static SILValue getIncomingValueForPred(SILBasicBlock *BB, SILBasicBlock *Pred,
unsigned Index) {
TermInst *TI = Pred->getTerminator();
switch (TI->getTermKind()) {
// TODO: This list is conservative. I think we can probably handle more of
// these.
case TermKind::UnreachableInst:
case TermKind::ReturnInst:
case TermKind::ThrowInst:
case TermKind::TryApplyInst:
case TermKind::SwitchValueInst:
case TermKind::SwitchEnumAddrInst:
case TermKind::CheckedCastAddrBranchInst:
case TermKind::DynamicMethodBranchInst:
return SILValue();
case TermKind::BranchInst:
return cast<BranchInst>(TI)->getArg(Index);
case TermKind::CondBranchInst:
return cast<CondBranchInst>(TI)->getArgForDestBB(BB, Index);
case TermKind::CheckedCastBranchInst:
return cast<CheckedCastBranchInst>(TI)->getOperand();
case TermKind::SwitchEnumInst:
return cast<SwitchEnumInst>(TI)->getOperand();
}
llvm_unreachable("Unhandled TermKind?!");
}
void StackAllocationPromoter::fixPhiPredBlock(BlockSet &PhiBlocks,
SILBasicBlock *Dest,
SILBasicBlock *Pred) {
TermInst *TI = Pred->getTerminator();
DEBUG(llvm::dbgs() << "*** Fixing the terminator " << TI << ".\n");
SILValue Def = getLiveOutValue(PhiBlocks, Pred);
DEBUG(llvm::dbgs() << "*** Found the definition: " << *Def);
addArgumentToBranch(Def, Dest, TI);
TI->eraseFromParent();
}
/// Emit dealloc_stack for all temporaries.
void PartialApplyCombiner::deallocateTemporaries() {
// Insert dealloc_stack instructions at all function exit points.
for (SILBasicBlock &BB : *PAI->getFunction()) {
TermInst *Term = BB.getTerminator();
if (!Term->isFunctionExiting())
continue;
for (auto Op : Tmps) {
Builder.setInsertionPoint(Term);
Builder.createDeallocStack(PAI->getLoc(), Op);
}
}
}
/// \brief Adds a new argument to an edge between a branch and a destination
/// block.
///
/// \param Branch The terminator to add the argument to.
/// \param Dest The destination block of the edge.
/// \param Val The value to the arguments of the branch.
/// \return The created branch. The old branch is deleted.
/// The argument is appended at the end of the argument tuple.
TermInst *swift::addNewEdgeValueToBranch(TermInst *Branch, SILBasicBlock *Dest,
SILValue Val) {
SILBuilderWithScope Builder(Branch);
TermInst *NewBr = nullptr;
if (CondBranchInst *CBI = dyn_cast<CondBranchInst>(Branch)) {
SmallVector<SILValue, 8> TrueArgs;
SmallVector<SILValue, 8> FalseArgs;
for (auto A : CBI->getTrueArgs())
TrueArgs.push_back(A);
for (auto A : CBI->getFalseArgs())
FalseArgs.push_back(A);
if (Dest == CBI->getTrueBB()) {
TrueArgs.push_back(Val);
assert(TrueArgs.size() == Dest->getNumBBArg());
}
if (Dest == CBI->getFalseBB()) {
FalseArgs.push_back(Val);
assert(FalseArgs.size() == Dest->getNumBBArg());
}
NewBr = Builder.createCondBranch(CBI->getLoc(), CBI->getCondition(),
CBI->getTrueBB(), TrueArgs,
CBI->getFalseBB(), FalseArgs);
} else if (BranchInst *BI = dyn_cast<BranchInst>(Branch)) {
SmallVector<SILValue, 8> Args;
for (auto A : BI->getArgs())
Args.push_back(A);
Args.push_back(Val);
assert(Args.size() == Dest->getNumBBArg());
NewBr = Builder.createBranch(BI->getLoc(), BI->getDestBB(), Args);
} else {
NewBr->dump();
// At the moment we can only add arguments to br and cond_br.
llvm_unreachable("Can't add argument to terminator");
return NewBr;
}
Branch->dropAllReferences();
Branch->eraseFromParent();
return NewBr;
}
bool StackPromoter::promote() {
llvm::SetVector<SILBasicBlock *> ReachableBlocks;
// First step: find blocks which end up in a no-return block (terminated by
// an unreachable instruction).
