vector of candidate BBs.
std::vector<BasicBlock *> BBs;
for (BasicBlock &BB : F)
BBs.push_back(&BB);
// BBs.size() will change within the loop, so we query it every time
for (unsigned i = 0; i < BBs.size(); i++) {
BasicBlock *BB = BBs[i];
for (Instruction &I : *BB) {
assert(!isa<InvokeInst>(&I));
auto *CI = dyn_cast<CallInst>(&I);
if (!CI)
continue;
const Value *Callee = CI->getCalledValue();
if (!canLongjmp(M, Callee))
continue;
Value *Threw = nullptr;
BasicBlock *Tail;
if (Callee->getName().startswith(InvokePrefix)) {
// If invoke wrapper has already been generated for this call in
// previous EH phase, search for the load instruction
// %__THREW__.val = __THREW__;
// in postamble after the invoke wrapper call
LoadInst *ThrewLI = nullptr;
StoreInst *ThrewResetSI = nullptr;
for (auto I = std::next(BasicBlock::iterator(CI)), IE = BB->end();
I != IE; ++I) {
if (auto *LI = dyn_cast<LoadInst>(I))
if (auto *GV = dyn_cast<GlobalVariable>(LI->getPointerOperand()))
if (GV == ThrewGV) {
Threw = ThrewLI = LI;
break;
}
}
// Search for the store instruction after the load above
// __THREW__ = 0;
for (auto I = std::next(BasicBlock::iterator(ThrewLI)), IE = BB->end();
I != IE; ++I) {
if (auto *SI = dyn_cast<StoreInst>(I))
if (auto *GV = dyn_cast<GlobalVariable>(SI->getPointerOperand()))
if (GV == ThrewGV && SI->getValueOperand() == IRB.getInt32(0)) {
ThrewResetSI = SI;
break;
}
}
assert(Threw && ThrewLI && "Cannot find __THREW__ load after invoke");
assert(ThrewResetSI && "Cannot find __THREW__ store after invoke");
Tail = SplitBlock(BB, ThrewResetSI->getNextNode());
} else {
// Wrap call with invoke wrapper and generate preamble/postamble
Threw = wrapInvoke(CI);
ToErase.push_back(CI);
Tail = SplitBlock(BB, CI->getNextNode());
}
// We need to replace the terminator in Tail - SplitBlock makes BB go
// straight to Tail, we need to check if a longjmp occurred, and go to the
// right setjmp-tail if so
ToErase.push_back(BB->getTerminator());
// Generate a function call to testSetjmp function and preamble/postamble
// code to figure out (1) whether longjmp occurred (2) if longjmp
// occurred, which setjmp it corresponds to
Value *Label = nullptr;
Value *LongjmpResult = nullptr;
BasicBlock *EndBB = nullptr;
wrapTestSetjmp(BB, CI, Threw, SetjmpTable, SetjmpTableSize, Label,
LongjmpResult, EndBB);
assert(Label && LongjmpResult && EndBB);
// Create switch instruction
IRB.SetInsertPoint(EndBB);
SwitchInst *SI = IRB.CreateSwitch(Label, Tail, SetjmpRetPHIs.size());
// -1 means no longjmp happened, continue normally (will hit the default
// switch case). 0 means a longjmp that is not ours to handle, needs a
// rethrow. Otherwise the index is the same as the index in P+1 (to avoid
// 0).
for (unsigned i = 0; i < SetjmpRetPHIs.size(); i++) {
SI->addCase(IRB.getInt32(i + 1), SetjmpRetPHIs[i]->getParent());
SetjmpRetPHIs[i]->addIncoming(LongjmpResult, EndBB);
}
// We are splitting the block here, and must continue to find other calls
// in the block - which is now split. so continue to traverse in the Tail
BBs.push_back(Tail);
}
}
// Erase everything we no longer need in this function
for (Instruction *I : ToErase)
I->eraseFromParent();
// Free setjmpTable buffer before each return instruction
for (BasicBlock &BB : F) {
TerminatorInst *TI = BB.getTerminator();
if (isa<ReturnInst>(TI))
CallInst::CreateFree(SetjmpTable, TI);
}
// Every call to saveSetjmp can change setjmpTable and setjmpTableSize
// (when buffer reallocation occurs)
// entry:
// setjmpTableSize = 4;
// setjmpTable = (int *) malloc(40);
// setjmpTable[0] = 0;
// ...