// Search for function-exiting blocks, i.e. return and throw.
for (SILBasicBlock &BB : *F) {
TermInst *TI = BB.getTerminator();
if (TI->isFunctionExiting())
ReachableBlocks.insert(&BB);
}
// Propagate the reachability up the control flow graph.
unsigned Idx = 0;
while (Idx < ReachableBlocks.size()) {
SILBasicBlock *BB = ReachableBlocks[Idx++];
for (SILBasicBlock *Pred : BB->getPredecessorBlocks())
ReachableBlocks.insert(Pred);
}
bool Changed = false;
// Search the whole function for stack promotable allocations.
for (SILBasicBlock &BB : *F) {
// Don't stack promote any allocation inside a code region which ends up in
// a no-return block. Such allocations may missing their final release.
// We would insert the deallocation too early, which may result in a
// use-after-free problem.
if (ReachableBlocks.count(&BB) == 0)
continue;
for (auto Iter = BB.begin(); Iter != BB.end();) {
// The allocation instruction may be moved, so increment Iter prior to
// doing the optimization.
SILInstruction *I = &*Iter++;
if (auto *ARI = dyn_cast<AllocRefInst>(I)) {
Changed |= tryPromoteAlloc(ARI);
}
}
}
return Changed;
}
/// We rotated a loop if it has the following properties.
///
/// * It has an exiting header with a conditional branch.
/// * It has a preheader (the function will try to create one for critical edges
/// from cond_br).
///
/// We will rotate at most up to the basic block passed as an argument.
/// We will not rotate a loop where the header is equal to the latch except is
/// RotateSingleBlockLoops is true.
///
/// Note: The code relies on the 'UpTo' basic block to stay within the rotate
/// loop for termination.
bool swift::rotateLoop(SILLoop *L, DominanceInfo *DT, SILLoopInfo *LI,
bool RotateSingleBlockLoops, SILBasicBlock *UpTo,
bool ShouldVerify) {
assert(L != nullptr && DT != nullptr && LI != nullptr &&
"Missing loop information");
auto *Header = L->getHeader();
if (!Header)
return false;
// We need a preheader - this is also a canonicalization for follow-up
// passes.
auto *Preheader = L->getLoopPreheader();
if (!Preheader) {
LLVM_DEBUG(llvm::dbgs() << *L << " no preheader\n");
LLVM_DEBUG(L->getHeader()->getParent()->dump());
return false;
}
if (!RotateSingleBlockLoops && (Header == UpTo || isSingleBlockLoop(L)))
return false;
assert(RotateSingleBlockLoops || L->getBlocks().size() != 1);
// Need a conditional branch that guards the entry into the loop.
auto *LoopEntryBranch = dyn_cast<CondBranchInst>(Header->getTerminator());
if (!LoopEntryBranch)
return false;
// The header needs to exit the loop.
if (!L->isLoopExiting(Header)) {
LLVM_DEBUG(llvm::dbgs() << *L << " not an exiting header\n");
LLVM_DEBUG(L->getHeader()->getParent()->dump());
return false;
}
// We need a single backedge and the latch must not exit the loop if it is
// also the header.
auto *Latch = L->getLoopLatch();
if (!Latch) {
LLVM_DEBUG(llvm::dbgs() << *L << " no single latch\n");
return false;
}
// Make sure we can duplicate the header.