// somebb:
// setjmpTable = saveSetjmp(buf, label, setjmpTable, setjmpTableSize);
// setjmpTableSize = __tempRet0;
// So we need to make sure the SSA for these variables is valid so that every
// saveSetjmp and testSetjmp calls have the correct arguments.
SSAUpdater SetjmpTableSSA;
SSAUpdater SetjmpTableSizeSSA;
SetjmpTableSSA.Initialize(Type::getInt32PtrTy(C), "setjmpTable");
SetjmpTableSizeSSA.Initialize(Type::getInt32Ty(C), "setjmpTableSize");
for (Instruction *I : SetjmpTableInsts)
SetjmpTableSSA.AddAvailableValue(I->getParent(), I);
for (Instruction *I : SetjmpTableSizeInsts)
SetjmpTableSizeSSA.AddAvailableValue(I->getParent(), I);
for (auto UI = SetjmpTable->use_begin(), UE = SetjmpTable->use_end();
UI != UE;) {
// Grab the use before incrementing the iterator.
Use &U = *UI;
// Increment the iterator before removing the use from the list.
++UI;
if (Instruction *I = dyn_cast<Instruction>(U.getUser()))
if (I->getParent() != &EntryBB)
SetjmpTableSSA.RewriteUse(U);
}
for (auto UI = SetjmpTableSize->use_begin(), UE = SetjmpTableSize->use_end();
UI != UE;) {
Use &U = *UI;
++UI;
if (Instruction *I = dyn_cast<Instruction>(U.getUser()))
if (I->getParent() != &EntryBB)
SetjmpTableSizeSSA.RewriteUse(U);
}
// Finally, our modifications to the cfg can break dominance of SSA variables.
// For example, in this code,
// if (x()) { .. setjmp() .. }
// if (y()) { .. longjmp() .. }
// We must split the longjmp block, and it can jump into the block splitted
// from setjmp one. But that means that when we split the setjmp block, it's
// first part no longer dominates its second part - there is a theoretically
// possible control flow path where x() is false, then y() is true and we
// reach the second part of the setjmp block, without ever reaching the first
// part. So, we rebuild SSA form here.
rebuildSSA(F);
return true;
}
/// Given an instruction in the loop, check to see if it has any uses that are
/// outside the current loop. If so, insert LCSSA PHI nodes and rewrite the
/// uses.
static bool processInstruction(Loop &L, Instruction &Inst, DominatorTree &DT,
const SmallVectorImpl<BasicBlock *> &ExitBlocks,
PredIteratorCache &PredCache, LoopInfo *LI) {
SmallVector<Use *, 16> UsesToRewrite;
// Tokens cannot be used in PHI nodes, so we skip over them.
// We can run into tokens which are live out of a loop with catchswitch
// instructions in Windows EH if the catchswitch has one catchpad which
// is inside the loop and another which is not.
if (Inst.getType()->isTokenTy())
return false;
BasicBlock *InstBB = Inst.getParent();
for (Use &U : Inst.uses()) {
Instruction *User = cast<Instruction>(U.getUser());
BasicBlock *UserBB = User->getParent();
if (PHINode *PN = dyn_cast<PHINode>(User))
UserBB = PN->getIncomingBlock(U);
if (InstBB != UserBB && !L.contains(UserBB))
UsesToRewrite.push_back(&U);
}
// If there are no uses outside the loop, exit with no change.
if (UsesToRewrite.empty())
return false;
++NumLCSSA; // We are applying the transformation
// Invoke instructions are special in that their result value is not available
// along their unwind edge. The code below tests to see whether DomBB
// dominates the value, so adjust DomBB to the normal destination block,
// which is effectively where the value is first usable.