SmallVector<SILInstruction *, 8> MoveToPreheader;
if (!canDuplicateOrMoveToPreheader(L, Preheader, Header, MoveToPreheader)) {
LLVM_DEBUG(llvm::dbgs() << *L
<< " instructions in header preventing rotating\n");
return false;
}
auto *NewHeader = LoopEntryBranch->getTrueBB();
auto *Exit = LoopEntryBranch->getFalseBB();
if (L->contains(Exit))
std::swap(NewHeader, Exit);
assert(L->contains(NewHeader) && !L->contains(Exit) &&
"Could not find loop header and exit block");
// We don't want to rotate such that we merge two headers of separate loops
// into one. This can be turned into an assert again once we have guaranteed
// preheader insertions.
if (!NewHeader->getSinglePredecessorBlock() && Header != Latch)
return false;
// Now that we know we can perform the rotation - move the instructions that
// need moving.
for (auto *Inst : MoveToPreheader)
Inst->moveBefore(Preheader->getTerminator());
LLVM_DEBUG(llvm::dbgs() << " Rotating " << *L);
// Map the values for the duplicated header block. We are duplicating the
// header instructions into the end of the preheader.
llvm::DenseMap<ValueBase *, SILValue> ValueMap;
// The original 'phi' argument values are just the values coming from the
// preheader edge.
ArrayRef<SILArgument *> PHIs = Header->getArguments();
OperandValueArrayRef PreheaderArgs =
cast<BranchInst>(Preheader->getTerminator())->getArgs();
assert(PHIs.size() == PreheaderArgs.size() &&
"Basic block arguments and incoming edge mismatch");
// Here we also store the value index to use into the value map (versus
// non-argument values where the operand use decides which value index to
// use).
for (unsigned Idx = 0, E = PHIs.size(); Idx != E; ++Idx)
ValueMap[PHIs[Idx]] = PreheaderArgs[Idx];
// The other instructions are just cloned to the preheader.
TermInst *PreheaderBranch = Preheader->getTerminator();
for (auto &Inst : *Header) {
if (SILInstruction *cloned = Inst.clone(PreheaderBranch)) {
mapOperands(cloned, ValueMap);
// The actual operand will sort out which result idx to use.
auto instResults = Inst.getResults();
auto clonedResults = cloned->getResults();
assert(instResults.size() == clonedResults.size());
for (auto i : indices(instResults))
ValueMap[instResults[i]] = clonedResults[i];
}
}
PreheaderBranch->dropAllReferences();
PreheaderBranch->eraseFromParent();
// If there were any uses of instructions in the duplicated loop entry check
// block rewrite them using the ssa updater.
rewriteNewLoopEntryCheckBlock(Header, Preheader, ValueMap);
L->moveToHeader(NewHeader);
// Now the original preheader dominates all of headers children and the
// original latch dominates the header.
updateDomTree(DT, Preheader, Latch, Header);
assert(DT->getNode(NewHeader)->getIDom() == DT->getNode(Preheader));
assert(!DT->dominates(Header, Exit) ||
DT->getNode(Exit)->getIDom() == DT->getNode(Preheader));
assert(DT->getNode(Header)->getIDom() == DT->getNode(Latch) ||
((Header == Latch) &&
DT->getNode(Header)->getIDom() == DT->getNode(Preheader)));
// Beautify the IR. Move the old header to after the old latch as it is now
// the latch.
Header->moveAfter(Latch);
// Merge the old latch with the old header if possible.
mergeBasicBlockWithSuccessor(Latch, DT, LI);
// Create a new preheader.
splitIfCriticalEdge(Preheader, NewHeader, DT, LI);
if (ShouldVerify) {
DT->verify();
LI->verify();
Latch->getParent()->verify();
}
LLVM_DEBUG(llvm::dbgs() << " to " << *L);
LLVM_DEBUG(L->getHeader()->getParent()->dump());
return true;
}
static bool constantFoldTerminator(SILBasicBlock &BB,
UnreachableUserCodeReportingState *State) {
TermInst *TI = BB.getTerminator();
// Process conditional branches with constant conditions.
if (CondBranchInst *CBI = dyn_cast<CondBranchInst>(TI)) {
SILValue V = CBI->getCondition();
SILInstruction *CondI = dyn_cast<SILInstruction>(V);
SILLocation Loc = CBI->getLoc();
if (IntegerLiteralInst *ConstCond =
dyn_cast_or_null<IntegerLiteralInst>(CondI)) {
SILBuilderWithScope B(&BB, CBI);
// Determine which of the successors is unreachable and create a new
// terminator that only branches to the reachable successor.