BasicBlock *DomBB = Inst.getParent();
if (InvokeInst *Inv = dyn_cast<InvokeInst>(&Inst))
DomBB = Inv->getNormalDest();
DomTreeNode *DomNode = DT.getNode(DomBB);
SmallVector<PHINode *, 16> AddedPHIs;
SmallVector<PHINode *, 8> PostProcessPHIs;
SSAUpdater SSAUpdate;
SSAUpdate.Initialize(Inst.getType(), Inst.getName());
// Insert the LCSSA phi's into all of the exit blocks dominated by the
// value, and add them to the Phi's map.
for (BasicBlock *ExitBB : ExitBlocks) {
if (!DT.dominates(DomNode, DT.getNode(ExitBB)))
continue;
// If we already inserted something for this BB, don't reprocess it.
if (SSAUpdate.HasValueForBlock(ExitBB))
continue;
PHINode *PN = PHINode::Create(Inst.getType(), PredCache.size(ExitBB),
Inst.getName() + ".lcssa", &ExitBB->front());
// Add inputs from inside the loop for this PHI.
for (BasicBlock *Pred : PredCache.get(ExitBB)) {
PN->addIncoming(&Inst, Pred);
// If the exit block has a predecessor not within the loop, arrange for
// the incoming value use corresponding to that predecessor to be
// rewritten in terms of a different LCSSA PHI.
if (!L.contains(Pred))
UsesToRewrite.push_back(
&PN->getOperandUse(PN->getOperandNumForIncomingValue(
PN->getNumIncomingValues() - 1)));
}
AddedPHIs.push_back(PN);
// Remember that this phi makes the value alive in this block.
SSAUpdate.AddAvailableValue(ExitBB, PN);
// LoopSimplify might fail to simplify some loops (e.g. when indirect
// branches are involved). In such situations, it might happen that an exit
// for Loop L1 is the header of a disjoint Loop L2. Thus, when we create
// PHIs in such an exit block, we are also inserting PHIs into L2's header.
// This could break LCSSA form for L2 because these inserted PHIs can also
// have uses outside of L2. Remember all PHIs in such situation as to
// revisit than later on. FIXME: Remove this if indirectbr support into
// LoopSimplify gets improved.
if (auto *OtherLoop = LI->getLoopFor(ExitBB))
if (!L.contains(OtherLoop))
PostProcessPHIs.push_back(PN);
}
// Rewrite all uses outside the loop in terms of the new PHIs we just
// inserted.
for (Use *UseToRewrite : UsesToRewrite) {
// If this use is in an exit block, rewrite to use the newly inserted PHI.
// This is required for correctness because SSAUpdate doesn't handle uses in
// the same block. It assumes the PHI we inserted is at the end of the
// block.
Instruction *User = cast<Instruction>(UseToRewrite->getUser());
BasicBlock *UserBB = User->getParent();
if (PHINode *PN = dyn_cast<PHINode>(User))
UserBB = PN->getIncomingBlock(*UseToRewrite);
if (isa<PHINode>(UserBB->begin()) && isExitBlock(UserBB, ExitBlocks)) {
// Tell the VHs that the uses changed. This updates SCEV's caches.
if (UseToRewrite->get()->hasValueHandle())
ValueHandleBase::ValueIsRAUWd(*UseToRewrite, &UserBB->front());
UseToRewrite->set(&UserBB->front());
continue;
}
// Otherwise, do full PHI insertion.
SSAUpdate.RewriteUse(*UseToRewrite);
}
// Post process PHI instructions that were inserted into another disjoint loop
// and update their exits properly.
for (auto *I : PostProcessPHIs) {
if (I->use_empty())
continue;
BasicBlock *PHIBB = I->getParent();
Loop *OtherLoop = LI->getLoopFor(PHIBB);
SmallVector<BasicBlock *, 8> EBs;
OtherLoop->getExitBlocks(EBs);
if (EBs.empty())
continue;
// Recurse and re-process each PHI instruction. FIXME: we should really
// convert this entire thing to a worklist approach where we process a
// vector of instructions...
processInstruction(*OtherLoop, *I, DT, EBs, PredCache, LI);
}
// Remove PHI nodes that did not have any uses rewritten.
for (PHINode *PN : AddedPHIs)
if (PN->use_empty())
PN->eraseFromParent();
return true;
}