SILBasicBlock *UnreachableBlock = nullptr;
bool CondIsTrue = false;
if (ConstCond->getValue() == APInt(1, /*value*/ 0, false)) {
B.createBranch(Loc, CBI->getFalseBB(), CBI->getFalseArgs());
UnreachableBlock = CBI->getTrueBB();
} else {
assert(ConstCond->getValue() == APInt(1, /*value*/ 1, false) &&
"Our representation of true/false does not match.");
B.createBranch(Loc, CBI->getTrueBB(), CBI->getTrueArgs());
UnreachableBlock = CBI->getFalseBB();
CondIsTrue = true;
}
recursivelyDeleteTriviallyDeadInstructions(TI, true);
NumInstructionsRemoved++;
// Produce an unreachable code warning for this basic block if it
// contains user code (only if we are not within an inlined function or a
// template instantiation).
// FIXME: Do not report if we are within a template instantiation.
if (Loc.is<RegularLocation>() && State &&
!State->PossiblyUnreachableBlocks.count(UnreachableBlock)) {
// If this is the first time we see this unreachable block, store it
// along with the folded branch info.
State->PossiblyUnreachableBlocks.insert(UnreachableBlock);
State->MetaMap.insert(
std::pair<const SILBasicBlock*, UnreachableInfo>(
UnreachableBlock,
UnreachableInfo{UnreachableKind::FoldedBranch, Loc, CondIsTrue}));
}
NumTerminatorsFolded++;
return true;
}
}
// Constant fold switch enum.
// %1 = enum $Bool, #Bool.false!unionelt
// switch_enum %1 : $Bool, case #Bool.true!unionelt: bb1,
// case #Bool.false!unionelt: bb2
// =>
// br bb2
if (SwitchEnumInst *SUI = dyn_cast<SwitchEnumInst>(TI)) {
if (EnumInst *TheEnum = dyn_cast<EnumInst>(SUI->getOperand())) {
const EnumElementDecl *TheEnumElem = TheEnum->getElement();
SILBasicBlock *TheSuccessorBlock = nullptr;
int ReachableBlockIdx = -1;
for (unsigned Idx = 0; Idx < SUI->getNumCases(); ++Idx) {
const EnumElementDecl *EI;
SILBasicBlock *BI;
std::tie(EI, BI) = SUI->getCase(Idx);
if (EI == TheEnumElem) {
TheSuccessorBlock = BI;
ReachableBlockIdx = Idx;
break;
}
}
if (!TheSuccessorBlock)
if (SUI->hasDefault()) {
SILBasicBlock *DB= SUI->getDefaultBB();
if (!isa<UnreachableInst>(DB->getTerminator())) {
TheSuccessorBlock = DB;
ReachableBlockIdx = SUI->getNumCases();
}
}
// Not fully covered switches will be diagnosed later. SILGen represents
// them with a Default basic block with an unrechable instruction.
// We are going to produce an error on all unreachable instructions not
// eliminated by DCE.
if (!TheSuccessorBlock)
return false;
// Replace the switch with a branch to the TheSuccessorBlock.
SILBuilderWithScope B(&BB, TI);
SILLocation Loc = TI->getLoc();
if (!TheSuccessorBlock->bbarg_empty()) {
assert(TheEnum->hasOperand());
B.createBranch(Loc, TheSuccessorBlock, TheEnum->getOperand());
} else
B.createBranch(Loc, TheSuccessorBlock);
// Produce diagnostic info if we are not within an inlined function or
// template instantiation.
// FIXME: Do not report if we are within a template instantiation.
assert(ReachableBlockIdx >= 0);
if (Loc.is<RegularLocation>() && State) {
// Find the first unreachable block in the switch so that we could use
// it for better diagnostics.
SILBasicBlock *UnreachableBlock = nullptr;
if (SUI->getNumCases() > 1) {
// More than one case.
UnreachableBlock =
(ReachableBlockIdx == 0) ? SUI->getCase(1).second:
SUI->getCase(0).second;
} else {
if (SUI->getNumCases() == 1 && SUI->hasDefault()) {
// One case and a default.
UnreachableBlock =
(ReachableBlockIdx == 0) ? SUI->getDefaultBB():
SUI->getCase(0).second;
}
}
// Generate diagnostic info.
if (UnreachableBlock &&
!State->PossiblyUnreachableBlocks.count(UnreachableBlock)) {
State->PossiblyUnreachableBlocks.insert(UnreachableBlock);
State->MetaMap.insert(
std::pair<const SILBasicBlock*, UnreachableInfo>(
UnreachableBlock,
UnreachableInfo{UnreachableKind::FoldedSwitchEnum, Loc, true}));
}
}
recursivelyDeleteTriviallyDeadInstructions(TI, true);
NumTerminatorsFolded++;
return true;
}
}
// Constant fold switch int.
// %1 = integer_literal $Builtin.Int64, 2
// switch_value %1 : $Builtin.Int64, case 1: bb1, case 2: bb2
// =>
// br bb2
if (SwitchValueInst *SUI = dyn_cast<SwitchValueInst>(TI)) {
if (IntegerLiteralInst *SwitchVal =
dyn_cast<IntegerLiteralInst>(SUI->getOperand())) {
SILBasicBlock *TheSuccessorBlock = 0;
for (unsigned Idx = 0; Idx < SUI->getNumCases(); ++Idx) {
APInt AI;
SILValue EI;
SILBasicBlock *BI;
std::tie(EI, BI) = SUI->getCase(Idx);
// TODO: Check that EI is really an IntegerLiteralInst
AI = dyn_cast<IntegerLiteralInst>(EI)->getValue();
if (AI == SwitchVal->getValue())
TheSuccessorBlock = BI;
}
if (!TheSuccessorBlock)
if (SUI->hasDefault())
TheSuccessorBlock = SUI->getDefaultBB();
// Add the branch instruction with the block.
if (TheSuccessorBlock) {
SILBuilderWithScope B(&BB, TI);
B.createBranch(TI->getLoc(), TheSuccessorBlock);
recursivelyDeleteTriviallyDeadInstructions(TI, true);
NumTerminatorsFolded++;
return true;
}
// TODO: Warn on unreachable user code here as well.
}
}
return false;
}
/// \brief Populate the body of the cloned closure, modifying instructions as
/// necessary. This is where we create the actual specialized BB Arguments.
void ClosureSpecCloner::populateCloned() {
SILFunction *Cloned = getCloned();
SILFunction *ClosureUser = CallSiteDesc.getApplyCallee();
// Create arguments for the entry block.
SILBasicBlock *ClosureUserEntryBB = &*ClosureUser->begin();
SILBasicBlock *ClonedEntryBB = Cloned->createBasicBlock();
SmallVector<SILValue, 4> entryArgs;
entryArgs.reserve(ClosureUserEntryBB->getArguments().size());
// Remove the closure argument.
SILArgument *ClosureArg = nullptr;
for (size_t i = 0, e = ClosureUserEntryBB->args_size(); i != e; ++i) {
SILArgument *Arg = ClosureUserEntryBB->getArgument(i);
if (i == CallSiteDesc.getClosureIndex()) {
ClosureArg = Arg;
entryArgs.push_back(SILValue());
continue;
}
// Otherwise, create a new argument which copies the original argument
SILValue MappedValue =
ClonedEntryBB->createFunctionArgument(Arg->getType(), Arg->getDecl());
entryArgs.push_back(MappedValue);
}
// Next we need to add in any arguments that are not captured as arguments to
// the cloned function.
//
// We do not insert the new mapped arguments into the value map since there by
// definition is nothing in the partial apply user function that references
// such arguments. After this pass is done the only thing that will reference
// the arguments is the partial apply that we will create.
SILFunction *ClosedOverFun = CallSiteDesc.getClosureCallee();
auto ClosedOverFunConv = ClosedOverFun->getConventions();
unsigned NumTotalParams = ClosedOverFunConv.getNumParameters();
unsigned NumNotCaptured = NumTotalParams - CallSiteDesc.getNumArguments();
llvm::SmallVector<SILValue, 4> NewPAIArgs;
for (auto &PInfo : ClosedOverFunConv.getParameters().slice(NumNotCaptured)) {
auto paramTy = ClosedOverFunConv.getSILType(PInfo);
SILValue MappedValue = ClonedEntryBB->createFunctionArgument(paramTy);
NewPAIArgs.push_back(MappedValue);
}
SILBuilder &Builder = getBuilder();
Builder.setInsertionPoint(ClonedEntryBB);
// Clone FRI and PAI, and replace usage of the removed closure argument
// with result of cloned PAI.
SILValue FnVal =
Builder.createFunctionRef(CallSiteDesc.getLoc(), ClosedOverFun);
auto *NewClosure = CallSiteDesc.createNewClosure(Builder, FnVal, NewPAIArgs);
// Clone a chain of ConvertFunctionInsts. This can create further
// reabstraction partial_apply instructions.
SmallVector<PartialApplyInst*, 4> NeedsRelease;
SILValue ConvertedCallee = cloneCalleeConversion(
CallSiteDesc.getClosureCallerArg(), NewClosure, Builder, NeedsRelease);
// Make sure that we actually emit the releases for reabstraction thunks. We
// have guaranteed earlier that we only allow reabstraction thunks if the
// closure was passed trivial.
assert(NeedsRelease.empty() || CallSiteDesc.isTrivialNoEscapeParameter());
entryArgs[CallSiteDesc.getClosureIndex()] = ConvertedCallee;
// Visit original BBs in depth-first preorder, starting with the
// entry block, cloning all instructions and terminators.
cloneFunctionBody(ClosureUser, ClonedEntryBB, entryArgs);
// Then insert a release in all non failure exit BBs if our partial apply was
// guaranteed. This is b/c it was passed at +0 originally and we need to
// balance the initial increment of the newly created closure(s).
bool ClosureHasRefSemantics = CallSiteDesc.closureHasRefSemanticContext();
if ((CallSiteDesc.isClosureGuaranteed() ||
CallSiteDesc.isTrivialNoEscapeParameter()) &&
(ClosureHasRefSemantics || !NeedsRelease.empty())) {
for (SILBasicBlock *BB : CallSiteDesc.getNonFailureExitBBs()) {
SILBasicBlock *OpBB = getOpBasicBlock(BB);
TermInst *TI = OpBB->getTerminator();
auto Loc = CleanupLocation::get(NewClosure->getLoc());
// If we have an exit, we place the release right before it so we know
// that it will be executed at the end of the epilogue.
if (TI->isFunctionExiting()) {
Builder.setInsertionPoint(TI);
if (ClosureHasRefSemantics)
Builder.createReleaseValue(Loc, SILValue(NewClosure),
Builder.getDefaultAtomicity());
for (auto PAI : NeedsRelease)
Builder.createReleaseValue(Loc, SILValue(PAI),
Builder.getDefaultAtomicity());
continue;
}
// We use casts where findAllNonFailureExitBBs should have made sure that
// this is true. This will ensure that the code is updated when we hit the
// cast failure in debug builds.
auto *Unreachable = cast<UnreachableInst>(TI);
auto PrevIter = std::prev(SILBasicBlock::iterator(Unreachable));
auto NoReturnApply = FullApplySite::isa(&*PrevIter);
// We insert the release value right before the no return apply so that if
// the partial apply is passed into the no-return function as an @owned
// value, we will retain the partial apply before we release it and
// potentially eliminate it.
Builder.setInsertionPoint(NoReturnApply.getInstruction());
if (ClosureHasRefSemantics)
Builder.createReleaseValue(Loc, SILValue(NewClosure),
Builder.getDefaultAtomicity());
for (auto PAI : NeedsRelease)
Builder.createReleaseValue(Loc, SILValue(PAI),
Builder.getDefaultAtomicity());
}
}
}
// Attempt to insert a new access in the loop preheader. If successful, insert
// the new access in DominatedAccessAnalysis so it can be used to dominate other
// accesses. Also convert the current access to static and update the current
// storageToDomMap since the access may already have been recorded (when it was
// still dynamic).
//
// This function cannot add or remove instructions in the current block, but
// may add instructions to the current loop's preheader.
//
// The required conditions for inserting a new dominating access are:
//
// 1. The new preheader access is not enclosed in another scope that doesn't
// also enclose the current scope.
//
// This is inferred from the loop structure; any scope that encloses the
// preheader must also enclose the entire loop.
//
// 2. The current access is not enclosed in another scope that doesn't also
// enclose the preheader.
//
// As before, it is sufficient to check this access' isInner flags in
// DominatedAccessAnalysis; if this access isn't enclosed by any scope within
// the function, then it can't be enclosed within a scope inside the loop.
//
// 3. The current header has no nested conflict within its scope.
//
// 4. The access' source operand is available in the loop preheader.
void DominatedAccessRemoval::tryInsertLoopPreheaderAccess(
BeginAccessInst *BAI, DomAccessedStorage currAccessInfo) {
// 2. the current access may be enclosed.
if (currAccessInfo.isInner())
return;
// 3. the current access must be instantaneous.
if (!BAI->hasNoNestedConflict())
return;
SILLoop *currLoop = loopInfo->getLoopFor(BAI->getParent());
if (!currLoop)
return;
SILBasicBlock *preheader = currLoop->getLoopPreheader();
if (!preheader)
return;
// 4. The source operand must be available in the preheader.
auto sourceOperand = BAI->getOperand();
auto *sourceBB = sourceOperand->getParentBlock();
if (!domInfo->dominates(sourceBB, preheader))
return;
// Insert a new access scope immediately before the
// preheader's terminator.
TermInst *preheaderTerm = preheader->getTerminator();
SILBuilderWithScope scopeBuilder(preheaderTerm);
BeginAccessInst *newBegin = scopeBuilder.createBeginAccess(
preheaderTerm->getLoc(), sourceOperand, BAI->getAccessKind(),
SILAccessEnforcement::Dynamic, true /*no nested conflict*/,
BAI->isFromBuiltin());
scopeBuilder.createEndAccess(preheaderTerm->getLoc(), newBegin, false);
LLVM_DEBUG(llvm::dbgs() << "Created loop preheader access: " << *newBegin
<< "\n"
<< "dominating: " << *BAI << "\n");
BAI->setEnforcement(SILAccessEnforcement::Static);
hasChanged = true;
// Insert the new dominating instruction in both DominatedAccessAnalysis and
// storageToDomMap if it has uniquely identifiable storage.
if (!currAccessInfo.isUniquelyIdentifiedOrClass())
return;
AccessedStorage storage = static_cast<AccessedStorage>(currAccessInfo);
storage.resetSubclassData();
// Create a DomAccessedStorage for the new access with no flags set.
DAA.accessMap.try_emplace(newBegin, DomAccessedStorage(storage));
// Track the new access as long as no other accesses from the same storage are
// already tracked. This also necessarily replaces the current access, which
// was just made static.
DominatingAccess newDomAccess(newBegin, domInfo->getNode(preheader));
auto iterAndInserted = storageToDomMap.try_emplace(storage, newDomAccess);
if (!iterAndInserted.second) {
DominatingAccess &curDomAccess = iterAndInserted.first->second;
if (curDomAccess.beginAccess == BAI)
curDomAccess = newDomAccess;
}
}